diff options
Diffstat (limited to 'net/ipv4/tcp_output.c')
| -rw-r--r-- | net/ipv4/tcp_output.c | 4199 |
1 files changed, 4199 insertions, 0 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c new file mode 100644 index 000000000..67087da45 --- /dev/null +++ b/net/ipv4/tcp_output.c @@ -0,0 +1,4199 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * INET An implementation of the TCP/IP protocol suite for the LINUX + * operating system. INET is implemented using the BSD Socket + * interface as the means of communication with the user level. + * + * Implementation of the Transmission Control Protocol(TCP). + * + * Authors: Ross Biro + * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> + * Mark Evans, <evansmp@uhura.aston.ac.uk> + * Corey Minyard <wf-rch!minyard@relay.EU.net> + * Florian La Roche, <flla@stud.uni-sb.de> + * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> + * Linus Torvalds, <torvalds@cs.helsinki.fi> + * Alan Cox, <gw4pts@gw4pts.ampr.org> + * Matthew Dillon, <dillon@apollo.west.oic.com> + * Arnt Gulbrandsen, <agulbra@nvg.unit.no> + * Jorge Cwik, <jorge@laser.satlink.net> + */ + +/* + * Changes: Pedro Roque : Retransmit queue handled by TCP. + * : Fragmentation on mtu decrease + * : Segment collapse on retransmit + * : AF independence + * + * Linus Torvalds : send_delayed_ack + * David S. Miller : Charge memory using the right skb + * during syn/ack processing. + * David S. Miller : Output engine completely rewritten. + * Andrea Arcangeli: SYNACK carry ts_recent in tsecr. + * Cacophonix Gaul : draft-minshall-nagle-01 + * J Hadi Salim : ECN support + * + */ + +#define pr_fmt(fmt) "TCP: " fmt + +#include <net/tcp.h> +#include <net/mptcp.h> + +#include <linux/compiler.h> +#include <linux/gfp.h> +#include <linux/module.h> +#include <linux/static_key.h> + +#include <trace/events/tcp.h> + +/* Refresh clocks of a TCP socket, + * ensuring monotically increasing values. + */ +void tcp_mstamp_refresh(struct tcp_sock *tp) +{ + u64 val = tcp_clock_ns(); + + tp->tcp_clock_cache = val; + tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC); +} + +static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, + int push_one, gfp_t gfp); + +/* Account for new data that has been sent to the network. */ +static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + unsigned int prior_packets = tp->packets_out; + + WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq); + + __skb_unlink(skb, &sk->sk_write_queue); + tcp_rbtree_insert(&sk->tcp_rtx_queue, skb); + + if (tp->highest_sack == NULL) + tp->highest_sack = skb; + + tp->packets_out += tcp_skb_pcount(skb); + if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) + tcp_rearm_rto(sk); + + NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT, + tcp_skb_pcount(skb)); + tcp_check_space(sk); +} + +/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one + * window scaling factor due to loss of precision. + * If window has been shrunk, what should we make? It is not clear at all. + * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( + * Anything in between SND.UNA...SND.UNA+SND.WND also can be already + * invalid. OK, let's make this for now: + */ +static inline __u32 tcp_acceptable_seq(const struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + if (!before(tcp_wnd_end(tp), tp->snd_nxt) || + (tp->rx_opt.wscale_ok && + ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale)))) + return tp->snd_nxt; + else + return tcp_wnd_end(tp); +} + +/* Calculate mss to advertise in SYN segment. + * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: + * + * 1. It is independent of path mtu. + * 2. Ideally, it is maximal possible segment size i.e. 65535-40. + * 3. For IPv4 it is reasonable to calculate it from maximal MTU of + * attached devices, because some buggy hosts are confused by + * large MSS. + * 4. We do not make 3, we advertise MSS, calculated from first + * hop device mtu, but allow to raise it to ip_rt_min_advmss. + * This may be overridden via information stored in routing table. + * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, + * probably even Jumbo". + */ +static __u16 tcp_advertise_mss(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + const struct dst_entry *dst = __sk_dst_get(sk); + int mss = tp->advmss; + + if (dst) { + unsigned int metric = dst_metric_advmss(dst); + + if (metric < mss) { + mss = metric; + tp->advmss = mss; + } + } + + return (__u16)mss; +} + +/* RFC2861. Reset CWND after idle period longer RTO to "restart window". + * This is the first part of cwnd validation mechanism. + */ +void tcp_cwnd_restart(struct sock *sk, s32 delta) +{ + struct tcp_sock *tp = tcp_sk(sk); + u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk)); + u32 cwnd = tcp_snd_cwnd(tp); + + tcp_ca_event(sk, CA_EVENT_CWND_RESTART); + + tp->snd_ssthresh = tcp_current_ssthresh(sk); + restart_cwnd = min(restart_cwnd, cwnd); + + while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd) + cwnd >>= 1; + tcp_snd_cwnd_set(tp, max(cwnd, restart_cwnd)); + tp->snd_cwnd_stamp = tcp_jiffies32; + tp->snd_cwnd_used = 0; +} + +/* Congestion state accounting after a packet has been sent. */ +static void tcp_event_data_sent(struct tcp_sock *tp, + struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + const u32 now = tcp_jiffies32; + + if (tcp_packets_in_flight(tp) == 0) + tcp_ca_event(sk, CA_EVENT_TX_START); + + tp->lsndtime = now; + + /* If it is a reply for ato after last received + * packet, enter pingpong mode. + */ + if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato) + inet_csk_enter_pingpong_mode(sk); +} + +/* Account for an ACK we sent. */ +static inline void tcp_event_ack_sent(struct sock *sk, u32 rcv_nxt) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (unlikely(tp->compressed_ack)) { + NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED, + tp->compressed_ack); + tp->compressed_ack = 0; + if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1) + __sock_put(sk); + } + + if (unlikely(rcv_nxt != tp->rcv_nxt)) + return; /* Special ACK sent by DCTCP to reflect ECN */ + tcp_dec_quickack_mode(sk); + inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); +} + +/* Determine a window scaling and initial window to offer. + * Based on the assumption that the given amount of space + * will be offered. Store the results in the tp structure. + * NOTE: for smooth operation initial space offering should + * be a multiple of mss if possible. We assume here that mss >= 1. + * This MUST be enforced by all callers. + */ +void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss, + __u32 *rcv_wnd, __u32 *window_clamp, + int wscale_ok, __u8 *rcv_wscale, + __u32 init_rcv_wnd) +{ + unsigned int space = (__space < 0 ? 0 : __space); + + /* If no clamp set the clamp to the max possible scaled window */ + if (*window_clamp == 0) + (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE); + space = min(*window_clamp, space); + + /* Quantize space offering to a multiple of mss if possible. */ + if (space > mss) + space = rounddown(space, mss); + + /* NOTE: offering an initial window larger than 32767 + * will break some buggy TCP stacks. If the admin tells us + * it is likely we could be speaking with such a buggy stack + * we will truncate our initial window offering to 32K-1 + * unless the remote has sent us a window scaling option, + * which we interpret as a sign the remote TCP is not + * misinterpreting the window field as a signed quantity. + */ + if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)) + (*rcv_wnd) = min(space, MAX_TCP_WINDOW); + else + (*rcv_wnd) = min_t(u32, space, U16_MAX); + + if (init_rcv_wnd) + *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss); + + *rcv_wscale = 0; + if (wscale_ok) { + /* Set window scaling on max possible window */ + space = max_t(u32, space, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2])); + space = max_t(u32, space, READ_ONCE(sysctl_rmem_max)); + space = min_t(u32, space, *window_clamp); + *rcv_wscale = clamp_t(int, ilog2(space) - 15, + 0, TCP_MAX_WSCALE); + } + /* Set the clamp no higher than max representable value */ + (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp); +} +EXPORT_SYMBOL(tcp_select_initial_window); + +/* Chose a new window to advertise, update state in tcp_sock for the + * socket, and return result with RFC1323 scaling applied. The return + * value can be stuffed directly into th->window for an outgoing + * frame. + */ +static u16 tcp_select_window(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + u32 old_win = tp->rcv_wnd; + u32 cur_win = tcp_receive_window(tp); + u32 new_win = __tcp_select_window(sk); + struct net *net = sock_net(sk); + + if (new_win < cur_win) { + /* Danger Will Robinson! + * Don't update rcv_wup/rcv_wnd here or else + * we will not be able to advertise a zero + * window in time. --DaveM + * + * Relax Will Robinson. + */ + if (!READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) || !tp->rx_opt.rcv_wscale) { + /* Never shrink the offered window */ + if (new_win == 0) + NET_INC_STATS(net, LINUX_MIB_TCPWANTZEROWINDOWADV); + new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale); + } + } + + tp->rcv_wnd = new_win; + tp->rcv_wup = tp->rcv_nxt; + + /* Make sure we do not exceed the maximum possible + * scaled window. + */ + if (!tp->rx_opt.rcv_wscale && + READ_ONCE(net->ipv4.sysctl_tcp_workaround_signed_windows)) + new_win = min(new_win, MAX_TCP_WINDOW); + else + new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); + + /* RFC1323 scaling applied */ + new_win >>= tp->rx_opt.rcv_wscale; + + /* If we advertise zero window, disable fast path. */ + if (new_win == 0) { + tp->pred_flags = 0; + if (old_win) + NET_INC_STATS(net, LINUX_MIB_TCPTOZEROWINDOWADV); + } else if (old_win == 0) { + NET_INC_STATS(net, LINUX_MIB_TCPFROMZEROWINDOWADV); + } + + return new_win; +} + +/* Packet ECN state for a SYN-ACK */ +static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR; + if (!(tp->ecn_flags & TCP_ECN_OK)) + TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE; + else if (tcp_ca_needs_ecn(sk) || + tcp_bpf_ca_needs_ecn(sk)) + INET_ECN_xmit(sk); +} + +/* Packet ECN state for a SYN. */ +static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk); + bool use_ecn = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn) == 1 || + tcp_ca_needs_ecn(sk) || bpf_needs_ecn; + + if (!use_ecn) { + const struct dst_entry *dst = __sk_dst_get(sk); + + if (dst && dst_feature(dst, RTAX_FEATURE_ECN)) + use_ecn = true; + } + + tp->ecn_flags = 0; + + if (use_ecn) { + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR; + tp->ecn_flags = TCP_ECN_OK; + if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn) + INET_ECN_xmit(sk); + } +} + +static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb) +{ + if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)) + /* tp->ecn_flags are cleared at a later point in time when + * SYN ACK is ultimatively being received. + */ + TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR); +} + +static void +tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th) +{ + if (inet_rsk(req)->ecn_ok) + th->ece = 1; +} + +/* Set up ECN state for a packet on a ESTABLISHED socket that is about to + * be sent. + */ +static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb, + struct tcphdr *th, int tcp_header_len) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (tp->ecn_flags & TCP_ECN_OK) { + /* Not-retransmitted data segment: set ECT and inject CWR. */ + if (skb->len != tcp_header_len && + !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) { + INET_ECN_xmit(sk); + if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) { + tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; + th->cwr = 1; + skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; + } + } else if (!tcp_ca_needs_ecn(sk)) { + /* ACK or retransmitted segment: clear ECT|CE */ + INET_ECN_dontxmit(sk); + } + if (tp->ecn_flags & TCP_ECN_DEMAND_CWR) + th->ece = 1; + } +} + +/* Constructs common control bits of non-data skb. If SYN/FIN is present, + * auto increment end seqno. + */ +static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags) +{ + skb->ip_summed = CHECKSUM_PARTIAL; + + TCP_SKB_CB(skb)->tcp_flags = flags; + + tcp_skb_pcount_set(skb, 1); + + TCP_SKB_CB(skb)->seq = seq; + if (flags & (TCPHDR_SYN | TCPHDR_FIN)) + seq++; + TCP_SKB_CB(skb)->end_seq = seq; +} + +static inline bool tcp_urg_mode(const struct tcp_sock *tp) +{ + return tp->snd_una != tp->snd_up; +} + +#define OPTION_SACK_ADVERTISE BIT(0) +#define OPTION_TS BIT(1) +#define OPTION_MD5 BIT(2) +#define OPTION_WSCALE BIT(3) +#define OPTION_FAST_OPEN_COOKIE BIT(8) +#define OPTION_SMC BIT(9) +#define OPTION_MPTCP BIT(10) + +static void smc_options_write(__be32 *ptr, u16 *options) +{ +#if IS_ENABLED(CONFIG_SMC) + if (static_branch_unlikely(&tcp_have_smc)) { + if (unlikely(OPTION_SMC & *options)) { + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_NOP << 16) | + (TCPOPT_EXP << 8) | + (TCPOLEN_EXP_SMC_BASE)); + *ptr++ = htonl(TCPOPT_SMC_MAGIC); + } + } +#endif +} + +struct tcp_out_options { + u16 options; /* bit field of OPTION_* */ + u16 mss; /* 0 to disable */ + u8 ws; /* window scale, 0 to disable */ + u8 num_sack_blocks; /* number of SACK blocks to include */ + u8 hash_size; /* bytes in hash_location */ + u8 bpf_opt_len; /* length of BPF hdr option */ + __u8 *hash_location; /* temporary pointer, overloaded */ + __u32 tsval, tsecr; /* need to include OPTION_TS */ + struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */ + struct mptcp_out_options mptcp; +}; + +static void mptcp_options_write(struct tcphdr *th, __be32 *ptr, + struct tcp_sock *tp, + struct tcp_out_options *opts) +{ +#if IS_ENABLED(CONFIG_MPTCP) + if (unlikely(OPTION_MPTCP & opts->options)) + mptcp_write_options(th, ptr, tp, &opts->mptcp); +#endif +} + +#ifdef CONFIG_CGROUP_BPF +static int bpf_skops_write_hdr_opt_arg0(struct sk_buff *skb, + enum tcp_synack_type synack_type) +{ + if (unlikely(!skb)) + return BPF_WRITE_HDR_TCP_CURRENT_MSS; + + if (unlikely(synack_type == TCP_SYNACK_COOKIE)) + return BPF_WRITE_HDR_TCP_SYNACK_COOKIE; + + return 0; +} + +/* req, syn_skb and synack_type are used when writing synack */ +static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb, + struct request_sock *req, + struct sk_buff *syn_skb, + enum tcp_synack_type synack_type, + struct tcp_out_options *opts, + unsigned int *remaining) +{ + struct bpf_sock_ops_kern sock_ops; + int err; + + if (likely(!BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), + BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG)) || + !*remaining) + return; + + /* *remaining has already been aligned to 4 bytes, so *remaining >= 4 */ + + /* init sock_ops */ + memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp)); + + sock_ops.op = BPF_SOCK_OPS_HDR_OPT_LEN_CB; + + if (req) { + /* The listen "sk" cannot be passed here because + * it is not locked. It would not make too much + * sense to do bpf_setsockopt(listen_sk) based + * on individual connection request also. + * + * Thus, "req" is passed here and the cgroup-bpf-progs + * of the listen "sk" will be run. + * + * "req" is also used here for fastopen even the "sk" here is + * a fullsock "child" sk. It is to keep the behavior + * consistent between fastopen and non-fastopen on + * the bpf programming side. + */ + sock_ops.sk = (struct sock *)req; + sock_ops.syn_skb = syn_skb; + } else { + sock_owned_by_me(sk); + + sock_ops.is_fullsock = 1; + sock_ops.sk = sk; + } + + sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type); + sock_ops.remaining_opt_len = *remaining; + /* tcp_current_mss() does not pass a skb */ + if (skb) + bpf_skops_init_skb(&sock_ops, skb, 0); + + err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk); + + if (err || sock_ops.remaining_opt_len == *remaining) + return; + + opts->bpf_opt_len = *remaining - sock_ops.remaining_opt_len; + /* round up to 4 bytes */ + opts->bpf_opt_len = (opts->bpf_opt_len + 3) & ~3; + + *remaining -= opts->bpf_opt_len; +} + +static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb, + struct request_sock *req, + struct sk_buff *syn_skb, + enum tcp_synack_type synack_type, + struct tcp_out_options *opts) +{ + u8 first_opt_off, nr_written, max_opt_len = opts->bpf_opt_len; + struct bpf_sock_ops_kern sock_ops; + int err; + + if (likely(!max_opt_len)) + return; + + memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp)); + + sock_ops.op = BPF_SOCK_OPS_WRITE_HDR_OPT_CB; + + if (req) { + sock_ops.sk = (struct sock *)req; + sock_ops.syn_skb = syn_skb; + } else { + sock_owned_by_me(sk); + + sock_ops.is_fullsock = 1; + sock_ops.sk = sk; + } + + sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type); + sock_ops.remaining_opt_len = max_opt_len; + first_opt_off = tcp_hdrlen(skb) - max_opt_len; + bpf_skops_init_skb(&sock_ops, skb, first_opt_off); + + err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk); + + if (err) + nr_written = 0; + else + nr_written = max_opt_len - sock_ops.remaining_opt_len; + + if (nr_written < max_opt_len) + memset(skb->data + first_opt_off + nr_written, TCPOPT_NOP, + max_opt_len - nr_written); +} +#else +static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb, + struct request_sock *req, + struct sk_buff *syn_skb, + enum tcp_synack_type synack_type, + struct tcp_out_options *opts, + unsigned int *remaining) +{ +} + +static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb, + struct request_sock *req, + struct sk_buff *syn_skb, + enum tcp_synack_type synack_type, + struct tcp_out_options *opts) +{ +} +#endif + +/* Write previously computed TCP options to the packet. + * + * Beware: Something in the Internet is very sensitive to the ordering of + * TCP options, we learned this through the hard way, so be careful here. + * Luckily we can at least blame others for their non-compliance but from + * inter-operability perspective it seems that we're somewhat stuck with + * the ordering which we have been using if we want to keep working with + * those broken things (not that it currently hurts anybody as there isn't + * particular reason why the ordering would need to be changed). + * + * At least SACK_PERM as the first option is known to lead to a disaster + * (but it may well be that other scenarios fail similarly). + */ +static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, + struct tcp_out_options *opts) +{ + __be32 *ptr = (__be32 *)(th + 1); + u16 options = opts->options; /* mungable copy */ + + if (unlikely(OPTION_MD5 & options)) { + *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | + (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG); + /* overload cookie hash location */ + opts->hash_location = (__u8 *)ptr; + ptr += 4; + } + + if (unlikely(opts->mss)) { + *ptr++ = htonl((TCPOPT_MSS << 24) | + (TCPOLEN_MSS << 16) | + opts->mss); + } + + if (likely(OPTION_TS & options)) { + if (unlikely(OPTION_SACK_ADVERTISE & options)) { + *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | + (TCPOLEN_SACK_PERM << 16) | + (TCPOPT_TIMESTAMP << 8) | + TCPOLEN_TIMESTAMP); + options &= ~OPTION_SACK_ADVERTISE; + } else { + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_NOP << 16) | + (TCPOPT_TIMESTAMP << 8) | + TCPOLEN_TIMESTAMP); + } + *ptr++ = htonl(opts->tsval); + *ptr++ = htonl(opts->tsecr); + } + + if (unlikely(OPTION_SACK_ADVERTISE & options)) { + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_NOP << 16) | + (TCPOPT_SACK_PERM << 8) | + TCPOLEN_SACK_PERM); + } + + if (unlikely(OPTION_WSCALE & options)) { + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_WINDOW << 16) | + (TCPOLEN_WINDOW << 8) | + opts->ws); + } + + if (unlikely(opts->num_sack_blocks)) { + struct tcp_sack_block *sp = tp->rx_opt.dsack ? + tp->duplicate_sack : tp->selective_acks; + int this_sack; + + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_NOP << 16) | + (TCPOPT_SACK << 8) | + (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * + TCPOLEN_SACK_PERBLOCK))); + + for (this_sack = 0; this_sack < opts->num_sack_blocks; + ++this_sack) { + *ptr++ = htonl(sp[this_sack].start_seq); + *ptr++ = htonl(sp[this_sack].end_seq); + } + + tp->rx_opt.dsack = 0; + } + + if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) { + struct tcp_fastopen_cookie *foc = opts->fastopen_cookie; + u8 *p = (u8 *)ptr; + u32 len; /* Fast Open option length */ + + if (foc->exp) { + len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len; + *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) | + TCPOPT_FASTOPEN_MAGIC); + p += TCPOLEN_EXP_FASTOPEN_BASE; + } else { + len = TCPOLEN_FASTOPEN_BASE + foc->len; + *p++ = TCPOPT_FASTOPEN; + *p++ = len; + } + + memcpy(p, foc->val, foc->len); + if ((len & 3) == 2) { + p[foc->len] = TCPOPT_NOP; + p[foc->len + 1] = TCPOPT_NOP; + } + ptr += (len + 3) >> 2; + } + + smc_options_write(ptr, &options); + + mptcp_options_write(th, ptr, tp, opts); +} + +static void smc_set_option(const struct tcp_sock *tp, + struct tcp_out_options *opts, + unsigned int *remaining) +{ +#if IS_ENABLED(CONFIG_SMC) + if (static_branch_unlikely(&tcp_have_smc)) { + if (tp->syn_smc) { + if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) { + opts->options |= OPTION_SMC; + *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED; + } + } + } +#endif +} + +static void smc_set_option_cond(const struct tcp_sock *tp, + const struct inet_request_sock *ireq, + struct tcp_out_options *opts, + unsigned int *remaining) +{ +#if IS_ENABLED(CONFIG_SMC) + if (static_branch_unlikely(&tcp_have_smc)) { + if (tp->syn_smc && ireq->smc_ok) { + if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) { + opts->options |= OPTION_SMC; + *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED; + } + } + } +#endif +} + +static void mptcp_set_option_cond(const struct request_sock *req, + struct tcp_out_options *opts, + unsigned int *remaining) +{ + if (rsk_is_mptcp(req)) { + unsigned int size; + + if (mptcp_synack_options(req, &size, &opts->mptcp)) { + if (*remaining >= size) { + opts->options |= OPTION_MPTCP; + *remaining -= size; + } + } + } +} + +/* Compute TCP options for SYN packets. This is not the final + * network wire format yet. + */ +static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, + struct tcp_out_options *opts, + struct tcp_md5sig_key **md5) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned int remaining = MAX_TCP_OPTION_SPACE; + struct tcp_fastopen_request *fastopen = tp->fastopen_req; + + *md5 = NULL; +#ifdef CONFIG_TCP_MD5SIG + if (static_branch_unlikely(&tcp_md5_needed) && + rcu_access_pointer(tp->md5sig_info)) { + *md5 = tp->af_specific->md5_lookup(sk, sk); + if (*md5) { + opts->options |= OPTION_MD5; + remaining -= TCPOLEN_MD5SIG_ALIGNED; + } + } +#endif + + /* We always get an MSS option. The option bytes which will be seen in + * normal data packets should timestamps be used, must be in the MSS + * advertised. But we subtract them from tp->mss_cache so that + * calculations in tcp_sendmsg are simpler etc. So account for this + * fact here if necessary. If we don't do this correctly, as a + * receiver we won't recognize data packets as being full sized when we + * should, and thus we won't abide by the delayed ACK rules correctly. + * SACKs don't matter, we never delay an ACK when we have any of those + * going out. */ + opts->mss = tcp_advertise_mss(sk); + remaining -= TCPOLEN_MSS_ALIGNED; + + if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps) && !*md5)) { + opts->options |= OPTION_TS; + opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset; + opts->tsecr = tp->rx_opt.ts_recent; + remaining -= TCPOLEN_TSTAMP_ALIGNED; + } + if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_window_scaling))) { + opts->ws = tp->rx_opt.rcv_wscale; + opts->options |= OPTION_WSCALE; + remaining -= TCPOLEN_WSCALE_ALIGNED; + } + if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_sack))) { + opts->options |= OPTION_SACK_ADVERTISE; + if (unlikely(!(OPTION_TS & opts->options))) + remaining -= TCPOLEN_SACKPERM_ALIGNED; + } + + if (fastopen && fastopen->cookie.len >= 0) { + u32 need = fastopen->cookie.len; + + need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE : + TCPOLEN_FASTOPEN_BASE; + need = (need + 3) & ~3U; /* Align to 32 bits */ + if (remaining >= need) { + opts->options |= OPTION_FAST_OPEN_COOKIE; + opts->fastopen_cookie = &fastopen->cookie; + remaining -= need; + tp->syn_fastopen = 1; + tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0; + } + } + + smc_set_option(tp, opts, &remaining); + + if (sk_is_mptcp(sk)) { + unsigned int size; + + if (mptcp_syn_options(sk, skb, &size, &opts->mptcp)) { + opts->options |= OPTION_MPTCP; + remaining -= size; + } + } + + bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining); + + return MAX_TCP_OPTION_SPACE - remaining; +} + +/* Set up TCP options for SYN-ACKs. */ +static unsigned int tcp_synack_options(const struct sock *sk, + struct request_sock *req, + unsigned int mss, struct sk_buff *skb, + struct tcp_out_options *opts, + const struct tcp_md5sig_key *md5, + struct tcp_fastopen_cookie *foc, + enum tcp_synack_type synack_type, + struct sk_buff *syn_skb) +{ + struct inet_request_sock *ireq = inet_rsk(req); + unsigned int remaining = MAX_TCP_OPTION_SPACE; + +#ifdef CONFIG_TCP_MD5SIG + if (md5) { + opts->options |= OPTION_MD5; + remaining -= TCPOLEN_MD5SIG_ALIGNED; + + /* We can't fit any SACK blocks in a packet with MD5 + TS + * options. There was discussion about disabling SACK + * rather than TS in order to fit in better with old, + * buggy kernels, but that was deemed to be unnecessary. + */ + if (synack_type != TCP_SYNACK_COOKIE) + ireq->tstamp_ok &= !ireq->sack_ok; + } +#endif + + /* We always send an MSS option. */ + opts->mss = mss; + remaining -= TCPOLEN_MSS_ALIGNED; + + if (likely(ireq->wscale_ok)) { + opts->ws = ireq->rcv_wscale; + opts->options |= OPTION_WSCALE; + remaining -= TCPOLEN_WSCALE_ALIGNED; + } + if (likely(ireq->tstamp_ok)) { + opts->options |= OPTION_TS; + opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off; + opts->tsecr = READ_ONCE(req->ts_recent); + remaining -= TCPOLEN_TSTAMP_ALIGNED; + } + if (likely(ireq->sack_ok)) { + opts->options |= OPTION_SACK_ADVERTISE; + if (unlikely(!ireq->tstamp_ok)) + remaining -= TCPOLEN_SACKPERM_ALIGNED; + } + if (foc != NULL && foc->len >= 0) { + u32 need = foc->len; + + need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE : + TCPOLEN_FASTOPEN_BASE; + need = (need + 3) & ~3U; /* Align to 32 bits */ + if (remaining >= need) { + opts->options |= OPTION_FAST_OPEN_COOKIE; + opts->fastopen_cookie = foc; + remaining -= need; + } + } + + mptcp_set_option_cond(req, opts, &remaining); + + smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining); + + bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb, + synack_type, opts, &remaining); + + return MAX_TCP_OPTION_SPACE - remaining; +} + +/* Compute TCP options for ESTABLISHED sockets. This is not the + * final wire format yet. + */ +static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb, + struct tcp_out_options *opts, + struct tcp_md5sig_key **md5) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned int size = 0; + unsigned int eff_sacks; + + opts->options = 0; + + *md5 = NULL; +#ifdef CONFIG_TCP_MD5SIG + if (static_branch_unlikely(&tcp_md5_needed) && + rcu_access_pointer(tp->md5sig_info)) { + *md5 = tp->af_specific->md5_lookup(sk, sk); + if (*md5) { + opts->options |= OPTION_MD5; + size += TCPOLEN_MD5SIG_ALIGNED; + } + } +#endif + + if (likely(tp->rx_opt.tstamp_ok)) { + opts->options |= OPTION_TS; + opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0; + opts->tsecr = tp->rx_opt.ts_recent; + size += TCPOLEN_TSTAMP_ALIGNED; + } + + /* MPTCP options have precedence over SACK for the limited TCP + * option space because a MPTCP connection would be forced to + * fall back to regular TCP if a required multipath option is + * missing. SACK still gets a chance to use whatever space is + * left. + */ + if (sk_is_mptcp(sk)) { + unsigned int remaining = MAX_TCP_OPTION_SPACE - size; + unsigned int opt_size = 0; + + if (mptcp_established_options(sk, skb, &opt_size, remaining, + &opts->mptcp)) { + opts->options |= OPTION_MPTCP; + size += opt_size; + } + } + + eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack; + if (unlikely(eff_sacks)) { + const unsigned int remaining = MAX_TCP_OPTION_SPACE - size; + if (unlikely(remaining < TCPOLEN_SACK_BASE_ALIGNED + + TCPOLEN_SACK_PERBLOCK)) + return size; + + opts->num_sack_blocks = + min_t(unsigned int, eff_sacks, + (remaining - TCPOLEN_SACK_BASE_ALIGNED) / + TCPOLEN_SACK_PERBLOCK); + + size += TCPOLEN_SACK_BASE_ALIGNED + + opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; + } + + if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp, + BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG))) { + unsigned int remaining = MAX_TCP_OPTION_SPACE - size; + + bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining); + + size = MAX_TCP_OPTION_SPACE - remaining; + } + + return size; +} + + +/* TCP SMALL QUEUES (TSQ) + * + * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev) + * to reduce RTT and bufferbloat. + * We do this using a special skb destructor (tcp_wfree). + * + * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb + * needs to be reallocated in a driver. + * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc + * + * Since transmit from skb destructor is forbidden, we use a tasklet + * to process all sockets that eventually need to send more skbs. + * We use one tasklet per cpu, with its own queue of sockets. + */ +struct tsq_tasklet { + struct tasklet_struct tasklet; + struct list_head head; /* queue of tcp sockets */ +}; +static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet); + +static void tcp_tsq_write(struct sock *sk) +{ + if ((1 << sk->sk_state) & + (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING | + TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) { + struct tcp_sock *tp = tcp_sk(sk); + + if (tp->lost_out > tp->retrans_out && + tcp_snd_cwnd(tp) > tcp_packets_in_flight(tp)) { + tcp_mstamp_refresh(tp); + tcp_xmit_retransmit_queue(sk); + } + + tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle, + 0, GFP_ATOMIC); + } +} + +static void tcp_tsq_handler(struct sock *sk) +{ + bh_lock_sock(sk); + if (!sock_owned_by_user(sk)) + tcp_tsq_write(sk); + else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags)) + sock_hold(sk); + bh_unlock_sock(sk); +} +/* + * One tasklet per cpu tries to send more skbs. + * We run in tasklet context but need to disable irqs when + * transferring tsq->head because tcp_wfree() might + * interrupt us (non NAPI drivers) + */ +static void tcp_tasklet_func(struct tasklet_struct *t) +{ + struct tsq_tasklet *tsq = from_tasklet(tsq, t, tasklet); + LIST_HEAD(list); + unsigned long flags; + struct list_head *q, *n; + struct tcp_sock *tp; + struct sock *sk; + + local_irq_save(flags); + list_splice_init(&tsq->head, &list); + local_irq_restore(flags); + + list_for_each_safe(q, n, &list) { + tp = list_entry(q, struct tcp_sock, tsq_node); + list_del(&tp->tsq_node); + + sk = (struct sock *)tp; + smp_mb__before_atomic(); + clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags); + + tcp_tsq_handler(sk); + sk_free(sk); + } +} + +#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \ + TCPF_WRITE_TIMER_DEFERRED | \ + TCPF_DELACK_TIMER_DEFERRED | \ + TCPF_MTU_REDUCED_DEFERRED) +/** + * tcp_release_cb - tcp release_sock() callback + * @sk: socket + * + * called from release_sock() to perform protocol dependent + * actions before socket release. + */ +void tcp_release_cb(struct sock *sk) +{ + unsigned long flags, nflags; + + /* perform an atomic operation only if at least one flag is set */ + do { + flags = sk->sk_tsq_flags; + if (!(flags & TCP_DEFERRED_ALL)) + return; + nflags = flags & ~TCP_DEFERRED_ALL; + } while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags); + + if (flags & TCPF_TSQ_DEFERRED) { + tcp_tsq_write(sk); + __sock_put(sk); + } + /* Here begins the tricky part : + * We are called from release_sock() with : + * 1) BH disabled + * 2) sk_lock.slock spinlock held + * 3) socket owned by us (sk->sk_lock.owned == 1) + * + * But following code is meant to be called from BH handlers, + * so we should keep BH disabled, but early release socket ownership + */ + sock_release_ownership(sk); + + if (flags & TCPF_WRITE_TIMER_DEFERRED) { + tcp_write_timer_handler(sk); + __sock_put(sk); + } + if (flags & TCPF_DELACK_TIMER_DEFERRED) { + tcp_delack_timer_handler(sk); + __sock_put(sk); + } + if (flags & TCPF_MTU_REDUCED_DEFERRED) { + inet_csk(sk)->icsk_af_ops->mtu_reduced(sk); + __sock_put(sk); + } +} +EXPORT_SYMBOL(tcp_release_cb); + +void __init tcp_tasklet_init(void) +{ + int i; + + for_each_possible_cpu(i) { + struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i); + + INIT_LIST_HEAD(&tsq->head); + tasklet_setup(&tsq->tasklet, tcp_tasklet_func); + } +} + +/* + * Write buffer destructor automatically called from kfree_skb. + * We can't xmit new skbs from this context, as we might already + * hold qdisc lock. + */ +void tcp_wfree(struct sk_buff *skb) +{ + struct sock *sk = skb->sk; + struct tcp_sock *tp = tcp_sk(sk); + unsigned long flags, nval, oval; + + /* Keep one reference on sk_wmem_alloc. + * Will be released by sk_free() from here or tcp_tasklet_func() + */ + WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc)); + + /* If this softirq is serviced by ksoftirqd, we are likely under stress. + * Wait until our queues (qdisc + devices) are drained. + * This gives : + * - less callbacks to tcp_write_xmit(), reducing stress (batches) + * - chance for incoming ACK (processed by another cpu maybe) + * to migrate this flow (skb->ooo_okay will be eventually set) + */ + if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current) + goto out; + + for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) { + struct tsq_tasklet *tsq; + bool empty; + + if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED)) + goto out; + + nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED; + nval = cmpxchg(&sk->sk_tsq_flags, oval, nval); + if (nval != oval) + continue; + + /* queue this socket to tasklet queue */ + local_irq_save(flags); + tsq = this_cpu_ptr(&tsq_tasklet); + empty = list_empty(&tsq->head); + list_add(&tp->tsq_node, &tsq->head); + if (empty) + tasklet_schedule(&tsq->tasklet); + local_irq_restore(flags); + return; + } +out: + sk_free(sk); +} + +/* Note: Called under soft irq. + * We can call TCP stack right away, unless socket is owned by user. + */ +enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer) +{ + struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer); + struct sock *sk = (struct sock *)tp; + + tcp_tsq_handler(sk); + sock_put(sk); + + return HRTIMER_NORESTART; +} + +static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb, + u64 prior_wstamp) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (sk->sk_pacing_status != SK_PACING_NONE) { + unsigned long rate = sk->sk_pacing_rate; + + /* Original sch_fq does not pace first 10 MSS + * Note that tp->data_segs_out overflows after 2^32 packets, + * this is a minor annoyance. + */ + if (rate != ~0UL && rate && tp->data_segs_out >= 10) { + u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate); + u64 credit = tp->tcp_wstamp_ns - prior_wstamp; + + /* take into account OS jitter */ + len_ns -= min_t(u64, len_ns / 2, credit); + tp->tcp_wstamp_ns += len_ns; + } + } + list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue); +} + +INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)); +INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)); +INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb)); + +/* This routine actually transmits TCP packets queued in by + * tcp_do_sendmsg(). This is used by both the initial + * transmission and possible later retransmissions. + * All SKB's seen here are completely headerless. It is our + * job to build the TCP header, and pass the packet down to + * IP so it can do the same plus pass the packet off to the + * device. + * + * We are working here with either a clone of the original + * SKB, or a fresh unique copy made by the retransmit engine. + */ +static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, + int clone_it, gfp_t gfp_mask, u32 rcv_nxt) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + struct inet_sock *inet; + struct tcp_sock *tp; + struct tcp_skb_cb *tcb; + struct tcp_out_options opts; + unsigned int tcp_options_size, tcp_header_size; + struct sk_buff *oskb = NULL; + struct tcp_md5sig_key *md5; + struct tcphdr *th; + u64 prior_wstamp; + int err; + + BUG_ON(!skb || !tcp_skb_pcount(skb)); + tp = tcp_sk(sk); + prior_wstamp = tp->tcp_wstamp_ns; + tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache); + skb_set_delivery_time(skb, tp->tcp_wstamp_ns, true); + if (clone_it) { + oskb = skb; + + tcp_skb_tsorted_save(oskb) { + if (unlikely(skb_cloned(oskb))) + skb = pskb_copy(oskb, gfp_mask); + else + skb = skb_clone(oskb, gfp_mask); + } tcp_skb_tsorted_restore(oskb); + + if (unlikely(!skb)) + return -ENOBUFS; + /* retransmit skbs might have a non zero value in skb->dev + * because skb->dev is aliased with skb->rbnode.rb_left + */ + skb->dev = NULL; + } + + inet = inet_sk(sk); + tcb = TCP_SKB_CB(skb); + memset(&opts, 0, sizeof(opts)); + + if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) { + tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); + } else { + tcp_options_size = tcp_established_options(sk, skb, &opts, + &md5); + /* Force a PSH flag on all (GSO) packets to expedite GRO flush + * at receiver : This slightly improve GRO performance. + * Note that we do not force the PSH flag for non GSO packets, + * because they might be sent under high congestion events, + * and in this case it is better to delay the delivery of 1-MSS + * packets and thus the corresponding ACK packet that would + * release the following packet. + */ + if (tcp_skb_pcount(skb) > 1) + tcb->tcp_flags |= TCPHDR_PSH; + } + tcp_header_size = tcp_options_size + sizeof(struct tcphdr); + + /* if no packet is in qdisc/device queue, then allow XPS to select + * another queue. We can be called from tcp_tsq_handler() + * which holds one reference to sk. + * + * TODO: Ideally, in-flight pure ACK packets should not matter here. + * One way to get this would be to set skb->truesize = 2 on them. + */ + skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1); + + /* If we had to use memory reserve to allocate this skb, + * this might cause drops if packet is looped back : + * Other socket might not have SOCK_MEMALLOC. + * Packets not looped back do not care about pfmemalloc. + */ + skb->pfmemalloc = 0; + + skb_push(skb, tcp_header_size); + skb_reset_transport_header(skb); + + skb_orphan(skb); + skb->sk = sk; + skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree; + refcount_add(skb->truesize, &sk->sk_wmem_alloc); + + skb_set_dst_pending_confirm(skb, READ_ONCE(sk->sk_dst_pending_confirm)); + + /* Build TCP header and checksum it. */ + th = (struct tcphdr *)skb->data; + th->source = inet->inet_sport; + th->dest = inet->inet_dport; + th->seq = htonl(tcb->seq); + th->ack_seq = htonl(rcv_nxt); + *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | + tcb->tcp_flags); + + th->check = 0; + th->urg_ptr = 0; + + /* The urg_mode check is necessary during a below snd_una win probe */ + if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) { + if (before(tp->snd_up, tcb->seq + 0x10000)) { + th->urg_ptr = htons(tp->snd_up - tcb->seq); + th->urg = 1; + } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) { + th->urg_ptr = htons(0xFFFF); + th->urg = 1; + } + } + + skb_shinfo(skb)->gso_type = sk->sk_gso_type; + if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) { + th->window = htons(tcp_select_window(sk)); + tcp_ecn_send(sk, skb, th, tcp_header_size); + } else { + /* RFC1323: The window in SYN & SYN/ACK segments + * is never scaled. + */ + th->window = htons(min(tp->rcv_wnd, 65535U)); + } + + tcp_options_write(th, tp, &opts); + +#ifdef CONFIG_TCP_MD5SIG + /* Calculate the MD5 hash, as we have all we need now */ + if (md5) { + sk_gso_disable(sk); + tp->af_specific->calc_md5_hash(opts.hash_location, + md5, sk, skb); + } +#endif + + /* BPF prog is the last one writing header option */ + bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts); + + INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check, + tcp_v6_send_check, tcp_v4_send_check, + sk, skb); + + if (likely(tcb->tcp_flags & TCPHDR_ACK)) + tcp_event_ack_sent(sk, rcv_nxt); + + if (skb->len != tcp_header_size) { + tcp_event_data_sent(tp, sk); + tp->data_segs_out += tcp_skb_pcount(skb); + tp->bytes_sent += skb->len - tcp_header_size; + } + + if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq) + TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, + tcp_skb_pcount(skb)); + + tp->segs_out += tcp_skb_pcount(skb); + skb_set_hash_from_sk(skb, sk); + /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */ + skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb); + skb_shinfo(skb)->gso_size = tcp_skb_mss(skb); + + /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */ + + /* Cleanup our debris for IP stacks */ + memset(skb->cb, 0, max(sizeof(struct inet_skb_parm), + sizeof(struct inet6_skb_parm))); + + tcp_add_tx_delay(skb, tp); + + err = INDIRECT_CALL_INET(icsk->icsk_af_ops->queue_xmit, + inet6_csk_xmit, ip_queue_xmit, + sk, skb, &inet->cork.fl); + + if (unlikely(err > 0)) { + tcp_enter_cwr(sk); + err = net_xmit_eval(err); + } + if (!err && oskb) { + tcp_update_skb_after_send(sk, oskb, prior_wstamp); + tcp_rate_skb_sent(sk, oskb); + } + return err; +} + +static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, + gfp_t gfp_mask) +{ + return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask, + tcp_sk(sk)->rcv_nxt); +} + +/* This routine just queues the buffer for sending. + * + * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, + * otherwise socket can stall. + */ +static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* Advance write_seq and place onto the write_queue. */ + WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq); + __skb_header_release(skb); + tcp_add_write_queue_tail(sk, skb); + sk_wmem_queued_add(sk, skb->truesize); + sk_mem_charge(sk, skb->truesize); +} + +/* Initialize TSO segments for a packet. */ +static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now) +{ + if (skb->len <= mss_now) { + /* Avoid the costly divide in the normal + * non-TSO case. + */ + tcp_skb_pcount_set(skb, 1); + TCP_SKB_CB(skb)->tcp_gso_size = 0; + } else { + tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now)); + TCP_SKB_CB(skb)->tcp_gso_size = mss_now; + } +} + +/* Pcount in the middle of the write queue got changed, we need to do various + * tweaks to fix counters + */ +static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tp->packets_out -= decr; + + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) + tp->sacked_out -= decr; + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) + tp->retrans_out -= decr; + if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) + tp->lost_out -= decr; + + /* Reno case is special. Sigh... */ + if (tcp_is_reno(tp) && decr > 0) + tp->sacked_out -= min_t(u32, tp->sacked_out, decr); + + if (tp->lost_skb_hint && + before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) && + (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) + tp->lost_cnt_hint -= decr; + + tcp_verify_left_out(tp); +} + +static bool tcp_has_tx_tstamp(const struct sk_buff *skb) +{ + return TCP_SKB_CB(skb)->txstamp_ack || + (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP); +} + +static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2) +{ + struct skb_shared_info *shinfo = skb_shinfo(skb); + + if (unlikely(tcp_has_tx_tstamp(skb)) && + !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) { + struct skb_shared_info *shinfo2 = skb_shinfo(skb2); + u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP; + + shinfo->tx_flags &= ~tsflags; + shinfo2->tx_flags |= tsflags; + swap(shinfo->tskey, shinfo2->tskey); + TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack; + TCP_SKB_CB(skb)->txstamp_ack = 0; + } +} + +static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2) +{ + TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor; + TCP_SKB_CB(skb)->eor = 0; +} + +/* Insert buff after skb on the write or rtx queue of sk. */ +static void tcp_insert_write_queue_after(struct sk_buff *skb, + struct sk_buff *buff, + struct sock *sk, + enum tcp_queue tcp_queue) +{ + if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE) + __skb_queue_after(&sk->sk_write_queue, skb, buff); + else + tcp_rbtree_insert(&sk->tcp_rtx_queue, buff); +} + +/* Function to create two new TCP segments. Shrinks the given segment + * to the specified size and appends a new segment with the rest of the + * packet to the list. This won't be called frequently, I hope. + * Remember, these are still headerless SKBs at this point. + */ +int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue, + struct sk_buff *skb, u32 len, + unsigned int mss_now, gfp_t gfp) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *buff; + int nsize, old_factor; + long limit; + int nlen; + u8 flags; + + if (WARN_ON(len > skb->len)) + return -EINVAL; + + nsize = skb_headlen(skb) - len; + if (nsize < 0) + nsize = 0; + + /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb. + * We need some allowance to not penalize applications setting small + * SO_SNDBUF values. + * Also allow first and last skb in retransmit queue to be split. + */ + limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_LEGACY_MAX_SIZE); + if (unlikely((sk->sk_wmem_queued >> 1) > limit && + tcp_queue != TCP_FRAG_IN_WRITE_QUEUE && + skb != tcp_rtx_queue_head(sk) && + skb != tcp_rtx_queue_tail(sk))) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG); + return -ENOMEM; + } + + if (skb_unclone_keeptruesize(skb, gfp)) + return -ENOMEM; + + /* Get a new skb... force flag on. */ + buff = tcp_stream_alloc_skb(sk, nsize, gfp, true); + if (!buff) + return -ENOMEM; /* We'll just try again later. */ + skb_copy_decrypted(buff, skb); + mptcp_skb_ext_copy(buff, skb); + + sk_wmem_queued_add(sk, buff->truesize); + sk_mem_charge(sk, buff->truesize); + nlen = skb->len - len - nsize; + buff->truesize += nlen; + skb->truesize -= nlen; + + /* Correct the sequence numbers. */ + TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; + TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; + + /* PSH and FIN should only be set in the second packet. */ + flags = TCP_SKB_CB(skb)->tcp_flags; + TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH); + TCP_SKB_CB(buff)->tcp_flags = flags; + TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked; + tcp_skb_fragment_eor(skb, buff); + + skb_split(skb, buff, len); + + skb_set_delivery_time(buff, skb->tstamp, true); + tcp_fragment_tstamp(skb, buff); + + old_factor = tcp_skb_pcount(skb); + + /* Fix up tso_factor for both original and new SKB. */ + tcp_set_skb_tso_segs(skb, mss_now); + tcp_set_skb_tso_segs(buff, mss_now); + + /* Update delivered info for the new segment */ + TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx; + + /* If this packet has been sent out already, we must + * adjust the various packet counters. + */ + if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) { + int diff = old_factor - tcp_skb_pcount(skb) - + tcp_skb_pcount(buff); + + if (diff) + tcp_adjust_pcount(sk, skb, diff); + } + + /* Link BUFF into the send queue. */ + __skb_header_release(buff); + tcp_insert_write_queue_after(skb, buff, sk, tcp_queue); + if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE) + list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor); + + return 0; +} + +/* This is similar to __pskb_pull_tail(). The difference is that pulled + * data is not copied, but immediately discarded. + */ +static int __pskb_trim_head(struct sk_buff *skb, int len) +{ + struct skb_shared_info *shinfo; + int i, k, eat; + + eat = min_t(int, len, skb_headlen(skb)); + if (eat) { + __skb_pull(skb, eat); + len -= eat; + if (!len) + return 0; + } + eat = len; + k = 0; + shinfo = skb_shinfo(skb); + for (i = 0; i < shinfo->nr_frags; i++) { + int size = skb_frag_size(&shinfo->frags[i]); + + if (size <= eat) { + skb_frag_unref(skb, i); + eat -= size; + } else { + shinfo->frags[k] = shinfo->frags[i]; + if (eat) { + skb_frag_off_add(&shinfo->frags[k], eat); + skb_frag_size_sub(&shinfo->frags[k], eat); + eat = 0; + } + k++; + } + } + shinfo->nr_frags = k; + + skb->data_len -= len; + skb->len = skb->data_len; + return len; +} + +/* Remove acked data from a packet in the transmit queue. */ +int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) +{ + u32 delta_truesize; + + if (skb_unclone_keeptruesize(skb, GFP_ATOMIC)) + return -ENOMEM; + + delta_truesize = __pskb_trim_head(skb, len); + + TCP_SKB_CB(skb)->seq += len; + + if (delta_truesize) { + skb->truesize -= delta_truesize; + sk_wmem_queued_add(sk, -delta_truesize); + if (!skb_zcopy_pure(skb)) + sk_mem_uncharge(sk, delta_truesize); + } + + /* Any change of skb->len requires recalculation of tso factor. */ + if (tcp_skb_pcount(skb) > 1) + tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb)); + + return 0; +} + +/* Calculate MSS not accounting any TCP options. */ +static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu) +{ + const struct tcp_sock *tp = tcp_sk(sk); + const struct inet_connection_sock *icsk = inet_csk(sk); + int mss_now; + + /* Calculate base mss without TCP options: + It is MMS_S - sizeof(tcphdr) of rfc1122 + */ + mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr); + + /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */ + if (icsk->icsk_af_ops->net_frag_header_len) { + const struct dst_entry *dst = __sk_dst_get(sk); + + if (dst && dst_allfrag(dst)) + mss_now -= icsk->icsk_af_ops->net_frag_header_len; + } + + /* Clamp it (mss_clamp does not include tcp options) */ + if (mss_now > tp->rx_opt.mss_clamp) + mss_now = tp->rx_opt.mss_clamp; + + /* Now subtract optional transport overhead */ + mss_now -= icsk->icsk_ext_hdr_len; + + /* Then reserve room for full set of TCP options and 8 bytes of data */ + mss_now = max(mss_now, + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss)); + return mss_now; +} + +/* Calculate MSS. Not accounting for SACKs here. */ +int tcp_mtu_to_mss(struct sock *sk, int pmtu) +{ + /* Subtract TCP options size, not including SACKs */ + return __tcp_mtu_to_mss(sk, pmtu) - + (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr)); +} +EXPORT_SYMBOL(tcp_mtu_to_mss); + +/* Inverse of above */ +int tcp_mss_to_mtu(struct sock *sk, int mss) +{ + const struct tcp_sock *tp = tcp_sk(sk); + const struct inet_connection_sock *icsk = inet_csk(sk); + int mtu; + + mtu = mss + + tp->tcp_header_len + + icsk->icsk_ext_hdr_len + + icsk->icsk_af_ops->net_header_len; + + /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */ + if (icsk->icsk_af_ops->net_frag_header_len) { + const struct dst_entry *dst = __sk_dst_get(sk); + + if (dst && dst_allfrag(dst)) + mtu += icsk->icsk_af_ops->net_frag_header_len; + } + return mtu; +} +EXPORT_SYMBOL(tcp_mss_to_mtu); + +/* MTU probing init per socket */ +void tcp_mtup_init(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + struct net *net = sock_net(sk); + + icsk->icsk_mtup.enabled = READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing) > 1; + icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) + + icsk->icsk_af_ops->net_header_len; + icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, READ_ONCE(net->ipv4.sysctl_tcp_base_mss)); + icsk->icsk_mtup.probe_size = 0; + if (icsk->icsk_mtup.enabled) + icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; +} +EXPORT_SYMBOL(tcp_mtup_init); + +/* This function synchronize snd mss to current pmtu/exthdr set. + + tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts + for TCP options, but includes only bare TCP header. + + tp->rx_opt.mss_clamp is mss negotiated at connection setup. + It is minimum of user_mss and mss received with SYN. + It also does not include TCP options. + + inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function. + + tp->mss_cache is current effective sending mss, including + all tcp options except for SACKs. It is evaluated, + taking into account current pmtu, but never exceeds + tp->rx_opt.mss_clamp. + + NOTE1. rfc1122 clearly states that advertised MSS + DOES NOT include either tcp or ip options. + + NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache + are READ ONLY outside this function. --ANK (980731) + */ +unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + int mss_now; + + if (icsk->icsk_mtup.search_high > pmtu) + icsk->icsk_mtup.search_high = pmtu; + + mss_now = tcp_mtu_to_mss(sk, pmtu); + mss_now = tcp_bound_to_half_wnd(tp, mss_now); + + /* And store cached results */ + icsk->icsk_pmtu_cookie = pmtu; + if (icsk->icsk_mtup.enabled) + mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)); + tp->mss_cache = mss_now; + + return mss_now; +} +EXPORT_SYMBOL(tcp_sync_mss); + +/* Compute the current effective MSS, taking SACKs and IP options, + * and even PMTU discovery events into account. + */ +unsigned int tcp_current_mss(struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + const struct dst_entry *dst = __sk_dst_get(sk); + u32 mss_now; + unsigned int header_len; + struct tcp_out_options opts; + struct tcp_md5sig_key *md5; + + mss_now = tp->mss_cache; + + if (dst) { + u32 mtu = dst_mtu(dst); + if (mtu != inet_csk(sk)->icsk_pmtu_cookie) + mss_now = tcp_sync_mss(sk, mtu); + } + + header_len = tcp_established_options(sk, NULL, &opts, &md5) + + sizeof(struct tcphdr); + /* The mss_cache is sized based on tp->tcp_header_len, which assumes + * some common options. If this is an odd packet (because we have SACK + * blocks etc) then our calculated header_len will be different, and + * we have to adjust mss_now correspondingly */ + if (header_len != tp->tcp_header_len) { + int delta = (int) header_len - tp->tcp_header_len; + mss_now -= delta; + } + + return mss_now; +} + +/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. + * As additional protections, we do not touch cwnd in retransmission phases, + * and if application hit its sndbuf limit recently. + */ +static void tcp_cwnd_application_limited(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && + sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { + /* Limited by application or receiver window. */ + u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); + u32 win_used = max(tp->snd_cwnd_used, init_win); + if (win_used < tcp_snd_cwnd(tp)) { + tp->snd_ssthresh = tcp_current_ssthresh(sk); + tcp_snd_cwnd_set(tp, (tcp_snd_cwnd(tp) + win_used) >> 1); + } + tp->snd_cwnd_used = 0; + } + tp->snd_cwnd_stamp = tcp_jiffies32; +} + +static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited) +{ + const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; + struct tcp_sock *tp = tcp_sk(sk); + + /* Track the strongest available signal of the degree to which the cwnd + * is fully utilized. If cwnd-limited then remember that fact for the + * current window. If not cwnd-limited then track the maximum number of + * outstanding packets in the current window. (If cwnd-limited then we + * chose to not update tp->max_packets_out to avoid an extra else + * clause with no functional impact.) + */ + if (!before(tp->snd_una, tp->cwnd_usage_seq) || + is_cwnd_limited || + (!tp->is_cwnd_limited && + tp->packets_out > tp->max_packets_out)) { + tp->is_cwnd_limited = is_cwnd_limited; + tp->max_packets_out = tp->packets_out; + tp->cwnd_usage_seq = tp->snd_nxt; + } + + if (tcp_is_cwnd_limited(sk)) { + /* Network is feed fully. */ + tp->snd_cwnd_used = 0; + tp->snd_cwnd_stamp = tcp_jiffies32; + } else { + /* Network starves. */ + if (tp->packets_out > tp->snd_cwnd_used) + tp->snd_cwnd_used = tp->packets_out; + + if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle) && + (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto && + !ca_ops->cong_control) + tcp_cwnd_application_limited(sk); + + /* The following conditions together indicate the starvation + * is caused by insufficient sender buffer: + * 1) just sent some data (see tcp_write_xmit) + * 2) not cwnd limited (this else condition) + * 3) no more data to send (tcp_write_queue_empty()) + * 4) application is hitting buffer limit (SOCK_NOSPACE) + */ + if (tcp_write_queue_empty(sk) && sk->sk_socket && + test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) && + (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) + tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED); + } +} + +/* Minshall's variant of the Nagle send check. */ +static bool tcp_minshall_check(const struct tcp_sock *tp) +{ + return after(tp->snd_sml, tp->snd_una) && + !after(tp->snd_sml, tp->snd_nxt); +} + +/* Update snd_sml if this skb is under mss + * Note that a TSO packet might end with a sub-mss segment + * The test is really : + * if ((skb->len % mss) != 0) + * tp->snd_sml = TCP_SKB_CB(skb)->end_seq; + * But we can avoid doing the divide again given we already have + * skb_pcount = skb->len / mss_now + */ +static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now, + const struct sk_buff *skb) +{ + if (skb->len < tcp_skb_pcount(skb) * mss_now) + tp->snd_sml = TCP_SKB_CB(skb)->end_seq; +} + +/* Return false, if packet can be sent now without violation Nagle's rules: + * 1. It is full sized. (provided by caller in %partial bool) + * 2. Or it contains FIN. (already checked by caller) + * 3. Or TCP_CORK is not set, and TCP_NODELAY is set. + * 4. Or TCP_CORK is not set, and all sent packets are ACKed. + * With Minshall's modification: all sent small packets are ACKed. + */ +static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp, + int nonagle) +{ + return partial && + ((nonagle & TCP_NAGLE_CORK) || + (!nonagle && tp->packets_out && tcp_minshall_check(tp))); +} + +/* Return how many segs we'd like on a TSO packet, + * depending on current pacing rate, and how close the peer is. + * + * Rationale is: + * - For close peers, we rather send bigger packets to reduce + * cpu costs, because occasional losses will be repaired fast. + * - For long distance/rtt flows, we would like to get ACK clocking + * with 1 ACK per ms. + * + * Use min_rtt to help adapt TSO burst size, with smaller min_rtt resulting + * in bigger TSO bursts. We we cut the RTT-based allowance in half + * for every 2^9 usec (aka 512 us) of RTT, so that the RTT-based allowance + * is below 1500 bytes after 6 * ~500 usec = 3ms. + */ +static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now, + int min_tso_segs) +{ + unsigned long bytes; + u32 r; + + bytes = sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift); + + r = tcp_min_rtt(tcp_sk(sk)) >> READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_rtt_log); + if (r < BITS_PER_TYPE(sk->sk_gso_max_size)) + bytes += sk->sk_gso_max_size >> r; + + bytes = min_t(unsigned long, bytes, sk->sk_gso_max_size); + + return max_t(u32, bytes / mss_now, min_tso_segs); +} + +/* Return the number of segments we want in the skb we are transmitting. + * See if congestion control module wants to decide; otherwise, autosize. + */ +static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now) +{ + const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; + u32 min_tso, tso_segs; + + min_tso = ca_ops->min_tso_segs ? + ca_ops->min_tso_segs(sk) : + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs); + + tso_segs = tcp_tso_autosize(sk, mss_now, min_tso); + return min_t(u32, tso_segs, sk->sk_gso_max_segs); +} + +/* Returns the portion of skb which can be sent right away */ +static unsigned int tcp_mss_split_point(const struct sock *sk, + const struct sk_buff *skb, + unsigned int mss_now, + unsigned int max_segs, + int nonagle) +{ + const struct tcp_sock *tp = tcp_sk(sk); + u32 partial, needed, window, max_len; + + window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; + max_len = mss_now * max_segs; + + if (likely(max_len <= window && skb != tcp_write_queue_tail(sk))) + return max_len; + + needed = min(skb->len, window); + + if (max_len <= needed) + return max_len; + + partial = needed % mss_now; + /* If last segment is not a full MSS, check if Nagle rules allow us + * to include this last segment in this skb. + * Otherwise, we'll split the skb at last MSS boundary + */ + if (tcp_nagle_check(partial != 0, tp, nonagle)) + return needed - partial; + + return needed; +} + +/* Can at least one segment of SKB be sent right now, according to the + * congestion window rules? If so, return how many segments are allowed. + */ +static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp, + const struct sk_buff *skb) +{ + u32 in_flight, cwnd, halfcwnd; + + /* Don't be strict about the congestion window for the final FIN. */ + if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) && + tcp_skb_pcount(skb) == 1) + return 1; + + in_flight = tcp_packets_in_flight(tp); + cwnd = tcp_snd_cwnd(tp); + if (in_flight >= cwnd) + return 0; + + /* For better scheduling, ensure we have at least + * 2 GSO packets in flight. + */ + halfcwnd = max(cwnd >> 1, 1U); + return min(halfcwnd, cwnd - in_flight); +} + +/* Initialize TSO state of a skb. + * This must be invoked the first time we consider transmitting + * SKB onto the wire. + */ +static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now) +{ + int tso_segs = tcp_skb_pcount(skb); + + if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { + tcp_set_skb_tso_segs(skb, mss_now); + tso_segs = tcp_skb_pcount(skb); + } + return tso_segs; +} + + +/* Return true if the Nagle test allows this packet to be + * sent now. + */ +static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb, + unsigned int cur_mss, int nonagle) +{ + /* Nagle rule does not apply to frames, which sit in the middle of the + * write_queue (they have no chances to get new data). + * + * This is implemented in the callers, where they modify the 'nonagle' + * argument based upon the location of SKB in the send queue. + */ + if (nonagle & TCP_NAGLE_PUSH) + return true; + + /* Don't use the nagle rule for urgent data (or for the final FIN). */ + if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) + return true; + + if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle)) + return true; + + return false; +} + +/* Does at least the first segment of SKB fit into the send window? */ +static bool tcp_snd_wnd_test(const struct tcp_sock *tp, + const struct sk_buff *skb, + unsigned int cur_mss) +{ + u32 end_seq = TCP_SKB_CB(skb)->end_seq; + + if (skb->len > cur_mss) + end_seq = TCP_SKB_CB(skb)->seq + cur_mss; + + return !after(end_seq, tcp_wnd_end(tp)); +} + +/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet + * which is put after SKB on the list. It is very much like + * tcp_fragment() except that it may make several kinds of assumptions + * in order to speed up the splitting operation. In particular, we + * know that all the data is in scatter-gather pages, and that the + * packet has never been sent out before (and thus is not cloned). + */ +static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, + unsigned int mss_now, gfp_t gfp) +{ + int nlen = skb->len - len; + struct sk_buff *buff; + u8 flags; + + /* All of a TSO frame must be composed of paged data. */ + if (skb->len != skb->data_len) + return tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE, + skb, len, mss_now, gfp); + + buff = tcp_stream_alloc_skb(sk, 0, gfp, true); + if (unlikely(!buff)) + return -ENOMEM; + skb_copy_decrypted(buff, skb); + mptcp_skb_ext_copy(buff, skb); + + sk_wmem_queued_add(sk, buff->truesize); + sk_mem_charge(sk, buff->truesize); + buff->truesize += nlen; + skb->truesize -= nlen; + + /* Correct the sequence numbers. */ + TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; + TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; + + /* PSH and FIN should only be set in the second packet. */ + flags = TCP_SKB_CB(skb)->tcp_flags; + TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH); + TCP_SKB_CB(buff)->tcp_flags = flags; + + tcp_skb_fragment_eor(skb, buff); + + skb_split(skb, buff, len); + tcp_fragment_tstamp(skb, buff); + + /* Fix up tso_factor for both original and new SKB. */ + tcp_set_skb_tso_segs(skb, mss_now); + tcp_set_skb_tso_segs(buff, mss_now); + + /* Link BUFF into the send queue. */ + __skb_header_release(buff); + tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE); + + return 0; +} + +/* Try to defer sending, if possible, in order to minimize the amount + * of TSO splitting we do. View it as a kind of TSO Nagle test. + * + * This algorithm is from John Heffner. + */ +static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb, + bool *is_cwnd_limited, + bool *is_rwnd_limited, + u32 max_segs) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + u32 send_win, cong_win, limit, in_flight; + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *head; + int win_divisor; + s64 delta; + + if (icsk->icsk_ca_state >= TCP_CA_Recovery) + goto send_now; + + /* Avoid bursty behavior by allowing defer + * only if the last write was recent (1 ms). + * Note that tp->tcp_wstamp_ns can be in the future if we have + * packets waiting in a qdisc or device for EDT delivery. + */ + delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC; + if (delta > 0) + goto send_now; + + in_flight = tcp_packets_in_flight(tp); + + BUG_ON(tcp_skb_pcount(skb) <= 1); + BUG_ON(tcp_snd_cwnd(tp) <= in_flight); + + send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; + + /* From in_flight test above, we know that cwnd > in_flight. */ + cong_win = (tcp_snd_cwnd(tp) - in_flight) * tp->mss_cache; + + limit = min(send_win, cong_win); + + /* If a full-sized TSO skb can be sent, do it. */ + if (limit >= max_segs * tp->mss_cache) + goto send_now; + + /* Middle in queue won't get any more data, full sendable already? */ + if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len)) + goto send_now; + + win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor); + if (win_divisor) { + u32 chunk = min(tp->snd_wnd, tcp_snd_cwnd(tp) * tp->mss_cache); + + /* If at least some fraction of a window is available, + * just use it. + */ + chunk /= win_divisor; + if (limit >= chunk) + goto send_now; + } else { + /* Different approach, try not to defer past a single + * ACK. Receiver should ACK every other full sized + * frame, so if we have space for more than 3 frames + * then send now. + */ + if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache) + goto send_now; + } + + /* TODO : use tsorted_sent_queue ? */ + head = tcp_rtx_queue_head(sk); + if (!head) + goto send_now; + delta = tp->tcp_clock_cache - head->tstamp; + /* If next ACK is likely to come too late (half srtt), do not defer */ + if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0) + goto send_now; + + /* Ok, it looks like it is advisable to defer. + * Three cases are tracked : + * 1) We are cwnd-limited + * 2) We are rwnd-limited + * 3) We are application limited. + */ + if (cong_win < send_win) { + if (cong_win <= skb->len) { + *is_cwnd_limited = true; + return true; + } + } else { + if (send_win <= skb->len) { + *is_rwnd_limited = true; + return true; + } + } + + /* If this packet won't get more data, do not wait. */ + if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) || + TCP_SKB_CB(skb)->eor) + goto send_now; + + return true; + +send_now: + return false; +} + +static inline void tcp_mtu_check_reprobe(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + struct net *net = sock_net(sk); + u32 interval; + s32 delta; + + interval = READ_ONCE(net->ipv4.sysctl_tcp_probe_interval); + delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp; + if (unlikely(delta >= interval * HZ)) { + int mss = tcp_current_mss(sk); + + /* Update current search range */ + icsk->icsk_mtup.probe_size = 0; + icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + + sizeof(struct tcphdr) + + icsk->icsk_af_ops->net_header_len; + icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); + + /* Update probe time stamp */ + icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; + } +} + +static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len) +{ + struct sk_buff *skb, *next; + + skb = tcp_send_head(sk); + tcp_for_write_queue_from_safe(skb, next, sk) { + if (len <= skb->len) + break; + + if (unlikely(TCP_SKB_CB(skb)->eor) || + tcp_has_tx_tstamp(skb) || + !skb_pure_zcopy_same(skb, next)) + return false; + + len -= skb->len; + } + + return true; +} + +/* Create a new MTU probe if we are ready. + * MTU probe is regularly attempting to increase the path MTU by + * deliberately sending larger packets. This discovers routing + * changes resulting in larger path MTUs. + * + * Returns 0 if we should wait to probe (no cwnd available), + * 1 if a probe was sent, + * -1 otherwise + */ +static int tcp_mtu_probe(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb, *nskb, *next; + struct net *net = sock_net(sk); + int probe_size; + int size_needed; + int copy, len; + int mss_now; + int interval; + + /* Not currently probing/verifying, + * not in recovery, + * have enough cwnd, and + * not SACKing (the variable headers throw things off) + */ + if (likely(!icsk->icsk_mtup.enabled || + icsk->icsk_mtup.probe_size || + inet_csk(sk)->icsk_ca_state != TCP_CA_Open || + tcp_snd_cwnd(tp) < 11 || + tp->rx_opt.num_sacks || tp->rx_opt.dsack)) + return -1; + + /* Use binary search for probe_size between tcp_mss_base, + * and current mss_clamp. if (search_high - search_low) + * smaller than a threshold, backoff from probing. + */ + mss_now = tcp_current_mss(sk); + probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high + + icsk->icsk_mtup.search_low) >> 1); + size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache; + interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low; + /* When misfortune happens, we are reprobing actively, + * and then reprobe timer has expired. We stick with current + * probing process by not resetting search range to its orignal. + */ + if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) || + interval < READ_ONCE(net->ipv4.sysctl_tcp_probe_threshold)) { + /* Check whether enough time has elaplased for + * another round of probing. + */ + tcp_mtu_check_reprobe(sk); + return -1; + } + + /* Have enough data in the send queue to probe? */ + if (tp->write_seq - tp->snd_nxt < size_needed) + return -1; + + if (tp->snd_wnd < size_needed) + return -1; + if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp))) + return 0; + + /* Do we need to wait to drain cwnd? With none in flight, don't stall */ + if (tcp_packets_in_flight(tp) + 2 > tcp_snd_cwnd(tp)) { + if (!tcp_packets_in_flight(tp)) + return -1; + else + return 0; + } + + if (!tcp_can_coalesce_send_queue_head(sk, probe_size)) + return -1; + + /* We're allowed to probe. Build it now. */ + nskb = tcp_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false); + if (!nskb) + return -1; + sk_wmem_queued_add(sk, nskb->truesize); + sk_mem_charge(sk, nskb->truesize); + + skb = tcp_send_head(sk); + skb_copy_decrypted(nskb, skb); + mptcp_skb_ext_copy(nskb, skb); + + TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; + TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; + TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK; + + tcp_insert_write_queue_before(nskb, skb, sk); + tcp_highest_sack_replace(sk, skb, nskb); + + len = 0; + tcp_for_write_queue_from_safe(skb, next, sk) { + copy = min_t(int, skb->len, probe_size - len); + skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); + + if (skb->len <= copy) { + /* We've eaten all the data from this skb. + * Throw it away. */ + TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; + /* If this is the last SKB we copy and eor is set + * we need to propagate it to the new skb. + */ + TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor; + tcp_skb_collapse_tstamp(nskb, skb); + tcp_unlink_write_queue(skb, sk); + tcp_wmem_free_skb(sk, skb); + } else { + TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags & + ~(TCPHDR_FIN|TCPHDR_PSH); + if (!skb_shinfo(skb)->nr_frags) { + skb_pull(skb, copy); + } else { + __pskb_trim_head(skb, copy); + tcp_set_skb_tso_segs(skb, mss_now); + } + TCP_SKB_CB(skb)->seq += copy; + } + + len += copy; + + if (len >= probe_size) + break; + } + tcp_init_tso_segs(nskb, nskb->len); + + /* We're ready to send. If this fails, the probe will + * be resegmented into mss-sized pieces by tcp_write_xmit(). + */ + if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { + /* Decrement cwnd here because we are sending + * effectively two packets. */ + tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) - 1); + tcp_event_new_data_sent(sk, nskb); + + icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len); + tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq; + tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq; + + return 1; + } + + return -1; +} + +static bool tcp_pacing_check(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (!tcp_needs_internal_pacing(sk)) + return false; + + if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache) + return false; + + if (!hrtimer_is_queued(&tp->pacing_timer)) { + hrtimer_start(&tp->pacing_timer, + ns_to_ktime(tp->tcp_wstamp_ns), + HRTIMER_MODE_ABS_PINNED_SOFT); + sock_hold(sk); + } + return true; +} + +static bool tcp_rtx_queue_empty_or_single_skb(const struct sock *sk) +{ + const struct rb_node *node = sk->tcp_rtx_queue.rb_node; + + /* No skb in the rtx queue. */ + if (!node) + return true; + + /* Only one skb in rtx queue. */ + return !node->rb_left && !node->rb_right; +} + +/* TCP Small Queues : + * Control number of packets in qdisc/devices to two packets / or ~1 ms. + * (These limits are doubled for retransmits) + * This allows for : + * - better RTT estimation and ACK scheduling + * - faster recovery + * - high rates + * Alas, some drivers / subsystems require a fair amount + * of queued bytes to ensure line rate. + * One example is wifi aggregation (802.11 AMPDU) + */ +static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb, + unsigned int factor) +{ + unsigned long limit; + + limit = max_t(unsigned long, + 2 * skb->truesize, + sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift)); + if (sk->sk_pacing_status == SK_PACING_NONE) + limit = min_t(unsigned long, limit, + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes)); + limit <<= factor; + + if (static_branch_unlikely(&tcp_tx_delay_enabled) && + tcp_sk(sk)->tcp_tx_delay) { + u64 extra_bytes = (u64)sk->sk_pacing_rate * tcp_sk(sk)->tcp_tx_delay; + + /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we + * approximate our needs assuming an ~100% skb->truesize overhead. + * USEC_PER_SEC is approximated by 2^20. + * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift. + */ + extra_bytes >>= (20 - 1); + limit += extra_bytes; + } + if (refcount_read(&sk->sk_wmem_alloc) > limit) { + /* Always send skb if rtx queue is empty or has one skb. + * No need to wait for TX completion to call us back, + * after softirq/tasklet schedule. + * This helps when TX completions are delayed too much. + */ + if (tcp_rtx_queue_empty_or_single_skb(sk)) + return false; + + set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags); + /* It is possible TX completion already happened + * before we set TSQ_THROTTLED, so we must + * test again the condition. + */ + smp_mb__after_atomic(); + if (refcount_read(&sk->sk_wmem_alloc) > limit) + return true; + } + return false; +} + +static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new) +{ + const u32 now = tcp_jiffies32; + enum tcp_chrono old = tp->chrono_type; + + if (old > TCP_CHRONO_UNSPEC) + tp->chrono_stat[old - 1] += now - tp->chrono_start; + tp->chrono_start = now; + tp->chrono_type = new; +} + +void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* If there are multiple conditions worthy of tracking in a + * chronograph then the highest priority enum takes precedence + * over the other conditions. So that if something "more interesting" + * starts happening, stop the previous chrono and start a new one. + */ + if (type > tp->chrono_type) + tcp_chrono_set(tp, type); +} + +void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type) +{ + struct tcp_sock *tp = tcp_sk(sk); + + + /* There are multiple conditions worthy of tracking in a + * chronograph, so that the highest priority enum takes + * precedence over the other conditions (see tcp_chrono_start). + * If a condition stops, we only stop chrono tracking if + * it's the "most interesting" or current chrono we are + * tracking and starts busy chrono if we have pending data. + */ + if (tcp_rtx_and_write_queues_empty(sk)) + tcp_chrono_set(tp, TCP_CHRONO_UNSPEC); + else if (type == tp->chrono_type) + tcp_chrono_set(tp, TCP_CHRONO_BUSY); +} + +/* This routine writes packets to the network. It advances the + * send_head. This happens as incoming acks open up the remote + * window for us. + * + * LARGESEND note: !tcp_urg_mode is overkill, only frames between + * snd_up-64k-mss .. snd_up cannot be large. However, taking into + * account rare use of URG, this is not a big flaw. + * + * Send at most one packet when push_one > 0. Temporarily ignore + * cwnd limit to force at most one packet out when push_one == 2. + + * Returns true, if no segments are in flight and we have queued segments, + * but cannot send anything now because of SWS or another problem. + */ +static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, + int push_one, gfp_t gfp) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + unsigned int tso_segs, sent_pkts; + int cwnd_quota; + int result; + bool is_cwnd_limited = false, is_rwnd_limited = false; + u32 max_segs; + + sent_pkts = 0; + + tcp_mstamp_refresh(tp); + if (!push_one) { + /* Do MTU probing. */ + result = tcp_mtu_probe(sk); + if (!result) { + return false; + } else if (result > 0) { + sent_pkts = 1; + } + } + + max_segs = tcp_tso_segs(sk, mss_now); + while ((skb = tcp_send_head(sk))) { + unsigned int limit; + + if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) { + /* "skb_mstamp_ns" is used as a start point for the retransmit timer */ + tp->tcp_wstamp_ns = tp->tcp_clock_cache; + skb_set_delivery_time(skb, tp->tcp_wstamp_ns, true); + list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue); + tcp_init_tso_segs(skb, mss_now); + goto repair; /* Skip network transmission */ + } + + if (tcp_pacing_check(sk)) + break; + + tso_segs = tcp_init_tso_segs(skb, mss_now); + BUG_ON(!tso_segs); + + cwnd_quota = tcp_cwnd_test(tp, skb); + if (!cwnd_quota) { + if (push_one == 2) + /* Force out a loss probe pkt. */ + cwnd_quota = 1; + else + break; + } + + if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) { + is_rwnd_limited = true; + break; + } + + if (tso_segs == 1) { + if (unlikely(!tcp_nagle_test(tp, skb, mss_now, + (tcp_skb_is_last(sk, skb) ? + nonagle : TCP_NAGLE_PUSH)))) + break; + } else { + if (!push_one && + tcp_tso_should_defer(sk, skb, &is_cwnd_limited, + &is_rwnd_limited, max_segs)) + break; + } + + limit = mss_now; + if (tso_segs > 1 && !tcp_urg_mode(tp)) + limit = tcp_mss_split_point(sk, skb, mss_now, + min_t(unsigned int, + cwnd_quota, + max_segs), + nonagle); + + if (skb->len > limit && + unlikely(tso_fragment(sk, skb, limit, mss_now, gfp))) + break; + + if (tcp_small_queue_check(sk, skb, 0)) + break; + + /* Argh, we hit an empty skb(), presumably a thread + * is sleeping in sendmsg()/sk_stream_wait_memory(). + * We do not want to send a pure-ack packet and have + * a strange looking rtx queue with empty packet(s). + */ + if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) + break; + + if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp))) + break; + +repair: + /* Advance the send_head. This one is sent out. + * This call will increment packets_out. + */ + tcp_event_new_data_sent(sk, skb); + + tcp_minshall_update(tp, mss_now, skb); + sent_pkts += tcp_skb_pcount(skb); + + if (push_one) + break; + } + + if (is_rwnd_limited) + tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED); + else + tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED); + + is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tcp_snd_cwnd(tp)); + if (likely(sent_pkts || is_cwnd_limited)) + tcp_cwnd_validate(sk, is_cwnd_limited); + + if (likely(sent_pkts)) { + if (tcp_in_cwnd_reduction(sk)) + tp->prr_out += sent_pkts; + + /* Send one loss probe per tail loss episode. */ + if (push_one != 2) + tcp_schedule_loss_probe(sk, false); + return false; + } + return !tp->packets_out && !tcp_write_queue_empty(sk); +} + +bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + u32 timeout, timeout_us, rto_delta_us; + int early_retrans; + + /* Don't do any loss probe on a Fast Open connection before 3WHS + * finishes. + */ + if (rcu_access_pointer(tp->fastopen_rsk)) + return false; + + early_retrans = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_early_retrans); + /* Schedule a loss probe in 2*RTT for SACK capable connections + * not in loss recovery, that are either limited by cwnd or application. + */ + if ((early_retrans != 3 && early_retrans != 4) || + !tp->packets_out || !tcp_is_sack(tp) || + (icsk->icsk_ca_state != TCP_CA_Open && + icsk->icsk_ca_state != TCP_CA_CWR)) + return false; + + /* Probe timeout is 2*rtt. Add minimum RTO to account + * for delayed ack when there's one outstanding packet. If no RTT + * sample is available then probe after TCP_TIMEOUT_INIT. + */ + if (tp->srtt_us) { + timeout_us = tp->srtt_us >> 2; + if (tp->packets_out == 1) + timeout_us += tcp_rto_min_us(sk); + else + timeout_us += TCP_TIMEOUT_MIN_US; + timeout = usecs_to_jiffies(timeout_us); + } else { + timeout = TCP_TIMEOUT_INIT; + } + + /* If the RTO formula yields an earlier time, then use that time. */ + rto_delta_us = advancing_rto ? + jiffies_to_usecs(inet_csk(sk)->icsk_rto) : + tcp_rto_delta_us(sk); /* How far in future is RTO? */ + if (rto_delta_us > 0) + timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us)); + + tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, TCP_RTO_MAX); + return true; +} + +/* Thanks to skb fast clones, we can detect if a prior transmit of + * a packet is still in a qdisc or driver queue. + * In this case, there is very little point doing a retransmit ! + */ +static bool skb_still_in_host_queue(struct sock *sk, + const struct sk_buff *skb) +{ + if (unlikely(skb_fclone_busy(sk, skb))) { + set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags); + smp_mb__after_atomic(); + if (skb_fclone_busy(sk, skb)) { + NET_INC_STATS(sock_net(sk), + LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES); + return true; + } + } + return false; +} + +/* When probe timeout (PTO) fires, try send a new segment if possible, else + * retransmit the last segment. + */ +void tcp_send_loss_probe(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + int pcount; + int mss = tcp_current_mss(sk); + + /* At most one outstanding TLP */ + if (tp->tlp_high_seq) + goto rearm_timer; + + tp->tlp_retrans = 0; + skb = tcp_send_head(sk); + if (skb && tcp_snd_wnd_test(tp, skb, mss)) { + pcount = tp->packets_out; + tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC); + if (tp->packets_out > pcount) + goto probe_sent; + goto rearm_timer; + } + skb = skb_rb_last(&sk->tcp_rtx_queue); + if (unlikely(!skb)) { + WARN_ONCE(tp->packets_out, + "invalid inflight: %u state %u cwnd %u mss %d\n", + tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss); + inet_csk(sk)->icsk_pending = 0; + return; + } + + if (skb_still_in_host_queue(sk, skb)) + goto rearm_timer; + + pcount = tcp_skb_pcount(skb); + if (WARN_ON(!pcount)) + goto rearm_timer; + + if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) { + if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, + (pcount - 1) * mss, mss, + GFP_ATOMIC))) + goto rearm_timer; + skb = skb_rb_next(skb); + } + + if (WARN_ON(!skb || !tcp_skb_pcount(skb))) + goto rearm_timer; + + if (__tcp_retransmit_skb(sk, skb, 1)) + goto rearm_timer; + + tp->tlp_retrans = 1; + +probe_sent: + /* Record snd_nxt for loss detection. */ + tp->tlp_high_seq = tp->snd_nxt; + + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES); + /* Reset s.t. tcp_rearm_rto will restart timer from now */ + inet_csk(sk)->icsk_pending = 0; +rearm_timer: + tcp_rearm_rto(sk); +} + +/* Push out any pending frames which were held back due to + * TCP_CORK or attempt at coalescing tiny packets. + * The socket must be locked by the caller. + */ +void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, + int nonagle) +{ + /* If we are closed, the bytes will have to remain here. + * In time closedown will finish, we empty the write queue and + * all will be happy. + */ + if (unlikely(sk->sk_state == TCP_CLOSE)) + return; + + if (tcp_write_xmit(sk, cur_mss, nonagle, 0, + sk_gfp_mask(sk, GFP_ATOMIC))) + tcp_check_probe_timer(sk); +} + +/* Send _single_ skb sitting at the send head. This function requires + * true push pending frames to setup probe timer etc. + */ +void tcp_push_one(struct sock *sk, unsigned int mss_now) +{ + struct sk_buff *skb = tcp_send_head(sk); + + BUG_ON(!skb || skb->len < mss_now); + + tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation); +} + +/* This function returns the amount that we can raise the + * usable window based on the following constraints + * + * 1. The window can never be shrunk once it is offered (RFC 793) + * 2. We limit memory per socket + * + * RFC 1122: + * "the suggested [SWS] avoidance algorithm for the receiver is to keep + * RECV.NEXT + RCV.WIN fixed until: + * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" + * + * i.e. don't raise the right edge of the window until you can raise + * it at least MSS bytes. + * + * Unfortunately, the recommended algorithm breaks header prediction, + * since header prediction assumes th->window stays fixed. + * + * Strictly speaking, keeping th->window fixed violates the receiver + * side SWS prevention criteria. The problem is that under this rule + * a stream of single byte packets will cause the right side of the + * window to always advance by a single byte. + * + * Of course, if the sender implements sender side SWS prevention + * then this will not be a problem. + * + * BSD seems to make the following compromise: + * + * If the free space is less than the 1/4 of the maximum + * space available and the free space is less than 1/2 mss, + * then set the window to 0. + * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] + * Otherwise, just prevent the window from shrinking + * and from being larger than the largest representable value. + * + * This prevents incremental opening of the window in the regime + * where TCP is limited by the speed of the reader side taking + * data out of the TCP receive queue. It does nothing about + * those cases where the window is constrained on the sender side + * because the pipeline is full. + * + * BSD also seems to "accidentally" limit itself to windows that are a + * multiple of MSS, at least until the free space gets quite small. + * This would appear to be a side effect of the mbuf implementation. + * Combining these two algorithms results in the observed behavior + * of having a fixed window size at almost all times. + * + * Below we obtain similar behavior by forcing the offered window to + * a multiple of the mss when it is feasible to do so. + * + * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. + * Regular options like TIMESTAMP are taken into account. + */ +u32 __tcp_select_window(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + struct net *net = sock_net(sk); + /* MSS for the peer's data. Previous versions used mss_clamp + * here. I don't know if the value based on our guesses + * of peer's MSS is better for the performance. It's more correct + * but may be worse for the performance because of rcv_mss + * fluctuations. --SAW 1998/11/1 + */ + int mss = icsk->icsk_ack.rcv_mss; + int free_space = tcp_space(sk); + int allowed_space = tcp_full_space(sk); + int full_space, window; + + if (sk_is_mptcp(sk)) + mptcp_space(sk, &free_space, &allowed_space); + + full_space = min_t(int, tp->window_clamp, allowed_space); + + if (unlikely(mss > full_space)) { + mss = full_space; + if (mss <= 0) + return 0; + } + + /* Only allow window shrink if the sysctl is enabled and we have + * a non-zero scaling factor in effect. + */ + if (READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) && tp->rx_opt.rcv_wscale) + goto shrink_window_allowed; + + /* do not allow window to shrink */ + + if (free_space < (full_space >> 1)) { + icsk->icsk_ack.quick = 0; + + if (tcp_under_memory_pressure(sk)) + tcp_adjust_rcv_ssthresh(sk); + + /* free_space might become our new window, make sure we don't + * increase it due to wscale. + */ + free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale); + + /* if free space is less than mss estimate, or is below 1/16th + * of the maximum allowed, try to move to zero-window, else + * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and + * new incoming data is dropped due to memory limits. + * With large window, mss test triggers way too late in order + * to announce zero window in time before rmem limit kicks in. + */ + if (free_space < (allowed_space >> 4) || free_space < mss) + return 0; + } + + if (free_space > tp->rcv_ssthresh) + free_space = tp->rcv_ssthresh; + + /* Don't do rounding if we are using window scaling, since the + * scaled window will not line up with the MSS boundary anyway. + */ + if (tp->rx_opt.rcv_wscale) { + window = free_space; + + /* Advertise enough space so that it won't get scaled away. + * Import case: prevent zero window announcement if + * 1<<rcv_wscale > mss. + */ + window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale)); + } else { + window = tp->rcv_wnd; + /* Get the largest window that is a nice multiple of mss. + * Window clamp already applied above. + * If our current window offering is within 1 mss of the + * free space we just keep it. This prevents the divide + * and multiply from happening most of the time. + * We also don't do any window rounding when the free space + * is too small. + */ + if (window <= free_space - mss || window > free_space) + window = rounddown(free_space, mss); + else if (mss == full_space && + free_space > window + (full_space >> 1)) + window = free_space; + } + + return window; + +shrink_window_allowed: + /* new window should always be an exact multiple of scaling factor */ + free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale); + + if (free_space < (full_space >> 1)) { + icsk->icsk_ack.quick = 0; + + if (tcp_under_memory_pressure(sk)) + tcp_adjust_rcv_ssthresh(sk); + + /* if free space is too low, return a zero window */ + if (free_space < (allowed_space >> 4) || free_space < mss || + free_space < (1 << tp->rx_opt.rcv_wscale)) + return 0; + } + + if (free_space > tp->rcv_ssthresh) { + free_space = tp->rcv_ssthresh; + /* new window should always be an exact multiple of scaling factor + * + * For this case, we ALIGN "up" (increase free_space) because + * we know free_space is not zero here, it has been reduced from + * the memory-based limit, and rcv_ssthresh is not a hard limit + * (unlike sk_rcvbuf). + */ + free_space = ALIGN(free_space, (1 << tp->rx_opt.rcv_wscale)); + } + + return free_space; +} + +void tcp_skb_collapse_tstamp(struct sk_buff *skb, + const struct sk_buff *next_skb) +{ + if (unlikely(tcp_has_tx_tstamp(next_skb))) { + const struct skb_shared_info *next_shinfo = + skb_shinfo(next_skb); + struct skb_shared_info *shinfo = skb_shinfo(skb); + + shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP; + shinfo->tskey = next_shinfo->tskey; + TCP_SKB_CB(skb)->txstamp_ack |= + TCP_SKB_CB(next_skb)->txstamp_ack; + } +} + +/* Collapses two adjacent SKB's during retransmission. */ +static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *next_skb = skb_rb_next(skb); + int next_skb_size; + + next_skb_size = next_skb->len; + + BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1); + + if (next_skb_size && !tcp_skb_shift(skb, next_skb, 1, next_skb_size)) + return false; + + tcp_highest_sack_replace(sk, next_skb, skb); + + /* Update sequence range on original skb. */ + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; + + /* Merge over control information. This moves PSH/FIN etc. over */ + TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags; + + /* All done, get rid of second SKB and account for it so + * packet counting does not break. + */ + TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS; + TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor; + + /* changed transmit queue under us so clear hints */ + tcp_clear_retrans_hints_partial(tp); + if (next_skb == tp->retransmit_skb_hint) + tp->retransmit_skb_hint = skb; + + tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb)); + + tcp_skb_collapse_tstamp(skb, next_skb); + + tcp_rtx_queue_unlink_and_free(next_skb, sk); + return true; +} + +/* Check if coalescing SKBs is legal. */ +static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb) +{ + if (tcp_skb_pcount(skb) > 1) + return false; + if (skb_cloned(skb)) + return false; + /* Some heuristics for collapsing over SACK'd could be invented */ + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) + return false; + + return true; +} + +/* Collapse packets in the retransmit queue to make to create + * less packets on the wire. This is only done on retransmission. + */ +static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, + int space) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb = to, *tmp; + bool first = true; + + if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)) + return; + if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) + return; + + skb_rbtree_walk_from_safe(skb, tmp) { + if (!tcp_can_collapse(sk, skb)) + break; + + if (!tcp_skb_can_collapse(to, skb)) + break; + + space -= skb->len; + + if (first) { + first = false; + continue; + } + + if (space < 0) + break; + + if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp))) + break; + + if (!tcp_collapse_retrans(sk, to)) + break; + } +} + +/* This retransmits one SKB. Policy decisions and retransmit queue + * state updates are done by the caller. Returns non-zero if an + * error occurred which prevented the send. + */ +int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + unsigned int cur_mss; + int diff, len, err; + int avail_wnd; + + /* Inconclusive MTU probe */ + if (icsk->icsk_mtup.probe_size) + icsk->icsk_mtup.probe_size = 0; + + if (skb_still_in_host_queue(sk, skb)) + return -EBUSY; + +start: + if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { + if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) { + TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN; + TCP_SKB_CB(skb)->seq++; + goto start; + } + if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) { + WARN_ON_ONCE(1); + return -EINVAL; + } + if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) + return -ENOMEM; + } + + if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) + return -EHOSTUNREACH; /* Routing failure or similar. */ + + cur_mss = tcp_current_mss(sk); + avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; + + /* If receiver has shrunk his window, and skb is out of + * new window, do not retransmit it. The exception is the + * case, when window is shrunk to zero. In this case + * our retransmit of one segment serves as a zero window probe. + */ + if (avail_wnd <= 0) { + if (TCP_SKB_CB(skb)->seq != tp->snd_una) + return -EAGAIN; + avail_wnd = cur_mss; + } + + len = cur_mss * segs; + if (len > avail_wnd) { + len = rounddown(avail_wnd, cur_mss); + if (!len) + len = avail_wnd; + } + if (skb->len > len) { + if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len, + cur_mss, GFP_ATOMIC)) + return -ENOMEM; /* We'll try again later. */ + } else { + if (skb_unclone_keeptruesize(skb, GFP_ATOMIC)) + return -ENOMEM; + + diff = tcp_skb_pcount(skb); + tcp_set_skb_tso_segs(skb, cur_mss); + diff -= tcp_skb_pcount(skb); + if (diff) + tcp_adjust_pcount(sk, skb, diff); + avail_wnd = min_t(int, avail_wnd, cur_mss); + if (skb->len < avail_wnd) + tcp_retrans_try_collapse(sk, skb, avail_wnd); + } + + /* RFC3168, section 6.1.1.1. ECN fallback */ + if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN) + tcp_ecn_clear_syn(sk, skb); + + /* Update global and local TCP statistics. */ + segs = tcp_skb_pcount(skb); + TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs); + if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); + tp->total_retrans += segs; + tp->bytes_retrans += skb->len; + + /* make sure skb->data is aligned on arches that require it + * and check if ack-trimming & collapsing extended the headroom + * beyond what csum_start can cover. + */ + if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) || + skb_headroom(skb) >= 0xFFFF)) { + struct sk_buff *nskb; + + tcp_skb_tsorted_save(skb) { + nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC); + if (nskb) { + nskb->dev = NULL; + err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC); + } else { + err = -ENOBUFS; + } + } tcp_skb_tsorted_restore(skb); + + if (!err) { + tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns); + tcp_rate_skb_sent(sk, skb); + } + } else { + err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); + } + + /* To avoid taking spuriously low RTT samples based on a timestamp + * for a transmit that never happened, always mark EVER_RETRANS + */ + TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS; + + if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG)) + tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB, + TCP_SKB_CB(skb)->seq, segs, err); + + if (likely(!err)) { + trace_tcp_retransmit_skb(sk, skb); + } else if (err != -EBUSY) { + NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs); + } + return err; +} + +int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) +{ + struct tcp_sock *tp = tcp_sk(sk); + int err = __tcp_retransmit_skb(sk, skb, segs); + + if (err == 0) { +#if FASTRETRANS_DEBUG > 0 + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { + net_dbg_ratelimited("retrans_out leaked\n"); + } +#endif + TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; + tp->retrans_out += tcp_skb_pcount(skb); + } + + /* Save stamp of the first (attempted) retransmit. */ + if (!tp->retrans_stamp) + tp->retrans_stamp = tcp_skb_timestamp(skb); + + if (tp->undo_retrans < 0) + tp->undo_retrans = 0; + tp->undo_retrans += tcp_skb_pcount(skb); + return err; +} + +/* This gets called after a retransmit timeout, and the initially + * retransmitted data is acknowledged. It tries to continue + * resending the rest of the retransmit queue, until either + * we've sent it all or the congestion window limit is reached. + */ +void tcp_xmit_retransmit_queue(struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + struct sk_buff *skb, *rtx_head, *hole = NULL; + struct tcp_sock *tp = tcp_sk(sk); + bool rearm_timer = false; + u32 max_segs; + int mib_idx; + + if (!tp->packets_out) + return; + + rtx_head = tcp_rtx_queue_head(sk); + skb = tp->retransmit_skb_hint ?: rtx_head; + max_segs = tcp_tso_segs(sk, tcp_current_mss(sk)); + skb_rbtree_walk_from(skb) { + __u8 sacked; + int segs; + + if (tcp_pacing_check(sk)) + break; + + /* we could do better than to assign each time */ + if (!hole) + tp->retransmit_skb_hint = skb; + + segs = tcp_snd_cwnd(tp) - tcp_packets_in_flight(tp); + if (segs <= 0) + break; + sacked = TCP_SKB_CB(skb)->sacked; + /* In case tcp_shift_skb_data() have aggregated large skbs, + * we need to make sure not sending too bigs TSO packets + */ + segs = min_t(int, segs, max_segs); + + if (tp->retrans_out >= tp->lost_out) { + break; + } else if (!(sacked & TCPCB_LOST)) { + if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED))) + hole = skb; + continue; + + } else { + if (icsk->icsk_ca_state != TCP_CA_Loss) + mib_idx = LINUX_MIB_TCPFASTRETRANS; + else + mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS; + } + + if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS)) + continue; + + if (tcp_small_queue_check(sk, skb, 1)) + break; + + if (tcp_retransmit_skb(sk, skb, segs)) + break; + + NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb)); + + if (tcp_in_cwnd_reduction(sk)) + tp->prr_out += tcp_skb_pcount(skb); + + if (skb == rtx_head && + icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT) + rearm_timer = true; + + } + if (rearm_timer) + tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + inet_csk(sk)->icsk_rto, + TCP_RTO_MAX); +} + +/* We allow to exceed memory limits for FIN packets to expedite + * connection tear down and (memory) recovery. + * Otherwise tcp_send_fin() could be tempted to either delay FIN + * or even be forced to close flow without any FIN. + * In general, we want to allow one skb per socket to avoid hangs + * with edge trigger epoll() + */ +void sk_forced_mem_schedule(struct sock *sk, int size) +{ + int delta, amt; + + delta = size - sk->sk_forward_alloc; + if (delta <= 0) + return; + amt = sk_mem_pages(delta); + sk_forward_alloc_add(sk, amt << PAGE_SHIFT); + sk_memory_allocated_add(sk, amt); + + if (mem_cgroup_sockets_enabled && sk->sk_memcg) + mem_cgroup_charge_skmem(sk->sk_memcg, amt, + gfp_memcg_charge() | __GFP_NOFAIL); +} + +/* Send a FIN. The caller locks the socket for us. + * We should try to send a FIN packet really hard, but eventually give up. + */ +void tcp_send_fin(struct sock *sk) +{ + struct sk_buff *skb, *tskb, *tail = tcp_write_queue_tail(sk); + struct tcp_sock *tp = tcp_sk(sk); + + /* Optimization, tack on the FIN if we have one skb in write queue and + * this skb was not yet sent, or we are under memory pressure. + * Note: in the latter case, FIN packet will be sent after a timeout, + * as TCP stack thinks it has already been transmitted. + */ + tskb = tail; + if (!tskb && tcp_under_memory_pressure(sk)) + tskb = skb_rb_last(&sk->tcp_rtx_queue); + + if (tskb) { + TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN; + TCP_SKB_CB(tskb)->end_seq++; + tp->write_seq++; + if (!tail) { + /* This means tskb was already sent. + * Pretend we included the FIN on previous transmit. + * We need to set tp->snd_nxt to the value it would have + * if FIN had been sent. This is because retransmit path + * does not change tp->snd_nxt. + */ + WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1); + return; + } + } else { + skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation); + if (unlikely(!skb)) + return; + + INIT_LIST_HEAD(&skb->tcp_tsorted_anchor); + skb_reserve(skb, MAX_TCP_HEADER); + sk_forced_mem_schedule(sk, skb->truesize); + /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ + tcp_init_nondata_skb(skb, tp->write_seq, + TCPHDR_ACK | TCPHDR_FIN); + tcp_queue_skb(sk, skb); + } + __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF); +} + +/* We get here when a process closes a file descriptor (either due to + * an explicit close() or as a byproduct of exit()'ing) and there + * was unread data in the receive queue. This behavior is recommended + * by RFC 2525, section 2.17. -DaveM + */ +void tcp_send_active_reset(struct sock *sk, gfp_t priority) +{ + struct sk_buff *skb; + + TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS); + + /* NOTE: No TCP options attached and we never retransmit this. */ + skb = alloc_skb(MAX_TCP_HEADER, priority); + if (!skb) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); + return; + } + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(skb, MAX_TCP_HEADER); + tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk), + TCPHDR_ACK | TCPHDR_RST); + tcp_mstamp_refresh(tcp_sk(sk)); + /* Send it off. */ + if (tcp_transmit_skb(sk, skb, 0, priority)) + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); + + /* skb of trace_tcp_send_reset() keeps the skb that caused RST, + * skb here is different to the troublesome skb, so use NULL + */ + trace_tcp_send_reset(sk, NULL); +} + +/* Send a crossed SYN-ACK during socket establishment. + * WARNING: This routine must only be called when we have already sent + * a SYN packet that crossed the incoming SYN that caused this routine + * to get called. If this assumption fails then the initial rcv_wnd + * and rcv_wscale values will not be correct. + */ +int tcp_send_synack(struct sock *sk) +{ + struct sk_buff *skb; + + skb = tcp_rtx_queue_head(sk); + if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) { + pr_err("%s: wrong queue state\n", __func__); + return -EFAULT; + } + if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) { + if (skb_cloned(skb)) { + struct sk_buff *nskb; + + tcp_skb_tsorted_save(skb) { + nskb = skb_copy(skb, GFP_ATOMIC); + } tcp_skb_tsorted_restore(skb); + if (!nskb) + return -ENOMEM; + INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor); + tcp_highest_sack_replace(sk, skb, nskb); + tcp_rtx_queue_unlink_and_free(skb, sk); + __skb_header_release(nskb); + tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb); + sk_wmem_queued_add(sk, nskb->truesize); + sk_mem_charge(sk, nskb->truesize); + skb = nskb; + } + + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK; + tcp_ecn_send_synack(sk, skb); + } + return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); +} + +/** + * tcp_make_synack - Allocate one skb and build a SYNACK packet. + * @sk: listener socket + * @dst: dst entry attached to the SYNACK. It is consumed and caller + * should not use it again. + * @req: request_sock pointer + * @foc: cookie for tcp fast open + * @synack_type: Type of synack to prepare + * @syn_skb: SYN packet just received. It could be NULL for rtx case. + */ +struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, + struct request_sock *req, + struct tcp_fastopen_cookie *foc, + enum tcp_synack_type synack_type, + struct sk_buff *syn_skb) +{ + struct inet_request_sock *ireq = inet_rsk(req); + const struct tcp_sock *tp = tcp_sk(sk); + struct tcp_md5sig_key *md5 = NULL; + struct tcp_out_options opts; + struct sk_buff *skb; + int tcp_header_size; + struct tcphdr *th; + int mss; + u64 now; + + skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); + if (unlikely(!skb)) { + dst_release(dst); + return NULL; + } + /* Reserve space for headers. */ + skb_reserve(skb, MAX_TCP_HEADER); + + switch (synack_type) { + case TCP_SYNACK_NORMAL: + skb_set_owner_w(skb, req_to_sk(req)); + break; + case TCP_SYNACK_COOKIE: + /* Under synflood, we do not attach skb to a socket, + * to avoid false sharing. + */ + break; + case TCP_SYNACK_FASTOPEN: + /* sk is a const pointer, because we want to express multiple + * cpu might call us concurrently. + * sk->sk_wmem_alloc in an atomic, we can promote to rw. + */ + skb_set_owner_w(skb, (struct sock *)sk); + break; + } + skb_dst_set(skb, dst); + + mss = tcp_mss_clamp(tp, dst_metric_advmss(dst)); + + memset(&opts, 0, sizeof(opts)); + now = tcp_clock_ns(); +#ifdef CONFIG_SYN_COOKIES + if (unlikely(synack_type == TCP_SYNACK_COOKIE && ireq->tstamp_ok)) + skb_set_delivery_time(skb, cookie_init_timestamp(req, now), + true); + else +#endif + { + skb_set_delivery_time(skb, now, true); + if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */ + tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb); + } + +#ifdef CONFIG_TCP_MD5SIG + rcu_read_lock(); + md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req)); +#endif + skb_set_hash(skb, READ_ONCE(tcp_rsk(req)->txhash), PKT_HASH_TYPE_L4); + /* bpf program will be interested in the tcp_flags */ + TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK; + tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5, + foc, synack_type, + syn_skb) + sizeof(*th); + + skb_push(skb, tcp_header_size); + skb_reset_transport_header(skb); + + th = (struct tcphdr *)skb->data; + memset(th, 0, sizeof(struct tcphdr)); + th->syn = 1; + th->ack = 1; + tcp_ecn_make_synack(req, th); + th->source = htons(ireq->ir_num); + th->dest = ireq->ir_rmt_port; + skb->mark = ireq->ir_mark; + skb->ip_summed = CHECKSUM_PARTIAL; + th->seq = htonl(tcp_rsk(req)->snt_isn); + /* XXX data is queued and acked as is. No buffer/window check */ + th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt); + + /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ + th->window = htons(min(req->rsk_rcv_wnd, 65535U)); + tcp_options_write(th, NULL, &opts); + th->doff = (tcp_header_size >> 2); + TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS); + +#ifdef CONFIG_TCP_MD5SIG + /* Okay, we have all we need - do the md5 hash if needed */ + if (md5) + tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location, + md5, req_to_sk(req), skb); + rcu_read_unlock(); +#endif + + bpf_skops_write_hdr_opt((struct sock *)sk, skb, req, syn_skb, + synack_type, &opts); + + skb_set_delivery_time(skb, now, true); + tcp_add_tx_delay(skb, tp); + + return skb; +} +EXPORT_SYMBOL(tcp_make_synack); + +static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + const struct tcp_congestion_ops *ca; + u32 ca_key = dst_metric(dst, RTAX_CC_ALGO); + + if (ca_key == TCP_CA_UNSPEC) + return; + + rcu_read_lock(); + ca = tcp_ca_find_key(ca_key); + if (likely(ca && bpf_try_module_get(ca, ca->owner))) { + bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner); + icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst); + icsk->icsk_ca_ops = ca; + } + rcu_read_unlock(); +} + +/* Do all connect socket setups that can be done AF independent. */ +static void tcp_connect_init(struct sock *sk) +{ + const struct dst_entry *dst = __sk_dst_get(sk); + struct tcp_sock *tp = tcp_sk(sk); + __u8 rcv_wscale; + u32 rcv_wnd; + + /* We'll fix this up when we get a response from the other end. + * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. + */ + tp->tcp_header_len = sizeof(struct tcphdr); + if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps)) + tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED; + +#ifdef CONFIG_TCP_MD5SIG + if (tp->af_specific->md5_lookup(sk, sk)) + tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; +#endif + + /* If user gave his TCP_MAXSEG, record it to clamp */ + if (tp->rx_opt.user_mss) + tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; + tp->max_window = 0; + tcp_mtup_init(sk); + tcp_sync_mss(sk, dst_mtu(dst)); + + tcp_ca_dst_init(sk, dst); + + if (!tp->window_clamp) + tp->window_clamp = dst_metric(dst, RTAX_WINDOW); + tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst)); + + tcp_initialize_rcv_mss(sk); + + /* limit the window selection if the user enforce a smaller rx buffer */ + if (sk->sk_userlocks & SOCK_RCVBUF_LOCK && + (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0)) + tp->window_clamp = tcp_full_space(sk); + + rcv_wnd = tcp_rwnd_init_bpf(sk); + if (rcv_wnd == 0) + rcv_wnd = dst_metric(dst, RTAX_INITRWND); + + tcp_select_initial_window(sk, tcp_full_space(sk), + tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), + &tp->rcv_wnd, + &tp->window_clamp, + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_window_scaling), + &rcv_wscale, + rcv_wnd); + + tp->rx_opt.rcv_wscale = rcv_wscale; + tp->rcv_ssthresh = tp->rcv_wnd; + + sk->sk_err = 0; + sock_reset_flag(sk, SOCK_DONE); + tp->snd_wnd = 0; + tcp_init_wl(tp, 0); + tcp_write_queue_purge(sk); + tp->snd_una = tp->write_seq; + tp->snd_sml = tp->write_seq; + tp->snd_up = tp->write_seq; + WRITE_ONCE(tp->snd_nxt, tp->write_seq); + + if (likely(!tp->repair)) + tp->rcv_nxt = 0; + else + tp->rcv_tstamp = tcp_jiffies32; + tp->rcv_wup = tp->rcv_nxt; + WRITE_ONCE(tp->copied_seq, tp->rcv_nxt); + + inet_csk(sk)->icsk_rto = tcp_timeout_init(sk); + inet_csk(sk)->icsk_retransmits = 0; + tcp_clear_retrans(tp); +} + +static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); + + tcb->end_seq += skb->len; + __skb_header_release(skb); + sk_wmem_queued_add(sk, skb->truesize); + sk_mem_charge(sk, skb->truesize); + WRITE_ONCE(tp->write_seq, tcb->end_seq); + tp->packets_out += tcp_skb_pcount(skb); +} + +/* Build and send a SYN with data and (cached) Fast Open cookie. However, + * queue a data-only packet after the regular SYN, such that regular SYNs + * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges + * only the SYN sequence, the data are retransmitted in the first ACK. + * If cookie is not cached or other error occurs, falls back to send a + * regular SYN with Fast Open cookie request option. + */ +static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_fastopen_request *fo = tp->fastopen_req; + int space, err = 0; + struct sk_buff *syn_data; + + tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */ + if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie)) + goto fallback; + + /* MSS for SYN-data is based on cached MSS and bounded by PMTU and + * user-MSS. Reserve maximum option space for middleboxes that add + * private TCP options. The cost is reduced data space in SYN :( + */ + tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp); + /* Sync mss_cache after updating the mss_clamp */ + tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); + + space = __tcp_mtu_to_mss(sk, icsk->icsk_pmtu_cookie) - + MAX_TCP_OPTION_SPACE; + + space = min_t(size_t, space, fo->size); + + /* limit to order-0 allocations */ + space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER)); + + syn_data = tcp_stream_alloc_skb(sk, space, sk->sk_allocation, false); + if (!syn_data) + goto fallback; + memcpy(syn_data->cb, syn->cb, sizeof(syn->cb)); + if (space) { + int copied = copy_from_iter(skb_put(syn_data, space), space, + &fo->data->msg_iter); + if (unlikely(!copied)) { + tcp_skb_tsorted_anchor_cleanup(syn_data); + kfree_skb(syn_data); + goto fallback; + } + if (copied != space) { + skb_trim(syn_data, copied); + space = copied; + } + skb_zcopy_set(syn_data, fo->uarg, NULL); + } + /* No more data pending in inet_wait_for_connect() */ + if (space == fo->size) + fo->data = NULL; + fo->copied = space; + + tcp_connect_queue_skb(sk, syn_data); + if (syn_data->len) + tcp_chrono_start(sk, TCP_CHRONO_BUSY); + + err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation); + + skb_set_delivery_time(syn, syn_data->skb_mstamp_ns, true); + + /* Now full SYN+DATA was cloned and sent (or not), + * remove the SYN from the original skb (syn_data) + * we keep in write queue in case of a retransmit, as we + * also have the SYN packet (with no data) in the same queue. + */ + TCP_SKB_CB(syn_data)->seq++; + TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH; + if (!err) { + tp->syn_data = (fo->copied > 0); + tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data); + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT); + goto done; + } + + /* data was not sent, put it in write_queue */ + __skb_queue_tail(&sk->sk_write_queue, syn_data); + tp->packets_out -= tcp_skb_pcount(syn_data); + +fallback: + /* Send a regular SYN with Fast Open cookie request option */ + if (fo->cookie.len > 0) + fo->cookie.len = 0; + err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation); + if (err) + tp->syn_fastopen = 0; +done: + fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */ + return err; +} + +/* Build a SYN and send it off. */ +int tcp_connect(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *buff; + int err; + + tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL); + + if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) + return -EHOSTUNREACH; /* Routing failure or similar. */ + + tcp_connect_init(sk); + + if (unlikely(tp->repair)) { + tcp_finish_connect(sk, NULL); + return 0; + } + + buff = tcp_stream_alloc_skb(sk, 0, sk->sk_allocation, true); + if (unlikely(!buff)) + return -ENOBUFS; + + tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN); + tcp_mstamp_refresh(tp); + tp->retrans_stamp = tcp_time_stamp(tp); + tcp_connect_queue_skb(sk, buff); + tcp_ecn_send_syn(sk, buff); + tcp_rbtree_insert(&sk->tcp_rtx_queue, buff); + + /* Send off SYN; include data in Fast Open. */ + err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) : + tcp_transmit_skb(sk, buff, 1, sk->sk_allocation); + if (err == -ECONNREFUSED) + return err; + + /* We change tp->snd_nxt after the tcp_transmit_skb() call + * in order to make this packet get counted in tcpOutSegs. + */ + WRITE_ONCE(tp->snd_nxt, tp->write_seq); + tp->pushed_seq = tp->write_seq; + buff = tcp_send_head(sk); + if (unlikely(buff)) { + WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq); + tp->pushed_seq = TCP_SKB_CB(buff)->seq; + } + TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS); + + /* Timer for repeating the SYN until an answer. */ + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + inet_csk(sk)->icsk_rto, TCP_RTO_MAX); + return 0; +} +EXPORT_SYMBOL(tcp_connect); + +/* Send out a delayed ack, the caller does the policy checking + * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() + * for details. + */ +void tcp_send_delayed_ack(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + int ato = icsk->icsk_ack.ato; + unsigned long timeout; + + if (ato > TCP_DELACK_MIN) { + const struct tcp_sock *tp = tcp_sk(sk); + int max_ato = HZ / 2; + + if (inet_csk_in_pingpong_mode(sk) || + (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)) + max_ato = TCP_DELACK_MAX; + + /* Slow path, intersegment interval is "high". */ + + /* If some rtt estimate is known, use it to bound delayed ack. + * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements + * directly. + */ + if (tp->srtt_us) { + int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3), + TCP_DELACK_MIN); + + if (rtt < max_ato) + max_ato = rtt; + } + + ato = min(ato, max_ato); + } + + ato = min_t(u32, ato, inet_csk(sk)->icsk_delack_max); + + /* Stay within the limit we were given */ + timeout = jiffies + ato; + + /* Use new timeout only if there wasn't a older one earlier. */ + if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { + /* If delack timer is about to expire, send ACK now. */ + if (time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { + tcp_send_ack(sk); + return; + } + + if (!time_before(timeout, icsk->icsk_ack.timeout)) + timeout = icsk->icsk_ack.timeout; + } + icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; + icsk->icsk_ack.timeout = timeout; + sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); +} + +/* This routine sends an ack and also updates the window. */ +void __tcp_send_ack(struct sock *sk, u32 rcv_nxt) +{ + struct sk_buff *buff; + + /* If we have been reset, we may not send again. */ + if (sk->sk_state == TCP_CLOSE) + return; + + /* We are not putting this on the write queue, so + * tcp_transmit_skb() will set the ownership to this + * sock. + */ + buff = alloc_skb(MAX_TCP_HEADER, + sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN)); + if (unlikely(!buff)) { + struct inet_connection_sock *icsk = inet_csk(sk); + unsigned long delay; + + delay = TCP_DELACK_MAX << icsk->icsk_ack.retry; + if (delay < TCP_RTO_MAX) + icsk->icsk_ack.retry++; + inet_csk_schedule_ack(sk); + icsk->icsk_ack.ato = TCP_ATO_MIN; + inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, delay, TCP_RTO_MAX); + return; + } + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(buff, MAX_TCP_HEADER); + tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK); + + /* We do not want pure acks influencing TCP Small Queues or fq/pacing + * too much. + * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784 + */ + skb_set_tcp_pure_ack(buff); + + /* Send it off, this clears delayed acks for us. */ + __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt); +} +EXPORT_SYMBOL_GPL(__tcp_send_ack); + +void tcp_send_ack(struct sock *sk) +{ + __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt); +} + +/* This routine sends a packet with an out of date sequence + * number. It assumes the other end will try to ack it. + * + * Question: what should we make while urgent mode? + * 4.4BSD forces sending single byte of data. We cannot send + * out of window data, because we have SND.NXT==SND.MAX... + * + * Current solution: to send TWO zero-length segments in urgent mode: + * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is + * out-of-date with SND.UNA-1 to probe window. + */ +static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + + /* We don't queue it, tcp_transmit_skb() sets ownership. */ + skb = alloc_skb(MAX_TCP_HEADER, + sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN)); + if (!skb) + return -1; + + /* Reserve space for headers and set control bits. */ + skb_reserve(skb, MAX_TCP_HEADER); + /* Use a previous sequence. This should cause the other + * end to send an ack. Don't queue or clone SKB, just + * send it. + */ + tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK); + NET_INC_STATS(sock_net(sk), mib); + return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0); +} + +/* Called from setsockopt( ... TCP_REPAIR ) */ +void tcp_send_window_probe(struct sock *sk) +{ + if (sk->sk_state == TCP_ESTABLISHED) { + tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1; + tcp_mstamp_refresh(tcp_sk(sk)); + tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE); + } +} + +/* Initiate keepalive or window probe from timer. */ +int tcp_write_wakeup(struct sock *sk, int mib) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + + if (sk->sk_state == TCP_CLOSE) + return -1; + + skb = tcp_send_head(sk); + if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) { + int err; + unsigned int mss = tcp_current_mss(sk); + unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; + + if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) + tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; + + /* We are probing the opening of a window + * but the window size is != 0 + * must have been a result SWS avoidance ( sender ) + */ + if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || + skb->len > mss) { + seg_size = min(seg_size, mss); + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; + if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE, + skb, seg_size, mss, GFP_ATOMIC)) + return -1; + } else if (!tcp_skb_pcount(skb)) + tcp_set_skb_tso_segs(skb, mss); + + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; + err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); + if (!err) + tcp_event_new_data_sent(sk, skb); + return err; + } else { + if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF)) + tcp_xmit_probe_skb(sk, 1, mib); + return tcp_xmit_probe_skb(sk, 0, mib); + } +} + +/* A window probe timeout has occurred. If window is not closed send + * a partial packet else a zero probe. + */ +void tcp_send_probe0(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + struct net *net = sock_net(sk); + unsigned long timeout; + int err; + + err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE); + + if (tp->packets_out || tcp_write_queue_empty(sk)) { + /* Cancel probe timer, if it is not required. */ + icsk->icsk_probes_out = 0; + icsk->icsk_backoff = 0; + icsk->icsk_probes_tstamp = 0; + return; + } + + icsk->icsk_probes_out++; + if (err <= 0) { + if (icsk->icsk_backoff < READ_ONCE(net->ipv4.sysctl_tcp_retries2)) + icsk->icsk_backoff++; + timeout = tcp_probe0_when(sk, TCP_RTO_MAX); + } else { + /* If packet was not sent due to local congestion, + * Let senders fight for local resources conservatively. + */ + timeout = TCP_RESOURCE_PROBE_INTERVAL; + } + + timeout = tcp_clamp_probe0_to_user_timeout(sk, timeout); + tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX); +} + +int tcp_rtx_synack(const struct sock *sk, struct request_sock *req) +{ + const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific; + struct flowi fl; + int res; + + /* Paired with WRITE_ONCE() in sock_setsockopt() */ + if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED) + WRITE_ONCE(tcp_rsk(req)->txhash, net_tx_rndhash()); + res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL, + NULL); + if (!res) { + TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS); + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); + if (unlikely(tcp_passive_fastopen(sk))) + tcp_sk(sk)->total_retrans++; + trace_tcp_retransmit_synack(sk, req); + } + return res; +} +EXPORT_SYMBOL(tcp_rtx_synack); |