diff options
Diffstat (limited to 'net/netfilter/nf_conntrack_proto_tcp.c')
| -rw-r--r-- | net/netfilter/nf_conntrack_proto_tcp.c | 1616 |
1 files changed, 1616 insertions, 0 deletions
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c new file mode 100644 index 000000000..3ac1af6f5 --- /dev/null +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -0,0 +1,1616 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* (C) 1999-2001 Paul `Rusty' Russell + * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> + * (C) 2002-2013 Jozsef Kadlecsik <kadlec@netfilter.org> + * (C) 2006-2012 Patrick McHardy <kaber@trash.net> + */ + +#include <linux/types.h> +#include <linux/timer.h> +#include <linux/module.h> +#include <linux/in.h> +#include <linux/tcp.h> +#include <linux/spinlock.h> +#include <linux/skbuff.h> +#include <linux/ipv6.h> +#include <net/ip6_checksum.h> +#include <asm/unaligned.h> + +#include <net/tcp.h> + +#include <linux/netfilter.h> +#include <linux/netfilter_ipv4.h> +#include <linux/netfilter_ipv6.h> +#include <net/netfilter/nf_conntrack.h> +#include <net/netfilter/nf_conntrack_l4proto.h> +#include <net/netfilter/nf_conntrack_ecache.h> +#include <net/netfilter/nf_conntrack_seqadj.h> +#include <net/netfilter/nf_conntrack_synproxy.h> +#include <net/netfilter/nf_conntrack_timeout.h> +#include <net/netfilter/nf_log.h> +#include <net/netfilter/ipv4/nf_conntrack_ipv4.h> +#include <net/netfilter/ipv6/nf_conntrack_ipv6.h> + + /* FIXME: Examine ipfilter's timeouts and conntrack transitions more + closely. They're more complex. --RR */ + +static const char *const tcp_conntrack_names[] = { + "NONE", + "SYN_SENT", + "SYN_RECV", + "ESTABLISHED", + "FIN_WAIT", + "CLOSE_WAIT", + "LAST_ACK", + "TIME_WAIT", + "CLOSE", + "SYN_SENT2", +}; + +enum nf_ct_tcp_action { + NFCT_TCP_IGNORE, + NFCT_TCP_INVALID, + NFCT_TCP_ACCEPT, +}; + +#define SECS * HZ +#define MINS * 60 SECS +#define HOURS * 60 MINS +#define DAYS * 24 HOURS + +static const unsigned int tcp_timeouts[TCP_CONNTRACK_TIMEOUT_MAX] = { + [TCP_CONNTRACK_SYN_SENT] = 2 MINS, + [TCP_CONNTRACK_SYN_RECV] = 60 SECS, + [TCP_CONNTRACK_ESTABLISHED] = 5 DAYS, + [TCP_CONNTRACK_FIN_WAIT] = 2 MINS, + [TCP_CONNTRACK_CLOSE_WAIT] = 60 SECS, + [TCP_CONNTRACK_LAST_ACK] = 30 SECS, + [TCP_CONNTRACK_TIME_WAIT] = 2 MINS, + [TCP_CONNTRACK_CLOSE] = 10 SECS, + [TCP_CONNTRACK_SYN_SENT2] = 2 MINS, +/* RFC1122 says the R2 limit should be at least 100 seconds. + Linux uses 15 packets as limit, which corresponds + to ~13-30min depending on RTO. */ + [TCP_CONNTRACK_RETRANS] = 5 MINS, + [TCP_CONNTRACK_UNACK] = 5 MINS, +}; + +#define sNO TCP_CONNTRACK_NONE +#define sSS TCP_CONNTRACK_SYN_SENT +#define sSR TCP_CONNTRACK_SYN_RECV +#define sES TCP_CONNTRACK_ESTABLISHED +#define sFW TCP_CONNTRACK_FIN_WAIT +#define sCW TCP_CONNTRACK_CLOSE_WAIT +#define sLA TCP_CONNTRACK_LAST_ACK +#define sTW TCP_CONNTRACK_TIME_WAIT +#define sCL TCP_CONNTRACK_CLOSE +#define sS2 TCP_CONNTRACK_SYN_SENT2 +#define sIV TCP_CONNTRACK_MAX +#define sIG TCP_CONNTRACK_IGNORE + +/* What TCP flags are set from RST/SYN/FIN/ACK. */ +enum tcp_bit_set { + TCP_SYN_SET, + TCP_SYNACK_SET, + TCP_FIN_SET, + TCP_ACK_SET, + TCP_RST_SET, + TCP_NONE_SET, +}; + +/* + * The TCP state transition table needs a few words... + * + * We are the man in the middle. All the packets go through us + * but might get lost in transit to the destination. + * It is assumed that the destinations can't receive segments + * we haven't seen. + * + * The checked segment is in window, but our windows are *not* + * equivalent with the ones of the sender/receiver. We always + * try to guess the state of the current sender. + * + * The meaning of the states are: + * + * NONE: initial state + * SYN_SENT: SYN-only packet seen + * SYN_SENT2: SYN-only packet seen from reply dir, simultaneous open + * SYN_RECV: SYN-ACK packet seen + * ESTABLISHED: ACK packet seen + * FIN_WAIT: FIN packet seen + * CLOSE_WAIT: ACK seen (after FIN) + * LAST_ACK: FIN seen (after FIN) + * TIME_WAIT: last ACK seen + * CLOSE: closed connection (RST) + * + * Packets marked as IGNORED (sIG): + * if they may be either invalid or valid + * and the receiver may send back a connection + * closing RST or a SYN/ACK. + * + * Packets marked as INVALID (sIV): + * if we regard them as truly invalid packets + */ +static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = { + { +/* ORIGINAL */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*syn*/ { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sS2 }, +/* + * sNO -> sSS Initialize a new connection + * sSS -> sSS Retransmitted SYN + * sS2 -> sS2 Late retransmitted SYN + * sSR -> sIG + * sES -> sIG Error: SYNs in window outside the SYN_SENT state + * are errors. Receiver will reply with RST + * and close the connection. + * Or we are not in sync and hold a dead connection. + * sFW -> sIG + * sCW -> sIG + * sLA -> sIG + * sTW -> sSS Reopened connection (RFC 1122). + * sCL -> sSS + */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*synack*/ { sIV, sIV, sSR, sIV, sIV, sIV, sIV, sIV, sIV, sSR }, +/* + * sNO -> sIV Too late and no reason to do anything + * sSS -> sIV Client can't send SYN and then SYN/ACK + * sS2 -> sSR SYN/ACK sent to SYN2 in simultaneous open + * sSR -> sSR Late retransmitted SYN/ACK in simultaneous open + * sES -> sIV Invalid SYN/ACK packets sent by the client + * sFW -> sIV + * sCW -> sIV + * sLA -> sIV + * sTW -> sIV + * sCL -> sIV + */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV }, +/* + * sNO -> sIV Too late and no reason to do anything... + * sSS -> sIV Client migth not send FIN in this state: + * we enforce waiting for a SYN/ACK reply first. + * sS2 -> sIV + * sSR -> sFW Close started. + * sES -> sFW + * sFW -> sLA FIN seen in both directions, waiting for + * the last ACK. + * Migth be a retransmitted FIN as well... + * sCW -> sLA + * sLA -> sLA Retransmitted FIN. Remain in the same state. + * sTW -> sTW + * sCL -> sCL + */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*ack*/ { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV }, +/* + * sNO -> sES Assumed. + * sSS -> sIV ACK is invalid: we haven't seen a SYN/ACK yet. + * sS2 -> sIV + * sSR -> sES Established state is reached. + * sES -> sES :-) + * sFW -> sCW Normal close request answered by ACK. + * sCW -> sCW + * sLA -> sTW Last ACK detected (RFC5961 challenged) + * sTW -> sTW Retransmitted last ACK. Remain in the same state. + * sCL -> sCL + */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL }, +/*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV } + }, + { +/* REPLY */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*syn*/ { sIV, sS2, sIV, sIV, sIV, sIV, sIV, sSS, sIV, sS2 }, +/* + * sNO -> sIV Never reached. + * sSS -> sS2 Simultaneous open + * sS2 -> sS2 Retransmitted simultaneous SYN + * sSR -> sIV Invalid SYN packets sent by the server + * sES -> sIV + * sFW -> sIV + * sCW -> sIV + * sLA -> sIV + * sTW -> sSS Reopened connection, but server may have switched role + * sCL -> sIV + */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*synack*/ { sIV, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIG, sSR }, +/* + * sSS -> sSR Standard open. + * sS2 -> sSR Simultaneous open + * sSR -> sIG Retransmitted SYN/ACK, ignore it. + * sES -> sIG Late retransmitted SYN/ACK? + * sFW -> sIG Might be SYN/ACK answering ignored SYN + * sCW -> sIG + * sLA -> sIG + * sTW -> sIG + * sCL -> sIG + */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV }, +/* + * sSS -> sIV Server might not send FIN in this state. + * sS2 -> sIV + * sSR -> sFW Close started. + * sES -> sFW + * sFW -> sLA FIN seen in both directions. + * sCW -> sLA + * sLA -> sLA Retransmitted FIN. + * sTW -> sTW + * sCL -> sCL + */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*ack*/ { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIG }, +/* + * sSS -> sIG Might be a half-open connection. + * sS2 -> sIG + * sSR -> sSR Might answer late resent SYN. + * sES -> sES :-) + * sFW -> sCW Normal close request answered by ACK. + * sCW -> sCW + * sLA -> sTW Last ACK detected (RFC5961 challenged) + * sTW -> sTW Retransmitted last ACK. + * sCL -> sCL + */ +/* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ +/*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL }, +/*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV } + } +}; + +#ifdef CONFIG_NF_CONNTRACK_PROCFS +/* Print out the private part of the conntrack. */ +static void tcp_print_conntrack(struct seq_file *s, struct nf_conn *ct) +{ + if (test_bit(IPS_OFFLOAD_BIT, &ct->status)) + return; + + seq_printf(s, "%s ", tcp_conntrack_names[ct->proto.tcp.state]); +} +#endif + +static unsigned int get_conntrack_index(const struct tcphdr *tcph) +{ + if (tcph->rst) return TCP_RST_SET; + else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET); + else if (tcph->fin) return TCP_FIN_SET; + else if (tcph->ack) return TCP_ACK_SET; + else return TCP_NONE_SET; +} + +/* TCP connection tracking based on 'Real Stateful TCP Packet Filtering + in IP Filter' by Guido van Rooij. + + http://www.sane.nl/events/sane2000/papers.html + http://www.darkart.com/mirrors/www.obfuscation.org/ipf/ + + The boundaries and the conditions are changed according to RFC793: + the packet must intersect the window (i.e. segments may be + after the right or before the left edge) and thus receivers may ACK + segments after the right edge of the window. + + td_maxend = max(sack + max(win,1)) seen in reply packets + td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets + td_maxwin += seq + len - sender.td_maxend + if seq + len > sender.td_maxend + td_end = max(seq + len) seen in sent packets + + I. Upper bound for valid data: seq <= sender.td_maxend + II. Lower bound for valid data: seq + len >= sender.td_end - receiver.td_maxwin + III. Upper bound for valid (s)ack: sack <= receiver.td_end + IV. Lower bound for valid (s)ack: sack >= receiver.td_end - MAXACKWINDOW + + where sack is the highest right edge of sack block found in the packet + or ack in the case of packet without SACK option. + + The upper bound limit for a valid (s)ack is not ignored - + we doesn't have to deal with fragments. +*/ + +static inline __u32 segment_seq_plus_len(__u32 seq, + size_t len, + unsigned int dataoff, + const struct tcphdr *tcph) +{ + /* XXX Should I use payload length field in IP/IPv6 header ? + * - YK */ + return (seq + len - dataoff - tcph->doff*4 + + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0)); +} + +/* Fixme: what about big packets? */ +#define MAXACKWINCONST 66000 +#define MAXACKWINDOW(sender) \ + ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin \ + : MAXACKWINCONST) + +/* + * Simplified tcp_parse_options routine from tcp_input.c + */ +static void tcp_options(const struct sk_buff *skb, + unsigned int dataoff, + const struct tcphdr *tcph, + struct ip_ct_tcp_state *state) +{ + unsigned char buff[(15 * 4) - sizeof(struct tcphdr)]; + const unsigned char *ptr; + int length = (tcph->doff*4) - sizeof(struct tcphdr); + + if (!length) + return; + + ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr), + length, buff); + if (!ptr) + return; + + state->td_scale = 0; + state->flags &= IP_CT_TCP_FLAG_BE_LIBERAL; + + while (length > 0) { + int opcode=*ptr++; + int opsize; + + switch (opcode) { + case TCPOPT_EOL: + return; + case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ + length--; + continue; + default: + if (length < 2) + return; + opsize=*ptr++; + if (opsize < 2) /* "silly options" */ + return; + if (opsize > length) + return; /* don't parse partial options */ + + if (opcode == TCPOPT_SACK_PERM + && opsize == TCPOLEN_SACK_PERM) + state->flags |= IP_CT_TCP_FLAG_SACK_PERM; + else if (opcode == TCPOPT_WINDOW + && opsize == TCPOLEN_WINDOW) { + state->td_scale = *(u_int8_t *)ptr; + + if (state->td_scale > TCP_MAX_WSCALE) + state->td_scale = TCP_MAX_WSCALE; + + state->flags |= + IP_CT_TCP_FLAG_WINDOW_SCALE; + } + ptr += opsize - 2; + length -= opsize; + } + } +} + +static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff, + const struct tcphdr *tcph, __u32 *sack) +{ + unsigned char buff[(15 * 4) - sizeof(struct tcphdr)]; + const unsigned char *ptr; + int length = (tcph->doff*4) - sizeof(struct tcphdr); + __u32 tmp; + + if (!length) + return; + + ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr), + length, buff); + if (!ptr) + return; + + /* Fast path for timestamp-only option */ + if (length == TCPOLEN_TSTAMP_ALIGNED + && *(__be32 *)ptr == htonl((TCPOPT_NOP << 24) + | (TCPOPT_NOP << 16) + | (TCPOPT_TIMESTAMP << 8) + | TCPOLEN_TIMESTAMP)) + return; + + while (length > 0) { + int opcode = *ptr++; + int opsize, i; + + switch (opcode) { + case TCPOPT_EOL: + return; + case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ + length--; + continue; + default: + if (length < 2) + return; + opsize = *ptr++; + if (opsize < 2) /* "silly options" */ + return; + if (opsize > length) + return; /* don't parse partial options */ + + if (opcode == TCPOPT_SACK + && opsize >= (TCPOLEN_SACK_BASE + + TCPOLEN_SACK_PERBLOCK) + && !((opsize - TCPOLEN_SACK_BASE) + % TCPOLEN_SACK_PERBLOCK)) { + for (i = 0; + i < (opsize - TCPOLEN_SACK_BASE); + i += TCPOLEN_SACK_PERBLOCK) { + tmp = get_unaligned_be32((__be32 *)(ptr+i)+1); + + if (after(tmp, *sack)) + *sack = tmp; + } + return; + } + ptr += opsize - 2; + length -= opsize; + } + } +} + +static void tcp_init_sender(struct ip_ct_tcp_state *sender, + struct ip_ct_tcp_state *receiver, + const struct sk_buff *skb, + unsigned int dataoff, + const struct tcphdr *tcph, + u32 end, u32 win) +{ + /* SYN-ACK in reply to a SYN + * or SYN from reply direction in simultaneous open. + */ + sender->td_end = + sender->td_maxend = end; + sender->td_maxwin = (win == 0 ? 1 : win); + + tcp_options(skb, dataoff, tcph, sender); + /* RFC 1323: + * Both sides must send the Window Scale option + * to enable window scaling in either direction. + */ + if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE && + receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE)) { + sender->td_scale = 0; + receiver->td_scale = 0; + } +} + +__printf(6, 7) +static enum nf_ct_tcp_action nf_tcp_log_invalid(const struct sk_buff *skb, + const struct nf_conn *ct, + const struct nf_hook_state *state, + const struct ip_ct_tcp_state *sender, + enum nf_ct_tcp_action ret, + const char *fmt, ...) +{ + const struct nf_tcp_net *tn = nf_tcp_pernet(nf_ct_net(ct)); + struct va_format vaf; + va_list args; + bool be_liberal; + + be_liberal = sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL || tn->tcp_be_liberal; + if (be_liberal) + return NFCT_TCP_ACCEPT; + + va_start(args, fmt); + vaf.fmt = fmt; + vaf.va = &args; + nf_ct_l4proto_log_invalid(skb, ct, state, "%pV", &vaf); + va_end(args); + + return ret; +} + +static enum nf_ct_tcp_action +tcp_in_window(struct nf_conn *ct, enum ip_conntrack_dir dir, + unsigned int index, const struct sk_buff *skb, + unsigned int dataoff, const struct tcphdr *tcph, + const struct nf_hook_state *hook_state) +{ + struct ip_ct_tcp *state = &ct->proto.tcp; + struct ip_ct_tcp_state *sender = &state->seen[dir]; + struct ip_ct_tcp_state *receiver = &state->seen[!dir]; + __u32 seq, ack, sack, end, win, swin; + bool in_recv_win, seq_ok; + s32 receiver_offset; + u16 win_raw; + + /* + * Get the required data from the packet. + */ + seq = ntohl(tcph->seq); + ack = sack = ntohl(tcph->ack_seq); + win_raw = ntohs(tcph->window); + win = win_raw; + end = segment_seq_plus_len(seq, skb->len, dataoff, tcph); + + if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM) + tcp_sack(skb, dataoff, tcph, &sack); + + /* Take into account NAT sequence number mangling */ + receiver_offset = nf_ct_seq_offset(ct, !dir, ack - 1); + ack -= receiver_offset; + sack -= receiver_offset; + + if (sender->td_maxwin == 0) { + /* + * Initialize sender data. + */ + if (tcph->syn) { + tcp_init_sender(sender, receiver, + skb, dataoff, tcph, + end, win); + if (!tcph->ack) + /* Simultaneous open */ + return NFCT_TCP_ACCEPT; + } else { + /* + * We are in the middle of a connection, + * its history is lost for us. + * Let's try to use the data from the packet. + */ + sender->td_end = end; + swin = win << sender->td_scale; + sender->td_maxwin = (swin == 0 ? 1 : swin); + sender->td_maxend = end + sender->td_maxwin; + if (receiver->td_maxwin == 0) { + /* We haven't seen traffic in the other + * direction yet but we have to tweak window + * tracking to pass III and IV until that + * happens. + */ + receiver->td_end = receiver->td_maxend = sack; + } else if (sack == receiver->td_end + 1) { + /* Likely a reply to a keepalive. + * Needed for III. + */ + receiver->td_end++; + } + + } + } else if (tcph->syn && + after(end, sender->td_end) && + (state->state == TCP_CONNTRACK_SYN_SENT || + state->state == TCP_CONNTRACK_SYN_RECV)) { + /* + * RFC 793: "if a TCP is reinitialized ... then it need + * not wait at all; it must only be sure to use sequence + * numbers larger than those recently used." + * + * Re-init state for this direction, just like for the first + * syn(-ack) reply, it might differ in seq, ack or tcp options. + */ + tcp_init_sender(sender, receiver, + skb, dataoff, tcph, + end, win); + + if (dir == IP_CT_DIR_REPLY && !tcph->ack) + return NFCT_TCP_ACCEPT; + } + + if (!(tcph->ack)) { + /* + * If there is no ACK, just pretend it was set and OK. + */ + ack = sack = receiver->td_end; + } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) == + (TCP_FLAG_ACK|TCP_FLAG_RST)) + && (ack == 0)) { + /* + * Broken TCP stacks, that set ACK in RST packets as well + * with zero ack value. + */ + ack = sack = receiver->td_end; + } + + if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT) + /* + * RST sent answering SYN. + */ + seq = end = sender->td_end; + + seq_ok = before(seq, sender->td_maxend + 1); + if (!seq_ok) { + u32 overshot = end - sender->td_maxend + 1; + bool ack_ok; + + ack_ok = after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1); + in_recv_win = receiver->td_maxwin && + after(end, sender->td_end - receiver->td_maxwin - 1); + + if (in_recv_win && + ack_ok && + overshot <= receiver->td_maxwin && + before(sack, receiver->td_end + 1)) { + /* Work around TCPs that send more bytes than allowed by + * the receive window. + * + * If the (marked as invalid) packet is allowed to pass by + * the ruleset and the peer acks this data, then its possible + * all future packets will trigger 'ACK is over upper bound' check. + * + * Thus if only the sequence check fails then do update td_end so + * possible ACK for this data can update internal state. + */ + sender->td_end = end; + sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED; + + return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, + "%u bytes more than expected", overshot); + } + + return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_INVALID, + "SEQ is over upper bound %u (over the window of the receiver)", + sender->td_maxend + 1); + } + + if (!before(sack, receiver->td_end + 1)) + return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_INVALID, + "ACK is over upper bound %u (ACKed data not seen yet)", + receiver->td_end + 1); + + /* Is the ending sequence in the receive window (if available)? */ + in_recv_win = !receiver->td_maxwin || + after(end, sender->td_end - receiver->td_maxwin - 1); + if (!in_recv_win) + return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, + "SEQ is under lower bound %u (already ACKed data retransmitted)", + sender->td_end - receiver->td_maxwin - 1); + if (!after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) + return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, + "ignored ACK under lower bound %u (possible overly delayed)", + receiver->td_end - MAXACKWINDOW(sender) - 1); + + /* Take into account window scaling (RFC 1323). */ + if (!tcph->syn) + win <<= sender->td_scale; + + /* Update sender data. */ + swin = win + (sack - ack); + if (sender->td_maxwin < swin) + sender->td_maxwin = swin; + if (after(end, sender->td_end)) { + sender->td_end = end; + sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED; + } + if (tcph->ack) { + if (!(sender->flags & IP_CT_TCP_FLAG_MAXACK_SET)) { + sender->td_maxack = ack; + sender->flags |= IP_CT_TCP_FLAG_MAXACK_SET; + } else if (after(ack, sender->td_maxack)) { + sender->td_maxack = ack; + } + } + + /* Update receiver data. */ + if (receiver->td_maxwin != 0 && after(end, sender->td_maxend)) + receiver->td_maxwin += end - sender->td_maxend; + if (after(sack + win, receiver->td_maxend - 1)) { + receiver->td_maxend = sack + win; + if (win == 0) + receiver->td_maxend++; + } + if (ack == receiver->td_end) + receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED; + + /* Check retransmissions. */ + if (index == TCP_ACK_SET) { + if (state->last_dir == dir && + state->last_seq == seq && + state->last_ack == ack && + state->last_end == end && + state->last_win == win_raw) { + state->retrans++; + } else { + state->last_dir = dir; + state->last_seq = seq; + state->last_ack = ack; + state->last_end = end; + state->last_win = win_raw; + state->retrans = 0; + } + } + + return NFCT_TCP_ACCEPT; +} + +static void __cold nf_tcp_handle_invalid(struct nf_conn *ct, + enum ip_conntrack_dir dir, + int index, + const struct sk_buff *skb, + const struct nf_hook_state *hook_state) +{ + const unsigned int *timeouts; + const struct nf_tcp_net *tn; + unsigned int timeout; + u32 expires; + + if (!test_bit(IPS_ASSURED_BIT, &ct->status) || + test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status)) + return; + + /* We don't want to have connections hanging around in ESTABLISHED + * state for long time 'just because' conntrack deemed a FIN/RST + * out-of-window. + * + * Shrink the timeout just like when there is unacked data. + * This speeds up eviction of 'dead' connections where the + * connection and conntracks internal state are out of sync. + */ + switch (index) { + case TCP_RST_SET: + case TCP_FIN_SET: + break; + default: + return; + } + + if (ct->proto.tcp.last_dir != dir && + (ct->proto.tcp.last_index == TCP_FIN_SET || + ct->proto.tcp.last_index == TCP_RST_SET)) { + expires = nf_ct_expires(ct); + if (expires < 120 * HZ) + return; + + tn = nf_tcp_pernet(nf_ct_net(ct)); + timeouts = nf_ct_timeout_lookup(ct); + if (!timeouts) + timeouts = tn->timeouts; + + timeout = READ_ONCE(timeouts[TCP_CONNTRACK_UNACK]); + if (expires > timeout) { + nf_ct_l4proto_log_invalid(skb, ct, hook_state, + "packet (index %d, dir %d) response for index %d lower timeout to %u", + index, dir, ct->proto.tcp.last_index, timeout); + + WRITE_ONCE(ct->timeout, timeout + nfct_time_stamp); + } + } else { + ct->proto.tcp.last_index = index; + ct->proto.tcp.last_dir = dir; + } +} + +/* table of valid flag combinations - PUSH, ECE and CWR are always valid */ +static const u8 tcp_valid_flags[(TCPHDR_FIN|TCPHDR_SYN|TCPHDR_RST|TCPHDR_ACK| + TCPHDR_URG) + 1] = +{ + [TCPHDR_SYN] = 1, + [TCPHDR_SYN|TCPHDR_URG] = 1, + [TCPHDR_SYN|TCPHDR_ACK] = 1, + [TCPHDR_RST] = 1, + [TCPHDR_RST|TCPHDR_ACK] = 1, + [TCPHDR_FIN|TCPHDR_ACK] = 1, + [TCPHDR_FIN|TCPHDR_ACK|TCPHDR_URG] = 1, + [TCPHDR_ACK] = 1, + [TCPHDR_ACK|TCPHDR_URG] = 1, +}; + +static void tcp_error_log(const struct sk_buff *skb, + const struct nf_hook_state *state, + const char *msg) +{ + nf_l4proto_log_invalid(skb, state, IPPROTO_TCP, "%s", msg); +} + +/* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c. */ +static bool tcp_error(const struct tcphdr *th, + struct sk_buff *skb, + unsigned int dataoff, + const struct nf_hook_state *state) +{ + unsigned int tcplen = skb->len - dataoff; + u8 tcpflags; + + /* Not whole TCP header or malformed packet */ + if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) { + tcp_error_log(skb, state, "truncated packet"); + return true; + } + + /* Checksum invalid? Ignore. + * We skip checking packets on the outgoing path + * because the checksum is assumed to be correct. + */ + /* FIXME: Source route IP option packets --RR */ + if (state->net->ct.sysctl_checksum && + state->hook == NF_INET_PRE_ROUTING && + nf_checksum(skb, state->hook, dataoff, IPPROTO_TCP, state->pf)) { + tcp_error_log(skb, state, "bad checksum"); + return true; + } + + /* Check TCP flags. */ + tcpflags = (tcp_flag_byte(th) & ~(TCPHDR_ECE|TCPHDR_CWR|TCPHDR_PSH)); + if (!tcp_valid_flags[tcpflags]) { + tcp_error_log(skb, state, "invalid tcp flag combination"); + return true; + } + + return false; +} + +static noinline bool tcp_new(struct nf_conn *ct, const struct sk_buff *skb, + unsigned int dataoff, + const struct tcphdr *th) +{ + enum tcp_conntrack new_state; + struct net *net = nf_ct_net(ct); + const struct nf_tcp_net *tn = nf_tcp_pernet(net); + + /* Don't need lock here: this conntrack not in circulation yet */ + new_state = tcp_conntracks[0][get_conntrack_index(th)][TCP_CONNTRACK_NONE]; + + /* Invalid: delete conntrack */ + if (new_state >= TCP_CONNTRACK_MAX) { + pr_debug("nf_ct_tcp: invalid new deleting.\n"); + return false; + } + + if (new_state == TCP_CONNTRACK_SYN_SENT) { + memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp)); + /* SYN packet */ + ct->proto.tcp.seen[0].td_end = + segment_seq_plus_len(ntohl(th->seq), skb->len, + dataoff, th); + ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window); + if (ct->proto.tcp.seen[0].td_maxwin == 0) + ct->proto.tcp.seen[0].td_maxwin = 1; + ct->proto.tcp.seen[0].td_maxend = + ct->proto.tcp.seen[0].td_end; + + tcp_options(skb, dataoff, th, &ct->proto.tcp.seen[0]); + } else if (tn->tcp_loose == 0) { + /* Don't try to pick up connections. */ + return false; + } else { + memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp)); + /* + * We are in the middle of a connection, + * its history is lost for us. + * Let's try to use the data from the packet. + */ + ct->proto.tcp.seen[0].td_end = + segment_seq_plus_len(ntohl(th->seq), skb->len, + dataoff, th); + ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window); + if (ct->proto.tcp.seen[0].td_maxwin == 0) + ct->proto.tcp.seen[0].td_maxwin = 1; + ct->proto.tcp.seen[0].td_maxend = + ct->proto.tcp.seen[0].td_end + + ct->proto.tcp.seen[0].td_maxwin; + + /* We assume SACK and liberal window checking to handle + * window scaling */ + ct->proto.tcp.seen[0].flags = + ct->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM | + IP_CT_TCP_FLAG_BE_LIBERAL; + } + + /* tcp_packet will set them */ + ct->proto.tcp.last_index = TCP_NONE_SET; + return true; +} + +static bool tcp_can_early_drop(const struct nf_conn *ct) +{ + switch (ct->proto.tcp.state) { + case TCP_CONNTRACK_FIN_WAIT: + case TCP_CONNTRACK_LAST_ACK: + case TCP_CONNTRACK_TIME_WAIT: + case TCP_CONNTRACK_CLOSE: + case TCP_CONNTRACK_CLOSE_WAIT: + return true; + default: + break; + } + + return false; +} + +static void nf_ct_tcp_state_reset(struct ip_ct_tcp_state *state) +{ + state->td_end = 0; + state->td_maxend = 0; + state->td_maxwin = 0; + state->td_maxack = 0; + state->td_scale = 0; + state->flags &= IP_CT_TCP_FLAG_BE_LIBERAL; +} + +/* Returns verdict for packet, or -1 for invalid. */ +int nf_conntrack_tcp_packet(struct nf_conn *ct, + struct sk_buff *skb, + unsigned int dataoff, + enum ip_conntrack_info ctinfo, + const struct nf_hook_state *state) +{ + struct net *net = nf_ct_net(ct); + struct nf_tcp_net *tn = nf_tcp_pernet(net); + struct nf_conntrack_tuple *tuple; + enum tcp_conntrack new_state, old_state; + unsigned int index, *timeouts; + enum nf_ct_tcp_action res; + enum ip_conntrack_dir dir; + const struct tcphdr *th; + struct tcphdr _tcph; + unsigned long timeout; + + th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph); + if (th == NULL) + return -NF_ACCEPT; + + if (tcp_error(th, skb, dataoff, state)) + return -NF_ACCEPT; + + if (!nf_ct_is_confirmed(ct) && !tcp_new(ct, skb, dataoff, th)) + return -NF_ACCEPT; + + spin_lock_bh(&ct->lock); + old_state = ct->proto.tcp.state; + dir = CTINFO2DIR(ctinfo); + index = get_conntrack_index(th); + new_state = tcp_conntracks[dir][index][old_state]; + tuple = &ct->tuplehash[dir].tuple; + + switch (new_state) { + case TCP_CONNTRACK_SYN_SENT: + if (old_state < TCP_CONNTRACK_TIME_WAIT) + break; + /* RFC 1122: "When a connection is closed actively, + * it MUST linger in TIME-WAIT state for a time 2xMSL + * (Maximum Segment Lifetime). However, it MAY accept + * a new SYN from the remote TCP to reopen the connection + * directly from TIME-WAIT state, if..." + * We ignore the conditions because we are in the + * TIME-WAIT state anyway. + * + * Handle aborted connections: we and the server + * think there is an existing connection but the client + * aborts it and starts a new one. + */ + if (((ct->proto.tcp.seen[dir].flags + | ct->proto.tcp.seen[!dir].flags) + & IP_CT_TCP_FLAG_CLOSE_INIT) + || (ct->proto.tcp.last_dir == dir + && ct->proto.tcp.last_index == TCP_RST_SET)) { + /* Attempt to reopen a closed/aborted connection. + * Delete this connection and look up again. */ + spin_unlock_bh(&ct->lock); + + /* Only repeat if we can actually remove the timer. + * Destruction may already be in progress in process + * context and we must give it a chance to terminate. + */ + if (nf_ct_kill(ct)) + return -NF_REPEAT; + return NF_DROP; + } + fallthrough; + case TCP_CONNTRACK_IGNORE: + /* Ignored packets: + * + * Our connection entry may be out of sync, so ignore + * packets which may signal the real connection between + * the client and the server. + * + * a) SYN in ORIGINAL + * b) SYN/ACK in REPLY + * c) ACK in reply direction after initial SYN in original. + * + * If the ignored packet is invalid, the receiver will send + * a RST we'll catch below. + */ + if (index == TCP_SYNACK_SET + && ct->proto.tcp.last_index == TCP_SYN_SET + && ct->proto.tcp.last_dir != dir + && ntohl(th->ack_seq) == ct->proto.tcp.last_end) { + /* b) This SYN/ACK acknowledges a SYN that we earlier + * ignored as invalid. This means that the client and + * the server are both in sync, while the firewall is + * not. We get in sync from the previously annotated + * values. + */ + old_state = TCP_CONNTRACK_SYN_SENT; + new_state = TCP_CONNTRACK_SYN_RECV; + ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end = + ct->proto.tcp.last_end; + ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend = + ct->proto.tcp.last_end; + ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin = + ct->proto.tcp.last_win == 0 ? + 1 : ct->proto.tcp.last_win; + ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale = + ct->proto.tcp.last_wscale; + ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK; + ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags = + ct->proto.tcp.last_flags; + nf_ct_tcp_state_reset(&ct->proto.tcp.seen[dir]); + break; + } + ct->proto.tcp.last_index = index; + ct->proto.tcp.last_dir = dir; + ct->proto.tcp.last_seq = ntohl(th->seq); + ct->proto.tcp.last_end = + segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th); + ct->proto.tcp.last_win = ntohs(th->window); + + /* a) This is a SYN in ORIGINAL. The client and the server + * may be in sync but we are not. In that case, we annotate + * the TCP options and let the packet go through. If it is a + * valid SYN packet, the server will reply with a SYN/ACK, and + * then we'll get in sync. Otherwise, the server potentially + * responds with a challenge ACK if implementing RFC5961. + */ + if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) { + struct ip_ct_tcp_state seen = {}; + + ct->proto.tcp.last_flags = + ct->proto.tcp.last_wscale = 0; + tcp_options(skb, dataoff, th, &seen); + if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) { + ct->proto.tcp.last_flags |= + IP_CT_TCP_FLAG_WINDOW_SCALE; + ct->proto.tcp.last_wscale = seen.td_scale; + } + if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) { + ct->proto.tcp.last_flags |= + IP_CT_TCP_FLAG_SACK_PERM; + } + /* Mark the potential for RFC5961 challenge ACK, + * this pose a special problem for LAST_ACK state + * as ACK is intrepretated as ACKing last FIN. + */ + if (old_state == TCP_CONNTRACK_LAST_ACK) + ct->proto.tcp.last_flags |= + IP_CT_EXP_CHALLENGE_ACK; + } + + /* possible challenge ack reply to syn */ + if (old_state == TCP_CONNTRACK_SYN_SENT && + index == TCP_ACK_SET && + dir == IP_CT_DIR_REPLY) + ct->proto.tcp.last_ack = ntohl(th->ack_seq); + + spin_unlock_bh(&ct->lock); + nf_ct_l4proto_log_invalid(skb, ct, state, + "packet (index %d) in dir %d ignored, state %s", + index, dir, + tcp_conntrack_names[old_state]); + return NF_ACCEPT; + case TCP_CONNTRACK_MAX: + /* Special case for SYN proxy: when the SYN to the server or + * the SYN/ACK from the server is lost, the client may transmit + * a keep-alive packet while in SYN_SENT state. This needs to + * be associated with the original conntrack entry in order to + * generate a new SYN with the correct sequence number. + */ + if (nfct_synproxy(ct) && old_state == TCP_CONNTRACK_SYN_SENT && + index == TCP_ACK_SET && dir == IP_CT_DIR_ORIGINAL && + ct->proto.tcp.last_dir == IP_CT_DIR_ORIGINAL && + ct->proto.tcp.seen[dir].td_end - 1 == ntohl(th->seq)) { + pr_debug("nf_ct_tcp: SYN proxy client keep alive\n"); + spin_unlock_bh(&ct->lock); + return NF_ACCEPT; + } + + /* Invalid packet */ + spin_unlock_bh(&ct->lock); + nf_ct_l4proto_log_invalid(skb, ct, state, + "packet (index %d) in dir %d invalid, state %s", + index, dir, + tcp_conntrack_names[old_state]); + return -NF_ACCEPT; + case TCP_CONNTRACK_TIME_WAIT: + /* RFC5961 compliance cause stack to send "challenge-ACK" + * e.g. in response to spurious SYNs. Conntrack MUST + * not believe this ACK is acking last FIN. + */ + if (old_state == TCP_CONNTRACK_LAST_ACK && + index == TCP_ACK_SET && + ct->proto.tcp.last_dir != dir && + ct->proto.tcp.last_index == TCP_SYN_SET && + (ct->proto.tcp.last_flags & IP_CT_EXP_CHALLENGE_ACK)) { + /* Detected RFC5961 challenge ACK */ + ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK; + spin_unlock_bh(&ct->lock); + nf_ct_l4proto_log_invalid(skb, ct, state, "challenge-ack ignored"); + return NF_ACCEPT; /* Don't change state */ + } + break; + case TCP_CONNTRACK_SYN_SENT2: + /* tcp_conntracks table is not smart enough to handle + * simultaneous open. + */ + ct->proto.tcp.last_flags |= IP_CT_TCP_SIMULTANEOUS_OPEN; + break; + case TCP_CONNTRACK_SYN_RECV: + if (dir == IP_CT_DIR_REPLY && index == TCP_ACK_SET && + ct->proto.tcp.last_flags & IP_CT_TCP_SIMULTANEOUS_OPEN) + new_state = TCP_CONNTRACK_ESTABLISHED; + break; + case TCP_CONNTRACK_CLOSE: + if (index != TCP_RST_SET) + break; + + /* If we are closing, tuple might have been re-used already. + * last_index, last_ack, and all other ct fields used for + * sequence/window validation are outdated in that case. + * + * As the conntrack can already be expired by GC under pressure, + * just skip validation checks. + */ + if (tcp_can_early_drop(ct)) + goto in_window; + + /* td_maxack might be outdated if we let a SYN through earlier */ + if ((ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET) && + ct->proto.tcp.last_index != TCP_SYN_SET) { + u32 seq = ntohl(th->seq); + + /* If we are not in established state and SEQ=0 this is most + * likely an answer to a SYN we let go through above (last_index + * can be updated due to out-of-order ACKs). + */ + if (seq == 0 && !nf_conntrack_tcp_established(ct)) + break; + + if (before(seq, ct->proto.tcp.seen[!dir].td_maxack) && + !tn->tcp_ignore_invalid_rst) { + /* Invalid RST */ + spin_unlock_bh(&ct->lock); + nf_ct_l4proto_log_invalid(skb, ct, state, "invalid rst"); + return -NF_ACCEPT; + } + + if (!nf_conntrack_tcp_established(ct) || + seq == ct->proto.tcp.seen[!dir].td_maxack) + break; + + /* Check if rst is part of train, such as + * foo:80 > bar:4379: P, 235946583:235946602(19) ack 42 + * foo:80 > bar:4379: R, 235946602:235946602(0) ack 42 + */ + if (ct->proto.tcp.last_index == TCP_ACK_SET && + ct->proto.tcp.last_dir == dir && + seq == ct->proto.tcp.last_end) + break; + + /* ... RST sequence number doesn't match exactly, keep + * established state to allow a possible challenge ACK. + */ + new_state = old_state; + } + if (((test_bit(IPS_SEEN_REPLY_BIT, &ct->status) + && ct->proto.tcp.last_index == TCP_SYN_SET) + || (!test_bit(IPS_ASSURED_BIT, &ct->status) + && ct->proto.tcp.last_index == TCP_ACK_SET)) + && ntohl(th->ack_seq) == ct->proto.tcp.last_end) { + /* RST sent to invalid SYN or ACK we had let through + * at a) and c) above: + * + * a) SYN was in window then + * c) we hold a half-open connection. + * + * Delete our connection entry. + * We skip window checking, because packet might ACK + * segments we ignored. */ + goto in_window; + } + + /* Reset in response to a challenge-ack we let through earlier */ + if (old_state == TCP_CONNTRACK_SYN_SENT && + ct->proto.tcp.last_index == TCP_ACK_SET && + ct->proto.tcp.last_dir == IP_CT_DIR_REPLY && + ntohl(th->seq) == ct->proto.tcp.last_ack) + goto in_window; + + break; + default: + /* Keep compilers happy. */ + break; + } + + res = tcp_in_window(ct, dir, index, + skb, dataoff, th, state); + switch (res) { + case NFCT_TCP_IGNORE: + spin_unlock_bh(&ct->lock); + return NF_ACCEPT; + case NFCT_TCP_INVALID: + nf_tcp_handle_invalid(ct, dir, index, skb, state); + spin_unlock_bh(&ct->lock); + return -NF_ACCEPT; + case NFCT_TCP_ACCEPT: + break; + } + in_window: + /* From now on we have got in-window packets */ + ct->proto.tcp.last_index = index; + ct->proto.tcp.last_dir = dir; + + pr_debug("tcp_conntracks: "); + nf_ct_dump_tuple(tuple); + pr_debug("syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n", + (th->syn ? 1 : 0), (th->ack ? 1 : 0), + (th->fin ? 1 : 0), (th->rst ? 1 : 0), + old_state, new_state); + + ct->proto.tcp.state = new_state; + if (old_state != new_state + && new_state == TCP_CONNTRACK_FIN_WAIT) + ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT; + + timeouts = nf_ct_timeout_lookup(ct); + if (!timeouts) + timeouts = tn->timeouts; + + if (ct->proto.tcp.retrans >= tn->tcp_max_retrans && + timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS]) + timeout = timeouts[TCP_CONNTRACK_RETRANS]; + else if (unlikely(index == TCP_RST_SET)) + timeout = timeouts[TCP_CONNTRACK_CLOSE]; + else if ((ct->proto.tcp.seen[0].flags | ct->proto.tcp.seen[1].flags) & + IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED && + timeouts[new_state] > timeouts[TCP_CONNTRACK_UNACK]) + timeout = timeouts[TCP_CONNTRACK_UNACK]; + else if (ct->proto.tcp.last_win == 0 && + timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS]) + timeout = timeouts[TCP_CONNTRACK_RETRANS]; + else + timeout = timeouts[new_state]; + spin_unlock_bh(&ct->lock); + + if (new_state != old_state) + nf_conntrack_event_cache(IPCT_PROTOINFO, ct); + + if (!test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) { + /* If only reply is a RST, we can consider ourselves not to + have an established connection: this is a fairly common + problem case, so we can delete the conntrack + immediately. --RR */ + if (th->rst) { + nf_ct_kill_acct(ct, ctinfo, skb); + return NF_ACCEPT; + } + + if (index == TCP_SYN_SET && old_state == TCP_CONNTRACK_SYN_SENT) { + /* do not renew timeout on SYN retransmit. + * + * Else port reuse by client or NAT middlebox can keep + * entry alive indefinitely (including nat info). + */ + return NF_ACCEPT; + } + + /* ESTABLISHED without SEEN_REPLY, i.e. mid-connection + * pickup with loose=1. Avoid large ESTABLISHED timeout. + */ + if (new_state == TCP_CONNTRACK_ESTABLISHED && + timeout > timeouts[TCP_CONNTRACK_UNACK]) + timeout = timeouts[TCP_CONNTRACK_UNACK]; + } else if (!test_bit(IPS_ASSURED_BIT, &ct->status) + && (old_state == TCP_CONNTRACK_SYN_RECV + || old_state == TCP_CONNTRACK_ESTABLISHED) + && new_state == TCP_CONNTRACK_ESTABLISHED) { + /* Set ASSURED if we see valid ack in ESTABLISHED + after SYN_RECV or a valid answer for a picked up + connection. */ + set_bit(IPS_ASSURED_BIT, &ct->status); + nf_conntrack_event_cache(IPCT_ASSURED, ct); + } + nf_ct_refresh_acct(ct, ctinfo, skb, timeout); + + return NF_ACCEPT; +} + +#if IS_ENABLED(CONFIG_NF_CT_NETLINK) + +#include <linux/netfilter/nfnetlink.h> +#include <linux/netfilter/nfnetlink_conntrack.h> + +static int tcp_to_nlattr(struct sk_buff *skb, struct nlattr *nla, + struct nf_conn *ct, bool destroy) +{ + struct nlattr *nest_parms; + struct nf_ct_tcp_flags tmp = {}; + + spin_lock_bh(&ct->lock); + nest_parms = nla_nest_start(skb, CTA_PROTOINFO_TCP); + if (!nest_parms) + goto nla_put_failure; + + if (nla_put_u8(skb, CTA_PROTOINFO_TCP_STATE, ct->proto.tcp.state)) + goto nla_put_failure; + + if (destroy) + goto skip_state; + + if (nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL, + ct->proto.tcp.seen[0].td_scale) || + nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY, + ct->proto.tcp.seen[1].td_scale)) + goto nla_put_failure; + + tmp.flags = ct->proto.tcp.seen[0].flags; + if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_ORIGINAL, + sizeof(struct nf_ct_tcp_flags), &tmp)) + goto nla_put_failure; + + tmp.flags = ct->proto.tcp.seen[1].flags; + if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_REPLY, + sizeof(struct nf_ct_tcp_flags), &tmp)) + goto nla_put_failure; +skip_state: + spin_unlock_bh(&ct->lock); + nla_nest_end(skb, nest_parms); + + return 0; + +nla_put_failure: + spin_unlock_bh(&ct->lock); + return -1; +} + +static const struct nla_policy tcp_nla_policy[CTA_PROTOINFO_TCP_MAX+1] = { + [CTA_PROTOINFO_TCP_STATE] = { .type = NLA_U8 }, + [CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] = { .type = NLA_U8 }, + [CTA_PROTOINFO_TCP_WSCALE_REPLY] = { .type = NLA_U8 }, + [CTA_PROTOINFO_TCP_FLAGS_ORIGINAL] = { .len = sizeof(struct nf_ct_tcp_flags) }, + [CTA_PROTOINFO_TCP_FLAGS_REPLY] = { .len = sizeof(struct nf_ct_tcp_flags) }, +}; + +#define TCP_NLATTR_SIZE ( \ + NLA_ALIGN(NLA_HDRLEN + 1) + \ + NLA_ALIGN(NLA_HDRLEN + 1) + \ + NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)) + \ + NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags))) + +static int nlattr_to_tcp(struct nlattr *cda[], struct nf_conn *ct) +{ + struct nlattr *pattr = cda[CTA_PROTOINFO_TCP]; + struct nlattr *tb[CTA_PROTOINFO_TCP_MAX+1]; + int err; + + /* updates could not contain anything about the private + * protocol info, in that case skip the parsing */ + if (!pattr) + return 0; + + err = nla_parse_nested_deprecated(tb, CTA_PROTOINFO_TCP_MAX, pattr, + tcp_nla_policy, NULL); + if (err < 0) + return err; + + if (tb[CTA_PROTOINFO_TCP_STATE] && + nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]) >= TCP_CONNTRACK_MAX) + return -EINVAL; + + spin_lock_bh(&ct->lock); + if (tb[CTA_PROTOINFO_TCP_STATE]) + ct->proto.tcp.state = nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]); + + if (tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]) { + struct nf_ct_tcp_flags *attr = + nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]); + ct->proto.tcp.seen[0].flags &= ~attr->mask; + ct->proto.tcp.seen[0].flags |= attr->flags & attr->mask; + } + + if (tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]) { + struct nf_ct_tcp_flags *attr = + nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]); + ct->proto.tcp.seen[1].flags &= ~attr->mask; + ct->proto.tcp.seen[1].flags |= attr->flags & attr->mask; + } + + if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] && + tb[CTA_PROTOINFO_TCP_WSCALE_REPLY] && + ct->proto.tcp.seen[0].flags & IP_CT_TCP_FLAG_WINDOW_SCALE && + ct->proto.tcp.seen[1].flags & IP_CT_TCP_FLAG_WINDOW_SCALE) { + ct->proto.tcp.seen[0].td_scale = + nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL]); + ct->proto.tcp.seen[1].td_scale = + nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY]); + } + spin_unlock_bh(&ct->lock); + + return 0; +} + +static unsigned int tcp_nlattr_tuple_size(void) +{ + static unsigned int size __read_mostly; + + if (!size) + size = nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1); + + return size; +} +#endif + +#ifdef CONFIG_NF_CONNTRACK_TIMEOUT + +#include <linux/netfilter/nfnetlink.h> +#include <linux/netfilter/nfnetlink_cttimeout.h> + +static int tcp_timeout_nlattr_to_obj(struct nlattr *tb[], + struct net *net, void *data) +{ + struct nf_tcp_net *tn = nf_tcp_pernet(net); + unsigned int *timeouts = data; + int i; + + if (!timeouts) + timeouts = tn->timeouts; + /* set default TCP timeouts. */ + for (i=0; i<TCP_CONNTRACK_TIMEOUT_MAX; i++) + timeouts[i] = tn->timeouts[i]; + + if (tb[CTA_TIMEOUT_TCP_SYN_SENT]) { + timeouts[TCP_CONNTRACK_SYN_SENT] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT]))*HZ; + } + + if (tb[CTA_TIMEOUT_TCP_SYN_RECV]) { + timeouts[TCP_CONNTRACK_SYN_RECV] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_RECV]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_ESTABLISHED]) { + timeouts[TCP_CONNTRACK_ESTABLISHED] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_ESTABLISHED]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_FIN_WAIT]) { + timeouts[TCP_CONNTRACK_FIN_WAIT] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_FIN_WAIT]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]) { + timeouts[TCP_CONNTRACK_CLOSE_WAIT] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_LAST_ACK]) { + timeouts[TCP_CONNTRACK_LAST_ACK] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_LAST_ACK]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_TIME_WAIT]) { + timeouts[TCP_CONNTRACK_TIME_WAIT] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_TIME_WAIT]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_CLOSE]) { + timeouts[TCP_CONNTRACK_CLOSE] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_SYN_SENT2]) { + timeouts[TCP_CONNTRACK_SYN_SENT2] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT2]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_RETRANS]) { + timeouts[TCP_CONNTRACK_RETRANS] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_RETRANS]))*HZ; + } + if (tb[CTA_TIMEOUT_TCP_UNACK]) { + timeouts[TCP_CONNTRACK_UNACK] = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_UNACK]))*HZ; + } + + timeouts[CTA_TIMEOUT_TCP_UNSPEC] = timeouts[CTA_TIMEOUT_TCP_SYN_SENT]; + return 0; +} + +static int +tcp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data) +{ + const unsigned int *timeouts = data; + + if (nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT, + htonl(timeouts[TCP_CONNTRACK_SYN_SENT] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_RECV, + htonl(timeouts[TCP_CONNTRACK_SYN_RECV] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_ESTABLISHED, + htonl(timeouts[TCP_CONNTRACK_ESTABLISHED] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_FIN_WAIT, + htonl(timeouts[TCP_CONNTRACK_FIN_WAIT] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE_WAIT, + htonl(timeouts[TCP_CONNTRACK_CLOSE_WAIT] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_LAST_ACK, + htonl(timeouts[TCP_CONNTRACK_LAST_ACK] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_TIME_WAIT, + htonl(timeouts[TCP_CONNTRACK_TIME_WAIT] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE, + htonl(timeouts[TCP_CONNTRACK_CLOSE] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT2, + htonl(timeouts[TCP_CONNTRACK_SYN_SENT2] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_RETRANS, + htonl(timeouts[TCP_CONNTRACK_RETRANS] / HZ)) || + nla_put_be32(skb, CTA_TIMEOUT_TCP_UNACK, + htonl(timeouts[TCP_CONNTRACK_UNACK] / HZ))) + goto nla_put_failure; + return 0; + +nla_put_failure: + return -ENOSPC; +} + +static const struct nla_policy tcp_timeout_nla_policy[CTA_TIMEOUT_TCP_MAX+1] = { + [CTA_TIMEOUT_TCP_SYN_SENT] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_SYN_RECV] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_ESTABLISHED] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_FIN_WAIT] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_CLOSE_WAIT] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_LAST_ACK] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_TIME_WAIT] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_CLOSE] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_SYN_SENT2] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_RETRANS] = { .type = NLA_U32 }, + [CTA_TIMEOUT_TCP_UNACK] = { .type = NLA_U32 }, +}; +#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ + +void nf_conntrack_tcp_init_net(struct net *net) +{ + struct nf_tcp_net *tn = nf_tcp_pernet(net); + int i; + + for (i = 0; i < TCP_CONNTRACK_TIMEOUT_MAX; i++) + tn->timeouts[i] = tcp_timeouts[i]; + + /* timeouts[0] is unused, make it same as SYN_SENT so + * ->timeouts[0] contains 'new' timeout, like udp or icmp. + */ + tn->timeouts[0] = tcp_timeouts[TCP_CONNTRACK_SYN_SENT]; + + /* If it is set to zero, we disable picking up already established + * connections. + */ + tn->tcp_loose = 1; + + /* "Be conservative in what you do, + * be liberal in what you accept from others." + * If it's non-zero, we mark only out of window RST segments as INVALID. + */ + tn->tcp_be_liberal = 0; + + /* If it's non-zero, we turn off RST sequence number check */ + tn->tcp_ignore_invalid_rst = 0; + + /* Max number of the retransmitted packets without receiving an (acceptable) + * ACK from the destination. If this number is reached, a shorter timer + * will be started. + */ + tn->tcp_max_retrans = 3; + +#if IS_ENABLED(CONFIG_NF_FLOW_TABLE) + tn->offload_timeout = 30 * HZ; +#endif +} + +const struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp = +{ + .l4proto = IPPROTO_TCP, +#ifdef CONFIG_NF_CONNTRACK_PROCFS + .print_conntrack = tcp_print_conntrack, +#endif + .can_early_drop = tcp_can_early_drop, +#if IS_ENABLED(CONFIG_NF_CT_NETLINK) + .to_nlattr = tcp_to_nlattr, + .from_nlattr = nlattr_to_tcp, + .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr, + .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple, + .nlattr_tuple_size = tcp_nlattr_tuple_size, + .nlattr_size = TCP_NLATTR_SIZE, + .nla_policy = nf_ct_port_nla_policy, +#endif +#ifdef CONFIG_NF_CONNTRACK_TIMEOUT + .ctnl_timeout = { + .nlattr_to_obj = tcp_timeout_nlattr_to_obj, + .obj_to_nlattr = tcp_timeout_obj_to_nlattr, + .nlattr_max = CTA_TIMEOUT_TCP_MAX, + .obj_size = sizeof(unsigned int) * + TCP_CONNTRACK_TIMEOUT_MAX, + .nla_policy = tcp_timeout_nla_policy, + }, +#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ +}; |