// SPDX-License-Identifier: GPL-2.0 /* Multipath TCP * * Copyright (c) 2017 - 2019, Intel Corporation. */ #define pr_fmt(fmt) "MPTCP: " fmt #include #include #include #include #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->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 { pr_warn("MP_JOIN bad option size"); 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%s: id=%d, echo=%d", (mp_opt->family == MPTCP_ADDR_IPVERSION_6) ? "6" : "", 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: 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 = tp->srtt_us << 1; else timeout = TCP_TIMEOUT_INIT; 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 = mptcp_data_fin_enabled(msk); 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; WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk)); /* 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, 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); bool drop_other_suboptions = false; unsigned int opt_size = *size; struct mptcp_addr_info saddr; bool echo; int len; if (mptcp_pm_should_add_signal_ipv6(msk) && skb && skb_is_tcp_pure_ack(skb)) { pr_debug("drop other suboptions"); opts->suboptions = 0; remaining += opt_size; drop_other_suboptions = true; } 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; if (drop_other_suboptions) *size -= opt_size; 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, skb, &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 (mp_opt->add_addr) { WRITE_ONCE(msk->fully_established, true); return true; } /* 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 ack_update_msk(struct mptcp_sock *msk, const struct sock *ssk, struct mptcp_options_received *mp_opt) { u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt); struct sock *sk = (struct sock *)msk; u64 old_snd_una; mptcp_data_lock(sk); /* 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 */ old_snd_una = msk->snd_una; 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, snd_nxt)) new_snd_una = old_snd_una; new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd; if (after64(new_wnd_end, msk->wnd_end)) { msk->wnd_end = new_wnd_end; if (mptcp_send_head(sk)) mptcp_schedule_work(sk); } if (after64(new_snd_una, old_snd_una)) { msk->snd_una = new_snd_una; __mptcp_data_acked(sk); } mptcp_data_unlock(sk); } 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) ack_update_msk(msk, sk, &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; } } static void mptcp_set_rwin(const struct tcp_sock *tp) { const struct sock *ssk = (const struct sock *)tp; const struct mptcp_subflow_context *subflow; struct mptcp_sock *msk; u64 ack_seq; subflow = mptcp_subflow_ctx(ssk); msk = mptcp_sk(subflow->conn); ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd; if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent))) WRITE_ONCE(msk->rcv_wnd_sent, ack_seq); } void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp, 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); } } if (tp) mptcp_set_rwin(tp); }