diff options
Diffstat (limited to '')
| -rw-r--r-- | net/mptcp/options.c | 1138 |
1 files changed, 1138 insertions, 0 deletions
diff --git a/net/mptcp/options.c b/net/mptcp/options.c new file mode 100644 index 000000000..c389d7e47 --- /dev/null +++ b/net/mptcp/options.c @@ -0,0 +1,1138 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Multipath TCP + * + * Copyright (c) 2017 - 2019, Intel Corporation. + */ + +#define pr_fmt(fmt) "MPTCP: " fmt + +#include <linux/kernel.h> +#include <crypto/sha.h> +#include <net/tcp.h> +#include <net/mptcp.h> +#include "protocol.h" +#include "mib.h" + +static bool mptcp_cap_flag_sha256(u8 flags) +{ + return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256; +} + +static void mptcp_parse_option(const struct sk_buff *skb, + const unsigned char *ptr, int opsize, + struct mptcp_options_received *mp_opt) +{ + u8 subtype = *ptr >> 4; + int expected_opsize; + u8 version; + u8 flags; + + switch (subtype) { + case MPTCPOPT_MP_CAPABLE: + /* strict size checking */ + if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) { + if (skb->len > tcp_hdr(skb)->doff << 2) + expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA; + else + expected_opsize = TCPOLEN_MPTCP_MPC_ACK; + } else { + if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) + expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK; + else + expected_opsize = TCPOLEN_MPTCP_MPC_SYN; + } + if (opsize != expected_opsize) + break; + + /* try to be gentle vs future versions on the initial syn */ + version = *ptr++ & MPTCP_VERSION_MASK; + if (opsize != TCPOLEN_MPTCP_MPC_SYN) { + if (version != MPTCP_SUPPORTED_VERSION) + break; + } else if (version < MPTCP_SUPPORTED_VERSION) { + break; + } + + flags = *ptr++; + if (!mptcp_cap_flag_sha256(flags) || + (flags & MPTCP_CAP_EXTENSIBILITY)) + break; + + /* RFC 6824, Section 3.1: + * "For the Checksum Required bit (labeled "A"), if either + * host requires the use of checksums, checksums MUST be used. + * In other words, the only way for checksums not to be used + * is if both hosts in their SYNs set A=0." + * + * Section 3.3.0: + * "If a checksum is not present when its use has been + * negotiated, the receiver MUST close the subflow with a RST as + * it is considered broken." + * + * We don't implement DSS checksum - fall back to TCP. + */ + if (flags & MPTCP_CAP_CHECKSUM_REQD) + break; + + mp_opt->mp_capable = 1; + if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) { + mp_opt->sndr_key = get_unaligned_be64(ptr); + ptr += 8; + } + if (opsize >= TCPOLEN_MPTCP_MPC_ACK) { + mp_opt->rcvr_key = get_unaligned_be64(ptr); + ptr += 8; + } + if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) { + /* Section 3.1.: + * "the data parameters in a MP_CAPABLE are semantically + * equivalent to those in a DSS option and can be used + * interchangeably." + */ + mp_opt->dss = 1; + mp_opt->use_map = 1; + mp_opt->mpc_map = 1; + mp_opt->use_ack = 0; + mp_opt->data_len = get_unaligned_be16(ptr); + ptr += 2; + } + pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d", + version, flags, opsize, mp_opt->sndr_key, + mp_opt->rcvr_key, mp_opt->data_len); + break; + + case MPTCPOPT_MP_JOIN: + mp_opt->mp_join = 1; + if (opsize == TCPOLEN_MPTCP_MPJ_SYN) { + mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP; + mp_opt->join_id = *ptr++; + mp_opt->token = get_unaligned_be32(ptr); + ptr += 4; + mp_opt->nonce = get_unaligned_be32(ptr); + ptr += 4; + pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u", + mp_opt->backup, mp_opt->join_id, + mp_opt->token, mp_opt->nonce); + } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) { + mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP; + mp_opt->join_id = *ptr++; + mp_opt->thmac = get_unaligned_be64(ptr); + ptr += 8; + mp_opt->nonce = get_unaligned_be32(ptr); + ptr += 4; + pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u", + mp_opt->backup, mp_opt->join_id, + mp_opt->thmac, mp_opt->nonce); + } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) { + ptr += 2; + memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN); + pr_debug("MP_JOIN hmac"); + } else { + mp_opt->mp_join = 0; + } + break; + + case MPTCPOPT_DSS: + pr_debug("DSS"); + ptr++; + + /* we must clear 'mpc_map' be able to detect MP_CAPABLE + * map vs DSS map in mptcp_incoming_options(), and reconstruct + * map info accordingly + */ + mp_opt->mpc_map = 0; + flags = (*ptr++) & MPTCP_DSS_FLAG_MASK; + mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0; + mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0; + mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0; + mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0; + mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK); + + pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d", + mp_opt->data_fin, mp_opt->dsn64, + mp_opt->use_map, mp_opt->ack64, + mp_opt->use_ack); + + expected_opsize = TCPOLEN_MPTCP_DSS_BASE; + + if (mp_opt->use_ack) { + if (mp_opt->ack64) + expected_opsize += TCPOLEN_MPTCP_DSS_ACK64; + else + expected_opsize += TCPOLEN_MPTCP_DSS_ACK32; + } + + if (mp_opt->use_map) { + if (mp_opt->dsn64) + expected_opsize += TCPOLEN_MPTCP_DSS_MAP64; + else + expected_opsize += TCPOLEN_MPTCP_DSS_MAP32; + } + + /* RFC 6824, Section 3.3: + * If a checksum is present, but its use had + * not been negotiated in the MP_CAPABLE handshake, + * the checksum field MUST be ignored. + */ + if (opsize != expected_opsize && + opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) + break; + + mp_opt->dss = 1; + + if (mp_opt->use_ack) { + if (mp_opt->ack64) { + mp_opt->data_ack = get_unaligned_be64(ptr); + ptr += 8; + } else { + mp_opt->data_ack = get_unaligned_be32(ptr); + ptr += 4; + } + + pr_debug("data_ack=%llu", mp_opt->data_ack); + } + + if (mp_opt->use_map) { + if (mp_opt->dsn64) { + mp_opt->data_seq = get_unaligned_be64(ptr); + ptr += 8; + } else { + mp_opt->data_seq = get_unaligned_be32(ptr); + ptr += 4; + } + + mp_opt->subflow_seq = get_unaligned_be32(ptr); + ptr += 4; + + mp_opt->data_len = get_unaligned_be16(ptr); + ptr += 2; + + pr_debug("data_seq=%llu subflow_seq=%u data_len=%u", + mp_opt->data_seq, mp_opt->subflow_seq, + mp_opt->data_len); + } + + break; + + case MPTCPOPT_ADD_ADDR: + mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO; + if (!mp_opt->echo) { + if (opsize == TCPOLEN_MPTCP_ADD_ADDR || + opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT) + mp_opt->family = MPTCP_ADDR_IPVERSION_4; +#if IS_ENABLED(CONFIG_MPTCP_IPV6) + else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 || + opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT) + mp_opt->family = MPTCP_ADDR_IPVERSION_6; +#endif + else + break; + } else { + if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE || + opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) + mp_opt->family = MPTCP_ADDR_IPVERSION_4; +#if IS_ENABLED(CONFIG_MPTCP_IPV6) + else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE || + opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) + mp_opt->family = MPTCP_ADDR_IPVERSION_6; +#endif + else + break; + } + + mp_opt->add_addr = 1; + mp_opt->addr_id = *ptr++; + pr_debug("ADD_ADDR: id=%d, echo=%d", mp_opt->addr_id, mp_opt->echo); + if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) { + memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4); + ptr += 4; + if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT || + opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) { + mp_opt->port = get_unaligned_be16(ptr); + ptr += 2; + } + } +#if IS_ENABLED(CONFIG_MPTCP_IPV6) + else { + memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16); + ptr += 16; + if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT || + opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) { + mp_opt->port = get_unaligned_be16(ptr); + ptr += 2; + } + } +#endif + if (!mp_opt->echo) { + mp_opt->ahmac = get_unaligned_be64(ptr); + ptr += 8; + } + break; + + case MPTCPOPT_RM_ADDR: + if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE) + break; + + ptr++; + + mp_opt->rm_addr = 1; + mp_opt->rm_id = *ptr++; + pr_debug("RM_ADDR: id=%d", mp_opt->rm_id); + break; + + default: + break; + } +} + +void mptcp_get_options(const struct sk_buff *skb, + struct mptcp_options_received *mp_opt) +{ + const struct tcphdr *th = tcp_hdr(skb); + const unsigned char *ptr; + int length; + + /* initialize option status */ + mp_opt->mp_capable = 0; + mp_opt->mp_join = 0; + mp_opt->add_addr = 0; + mp_opt->ahmac = 0; + mp_opt->port = 0; + mp_opt->rm_addr = 0; + mp_opt->dss = 0; + + length = (th->doff * 4) - sizeof(struct tcphdr); + ptr = (const unsigned char *)(th + 1); + + 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_MPTCP) + mptcp_parse_option(skb, ptr, opsize, mp_opt); + ptr += opsize - 2; + length -= opsize; + } + } +} + +bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb, + unsigned int *size, struct mptcp_out_options *opts) +{ + struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); + + /* we will use snd_isn to detect first pkt [re]transmission + * in mptcp_established_options_mp() + */ + subflow->snd_isn = TCP_SKB_CB(skb)->end_seq; + if (subflow->request_mptcp) { + opts->suboptions = OPTION_MPTCP_MPC_SYN; + *size = TCPOLEN_MPTCP_MPC_SYN; + return true; + } else if (subflow->request_join) { + pr_debug("remote_token=%u, nonce=%u", subflow->remote_token, + subflow->local_nonce); + opts->suboptions = OPTION_MPTCP_MPJ_SYN; + opts->join_id = subflow->local_id; + opts->token = subflow->remote_token; + opts->nonce = subflow->local_nonce; + opts->backup = subflow->request_bkup; + *size = TCPOLEN_MPTCP_MPJ_SYN; + return true; + } + return false; +} + +/* MP_JOIN client subflow must wait for 4th ack before sending any data: + * TCP can't schedule delack timer before the subflow is fully established. + * MPTCP uses the delack timer to do 3rd ack retransmissions + */ +static void schedule_3rdack_retransmission(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + unsigned long timeout; + + /* reschedule with a timeout above RTT, as we must look only for drop */ + if (tp->srtt_us) + timeout = usecs_to_jiffies(tp->srtt_us >> (3 - 1)); + else + timeout = TCP_TIMEOUT_INIT; + timeout += jiffies; + + WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER); + icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; + icsk->icsk_ack.timeout = timeout; + sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); +} + +static void clear_3rdack_retransmission(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + + sk_stop_timer(sk, &icsk->icsk_delack_timer); + icsk->icsk_ack.timeout = 0; + icsk->icsk_ack.ato = 0; + icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER); +} + +static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb, + unsigned int *size, + unsigned int remaining, + struct mptcp_out_options *opts) +{ + struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); + struct mptcp_ext *mpext; + unsigned int data_len; + + /* When skb is not available, we better over-estimate the emitted + * options len. A full DSS option (28 bytes) is longer than + * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so + * tell the caller to defer the estimate to + * mptcp_established_options_dss(), which will reserve enough space. + */ + if (!skb) + return false; + + /* MPC/MPJ needed only on 3rd ack packet */ + if (subflow->fully_established || + subflow->snd_isn != TCP_SKB_CB(skb)->seq) + return false; + + if (subflow->mp_capable) { + mpext = mptcp_get_ext(skb); + data_len = mpext ? mpext->data_len : 0; + + /* we will check ext_copy.data_len in mptcp_write_options() to + * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and + * TCPOLEN_MPTCP_MPC_ACK + */ + opts->ext_copy.data_len = data_len; + opts->suboptions = OPTION_MPTCP_MPC_ACK; + opts->sndr_key = subflow->local_key; + opts->rcvr_key = subflow->remote_key; + + /* Section 3.1. + * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK + * packets that start the first subflow of an MPTCP connection, + * as well as the first packet that carries data + */ + if (data_len > 0) + *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4); + else + *size = TCPOLEN_MPTCP_MPC_ACK; + + pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d", + subflow, subflow->local_key, subflow->remote_key, + data_len); + + return true; + } else if (subflow->mp_join) { + opts->suboptions = OPTION_MPTCP_MPJ_ACK; + memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN); + *size = TCPOLEN_MPTCP_MPJ_ACK; + pr_debug("subflow=%p", subflow); + + schedule_3rdack_retransmission(sk); + return true; + } + return false; +} + +static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow, + struct sk_buff *skb, struct mptcp_ext *ext) +{ + /* The write_seq value has already been incremented, so the actual + * sequence number for the DATA_FIN is one less. + */ + u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1; + + if (!ext->use_map || !skb->len) { + /* RFC6824 requires a DSS mapping with specific values + * if DATA_FIN is set but no data payload is mapped + */ + ext->data_fin = 1; + ext->use_map = 1; + ext->dsn64 = 1; + ext->data_seq = data_fin_tx_seq; + ext->subflow_seq = 0; + ext->data_len = 1; + } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) { + /* If there's an existing DSS mapping and it is the + * final mapping, DATA_FIN consumes 1 additional byte of + * mapping space. + */ + ext->data_fin = 1; + ext->data_len++; + } +} + +static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb, + unsigned int *size, + unsigned int remaining, + struct mptcp_out_options *opts) +{ + struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); + struct mptcp_sock *msk = mptcp_sk(subflow->conn); + unsigned int dss_size = 0; + u64 snd_data_fin_enable; + struct mptcp_ext *mpext; + unsigned int ack_size; + bool ret = false; + + mpext = skb ? mptcp_get_ext(skb) : NULL; + snd_data_fin_enable = READ_ONCE(msk->snd_data_fin_enable); + + if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) { + unsigned int map_size; + + map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64; + + remaining -= map_size; + dss_size = map_size; + if (mpext) + opts->ext_copy = *mpext; + + if (skb && snd_data_fin_enable) + mptcp_write_data_fin(subflow, skb, &opts->ext_copy); + ret = true; + } + + /* passive sockets msk will set the 'can_ack' after accept(), even + * if the first subflow may have the already the remote key handy + */ + opts->ext_copy.use_ack = 0; + if (!READ_ONCE(msk->can_ack)) { + *size = ALIGN(dss_size, 4); + return ret; + } + + if (READ_ONCE(msk->use_64bit_ack)) { + ack_size = TCPOLEN_MPTCP_DSS_ACK64; + opts->ext_copy.data_ack = READ_ONCE(msk->ack_seq); + opts->ext_copy.ack64 = 1; + } else { + ack_size = TCPOLEN_MPTCP_DSS_ACK32; + opts->ext_copy.data_ack32 = (uint32_t)READ_ONCE(msk->ack_seq); + opts->ext_copy.ack64 = 0; + } + opts->ext_copy.use_ack = 1; + + /* Add kind/length/subtype/flag overhead if mapping is not populated */ + if (dss_size == 0) + ack_size += TCPOLEN_MPTCP_DSS_BASE; + + dss_size += ack_size; + + *size = ALIGN(dss_size, 4); + return true; +} + +static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id, + struct in_addr *addr) +{ + u8 hmac[SHA256_DIGEST_SIZE]; + u8 msg[7]; + + msg[0] = addr_id; + memcpy(&msg[1], &addr->s_addr, 4); + msg[5] = 0; + msg[6] = 0; + + mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac); + + return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]); +} + +#if IS_ENABLED(CONFIG_MPTCP_IPV6) +static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id, + struct in6_addr *addr) +{ + u8 hmac[SHA256_DIGEST_SIZE]; + u8 msg[19]; + + msg[0] = addr_id; + memcpy(&msg[1], &addr->s6_addr, 16); + msg[17] = 0; + msg[18] = 0; + + mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac); + + return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]); +} +#endif + +static bool mptcp_established_options_add_addr(struct sock *sk, + unsigned int *size, + unsigned int remaining, + struct mptcp_out_options *opts) +{ + struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); + struct mptcp_sock *msk = mptcp_sk(subflow->conn); + struct mptcp_addr_info saddr; + bool echo; + int len; + + if (!mptcp_pm_should_add_signal(msk) || + !(mptcp_pm_add_addr_signal(msk, remaining, &saddr, &echo))) + return false; + + len = mptcp_add_addr_len(saddr.family, echo); + if (remaining < len) + return false; + + *size = len; + opts->addr_id = saddr.id; + if (saddr.family == AF_INET) { + opts->suboptions |= OPTION_MPTCP_ADD_ADDR; + opts->addr = saddr.addr; + if (!echo) { + opts->ahmac = add_addr_generate_hmac(msk->local_key, + msk->remote_key, + opts->addr_id, + &opts->addr); + } + } +#if IS_ENABLED(CONFIG_MPTCP_IPV6) + else if (saddr.family == AF_INET6) { + opts->suboptions |= OPTION_MPTCP_ADD_ADDR6; + opts->addr6 = saddr.addr6; + if (!echo) { + opts->ahmac = add_addr6_generate_hmac(msk->local_key, + msk->remote_key, + opts->addr_id, + &opts->addr6); + } + } +#endif + pr_debug("addr_id=%d, ahmac=%llu, echo=%d", opts->addr_id, opts->ahmac, echo); + + return true; +} + +static bool mptcp_established_options_rm_addr(struct sock *sk, + unsigned int *size, + unsigned int remaining, + struct mptcp_out_options *opts) +{ + struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); + struct mptcp_sock *msk = mptcp_sk(subflow->conn); + u8 rm_id; + + if (!mptcp_pm_should_rm_signal(msk) || + !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_id))) + return false; + + if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE) + return false; + + *size = TCPOLEN_MPTCP_RM_ADDR_BASE; + opts->suboptions |= OPTION_MPTCP_RM_ADDR; + opts->rm_id = rm_id; + + pr_debug("rm_id=%d", opts->rm_id); + + return true; +} + +bool mptcp_established_options(struct sock *sk, struct sk_buff *skb, + unsigned int *size, unsigned int remaining, + struct mptcp_out_options *opts) +{ + unsigned int opt_size = 0; + bool ret = false; + + opts->suboptions = 0; + + if (unlikely(mptcp_check_fallback(sk))) + return false; + + /* prevent adding of any MPTCP related options on reset packet + * until we support MP_TCPRST/MP_FASTCLOSE + */ + if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) + return false; + + if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts)) + ret = true; + else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining, + opts)) + ret = true; + + /* we reserved enough space for the above options, and exceeding the + * TCP option space would be fatal + */ + if (WARN_ON_ONCE(opt_size > remaining)) + return false; + + *size += opt_size; + remaining -= opt_size; + if (mptcp_established_options_add_addr(sk, &opt_size, remaining, opts)) { + *size += opt_size; + remaining -= opt_size; + ret = true; + } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) { + *size += opt_size; + remaining -= opt_size; + ret = true; + } + + return ret; +} + +bool mptcp_synack_options(const struct request_sock *req, unsigned int *size, + struct mptcp_out_options *opts) +{ + struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req); + + if (subflow_req->mp_capable) { + opts->suboptions = OPTION_MPTCP_MPC_SYNACK; + opts->sndr_key = subflow_req->local_key; + *size = TCPOLEN_MPTCP_MPC_SYNACK; + pr_debug("subflow_req=%p, local_key=%llu", + subflow_req, subflow_req->local_key); + return true; + } else if (subflow_req->mp_join) { + opts->suboptions = OPTION_MPTCP_MPJ_SYNACK; + opts->backup = subflow_req->backup; + opts->join_id = subflow_req->local_id; + opts->thmac = subflow_req->thmac; + opts->nonce = subflow_req->local_nonce; + pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u", + subflow_req, opts->backup, opts->join_id, + opts->thmac, opts->nonce); + *size = TCPOLEN_MPTCP_MPJ_SYNACK; + return true; + } + return false; +} + +static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk, + struct mptcp_subflow_context *subflow, + struct sk_buff *skb, + struct mptcp_options_received *mp_opt) +{ + /* here we can process OoO, in-window pkts, only in-sequence 4th ack + * will make the subflow fully established + */ + if (likely(subflow->fully_established)) { + /* on passive sockets, check for 3rd ack retransmission + * note that msk is always set by subflow_syn_recv_sock() + * for mp_join subflows + */ + if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 && + TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq && + subflow->mp_join && mp_opt->mp_join && + READ_ONCE(msk->pm.server_side)) + tcp_send_ack(ssk); + goto fully_established; + } + + /* we must process OoO packets before the first subflow is fully + * established. OoO packets are instead a protocol violation + * for MP_JOIN subflows as the peer must not send any data + * before receiving the forth ack - cfr. RFC 8684 section 3.2. + */ + if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) { + if (subflow->mp_join) + goto reset; + return subflow->mp_capable; + } + + if (mp_opt->dss && mp_opt->use_ack) { + /* subflows are fully established as soon as we get any + * additional ack. + */ + subflow->fully_established = 1; + WRITE_ONCE(msk->fully_established, true); + goto fully_established; + } + + /* If the first established packet does not contain MP_CAPABLE + data + * then fallback to TCP. Fallback scenarios requires a reset for + * MP_JOIN subflows. + */ + if (!mp_opt->mp_capable) { + if (subflow->mp_join) + goto reset; + subflow->mp_capable = 0; + pr_fallback(msk); + __mptcp_do_fallback(msk); + return false; + } + + if (unlikely(!READ_ONCE(msk->pm.server_side))) + pr_warn_once("bogus mpc option on established client sk"); + mptcp_subflow_fully_established(subflow, mp_opt); + +fully_established: + if (likely(subflow->pm_notified)) + return true; + + subflow->pm_notified = 1; + if (subflow->mp_join) { + clear_3rdack_retransmission(ssk); + mptcp_pm_subflow_established(msk, subflow); + } else { + mptcp_pm_fully_established(msk); + } + return true; + +reset: + mptcp_subflow_reset(ssk); + return false; +} + +static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit) +{ + u32 old_ack32, cur_ack32; + + if (use_64bit) + return cur_ack; + + old_ack32 = (u32)old_ack; + cur_ack32 = (u32)cur_ack; + cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32; + if (unlikely(before(cur_ack32, old_ack32))) + return cur_ack + (1LL << 32); + return cur_ack; +} + +static void update_una(struct mptcp_sock *msk, + struct mptcp_options_received *mp_opt) +{ + u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una); + u64 write_seq = READ_ONCE(msk->write_seq); + + /* avoid ack expansion on update conflict, to reduce the risk of + * wrongly expanding to a future ack sequence number, which is way + * more dangerous than missing an ack + */ + new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64); + + /* ACK for data not even sent yet? Ignore. */ + if (after64(new_snd_una, write_seq)) + new_snd_una = old_snd_una; + + while (after64(new_snd_una, old_snd_una)) { + snd_una = old_snd_una; + old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una, + new_snd_una); + if (old_snd_una == snd_una) { + mptcp_data_acked((struct sock *)msk); + break; + } + } +} + +bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit) +{ + /* Skip if DATA_FIN was already received. + * If updating simultaneously with the recvmsg loop, values + * should match. If they mismatch, the peer is misbehaving and + * we will prefer the most recent information. + */ + if (READ_ONCE(msk->rcv_data_fin) || !READ_ONCE(msk->first)) + return false; + + WRITE_ONCE(msk->rcv_data_fin_seq, + expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit)); + WRITE_ONCE(msk->rcv_data_fin, 1); + + return true; +} + +static bool add_addr_hmac_valid(struct mptcp_sock *msk, + struct mptcp_options_received *mp_opt) +{ + u64 hmac = 0; + + if (mp_opt->echo) + return true; + + if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) + hmac = add_addr_generate_hmac(msk->remote_key, + msk->local_key, + mp_opt->addr_id, &mp_opt->addr); +#if IS_ENABLED(CONFIG_MPTCP_IPV6) + else + hmac = add_addr6_generate_hmac(msk->remote_key, + msk->local_key, + mp_opt->addr_id, &mp_opt->addr6); +#endif + + pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n", + msk, (unsigned long long)hmac, + (unsigned long long)mp_opt->ahmac); + + return hmac == mp_opt->ahmac; +} + +void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) +{ + struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); + struct mptcp_sock *msk = mptcp_sk(subflow->conn); + struct mptcp_options_received mp_opt; + struct mptcp_ext *mpext; + + if (__mptcp_check_fallback(msk)) + return; + + mptcp_get_options(skb, &mp_opt); + if (!check_fully_established(msk, sk, subflow, skb, &mp_opt)) + return; + + if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) { + struct mptcp_addr_info addr; + + addr.port = htons(mp_opt.port); + addr.id = mp_opt.addr_id; + if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) { + addr.family = AF_INET; + addr.addr = mp_opt.addr; + } +#if IS_ENABLED(CONFIG_MPTCP_IPV6) + else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) { + addr.family = AF_INET6; + addr.addr6 = mp_opt.addr6; + } +#endif + if (!mp_opt.echo) { + mptcp_pm_add_addr_received(msk, &addr); + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR); + } else { + mptcp_pm_del_add_timer(msk, &addr); + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD); + } + mp_opt.add_addr = 0; + } + + if (mp_opt.rm_addr) { + mptcp_pm_rm_addr_received(msk, mp_opt.rm_id); + mp_opt.rm_addr = 0; + } + + if (!mp_opt.dss) + return; + + /* we can't wait for recvmsg() to update the ack_seq, otherwise + * monodirectional flows will stuck + */ + if (mp_opt.use_ack) + update_una(msk, &mp_opt); + + /* Zero-data-length packets are dropped by the caller and not + * propagated to the MPTCP layer, so the skb extension does not + * need to be allocated or populated. DATA_FIN information, if + * present, needs to be updated here before the skb is freed. + */ + if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) { + if (mp_opt.data_fin && mp_opt.data_len == 1 && + mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) && + schedule_work(&msk->work)) + sock_hold(subflow->conn); + + return; + } + + mpext = skb_ext_add(skb, SKB_EXT_MPTCP); + if (!mpext) + return; + + memset(mpext, 0, sizeof(*mpext)); + + if (mp_opt.use_map) { + if (mp_opt.mpc_map) { + /* this is an MP_CAPABLE carrying MPTCP data + * we know this map the first chunk of data + */ + mptcp_crypto_key_sha(subflow->remote_key, NULL, + &mpext->data_seq); + mpext->data_seq++; + mpext->subflow_seq = 1; + mpext->dsn64 = 1; + mpext->mpc_map = 1; + mpext->data_fin = 0; + } else { + mpext->data_seq = mp_opt.data_seq; + mpext->subflow_seq = mp_opt.subflow_seq; + mpext->dsn64 = mp_opt.dsn64; + mpext->data_fin = mp_opt.data_fin; + } + mpext->data_len = mp_opt.data_len; + mpext->use_map = 1; + } +} + +void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts) +{ + if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK | + OPTION_MPTCP_MPC_ACK) & opts->suboptions) { + u8 len; + + if (OPTION_MPTCP_MPC_SYN & opts->suboptions) + len = TCPOLEN_MPTCP_MPC_SYN; + else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) + len = TCPOLEN_MPTCP_MPC_SYNACK; + else if (opts->ext_copy.data_len) + len = TCPOLEN_MPTCP_MPC_ACK_DATA; + else + len = TCPOLEN_MPTCP_MPC_ACK; + + *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len, + MPTCP_SUPPORTED_VERSION, + MPTCP_CAP_HMAC_SHA256); + + if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) & + opts->suboptions)) + goto mp_capable_done; + + put_unaligned_be64(opts->sndr_key, ptr); + ptr += 2; + if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions)) + goto mp_capable_done; + + put_unaligned_be64(opts->rcvr_key, ptr); + ptr += 2; + if (!opts->ext_copy.data_len) + goto mp_capable_done; + + put_unaligned_be32(opts->ext_copy.data_len << 16 | + TCPOPT_NOP << 8 | TCPOPT_NOP, ptr); + ptr += 1; + } + +mp_capable_done: + if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) { + if (opts->ahmac) + *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, + TCPOLEN_MPTCP_ADD_ADDR, 0, + opts->addr_id); + else + *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, + TCPOLEN_MPTCP_ADD_ADDR_BASE, + MPTCP_ADDR_ECHO, + opts->addr_id); + memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4); + ptr += 1; + if (opts->ahmac) { + put_unaligned_be64(opts->ahmac, ptr); + ptr += 2; + } + } + +#if IS_ENABLED(CONFIG_MPTCP_IPV6) + if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) { + if (opts->ahmac) + *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, + TCPOLEN_MPTCP_ADD_ADDR6, 0, + opts->addr_id); + else + *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, + TCPOLEN_MPTCP_ADD_ADDR6_BASE, + MPTCP_ADDR_ECHO, + opts->addr_id); + memcpy((u8 *)ptr, opts->addr6.s6_addr, 16); + ptr += 4; + if (opts->ahmac) { + put_unaligned_be64(opts->ahmac, ptr); + ptr += 2; + } + } +#endif + + if (OPTION_MPTCP_RM_ADDR & opts->suboptions) { + *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR, + TCPOLEN_MPTCP_RM_ADDR_BASE, + 0, opts->rm_id); + } + + if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) { + *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, + TCPOLEN_MPTCP_MPJ_SYN, + opts->backup, opts->join_id); + put_unaligned_be32(opts->token, ptr); + ptr += 1; + put_unaligned_be32(opts->nonce, ptr); + ptr += 1; + } + + if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) { + *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, + TCPOLEN_MPTCP_MPJ_SYNACK, + opts->backup, opts->join_id); + put_unaligned_be64(opts->thmac, ptr); + ptr += 2; + put_unaligned_be32(opts->nonce, ptr); + ptr += 1; + } + + if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) { + *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, + TCPOLEN_MPTCP_MPJ_ACK, 0, 0); + memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN); + ptr += 5; + } + + if (opts->ext_copy.use_ack || opts->ext_copy.use_map) { + struct mptcp_ext *mpext = &opts->ext_copy; + u8 len = TCPOLEN_MPTCP_DSS_BASE; + u8 flags = 0; + + if (mpext->use_ack) { + flags = MPTCP_DSS_HAS_ACK; + if (mpext->ack64) { + len += TCPOLEN_MPTCP_DSS_ACK64; + flags |= MPTCP_DSS_ACK64; + } else { + len += TCPOLEN_MPTCP_DSS_ACK32; + } + } + + if (mpext->use_map) { + len += TCPOLEN_MPTCP_DSS_MAP64; + + /* Use only 64-bit mapping flags for now, add + * support for optional 32-bit mappings later. + */ + flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64; + if (mpext->data_fin) + flags |= MPTCP_DSS_DATA_FIN; + } + + *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags); + + if (mpext->use_ack) { + if (mpext->ack64) { + put_unaligned_be64(mpext->data_ack, ptr); + ptr += 2; + } else { + put_unaligned_be32(mpext->data_ack32, ptr); + ptr += 1; + } + } + + if (mpext->use_map) { + put_unaligned_be64(mpext->data_seq, ptr); + ptr += 2; + put_unaligned_be32(mpext->subflow_seq, ptr); + ptr += 1; + put_unaligned_be32(mpext->data_len << 16 | + TCPOPT_NOP << 8 | TCPOPT_NOP, ptr); + } + } +} |