From 7954ce55c00048d5e761ee40ccbc6554990e83ea Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 1 Apr 2021 05:36:48 +0000 Subject: [PATCH] mptcp: add mptcp reset option support The MPTCP reset option allows to carry a mptcp-specific error code that provides more information on the nature of a connection reset. Reset option data received gets stored in the subflow context so it can be sent to userspace via the 'subflow closed' netlink event. When a subflow is closed, the desired error code that should be sent to the peer is also placed in the subflow context structure. If a reset is sent before subflow establishment could complete, e.g. on HMAC failure during an MP_JOIN operation, the mptcp skb extension is used to store the reset information. Reviewed-by: Mat Martineau Signed-off-by: Florian Westphal --- include/net/mptcp.h | 18 ++++++++-- include/uapi/linux/mptcp.h | 11 +++++++ net/ipv4/tcp_ipv4.c | 21 ++++++++++-- net/ipv6/tcp_ipv6.c | 14 +++++++- net/mptcp/options.c | 67 +++++++++++++++++++++++++++++++++++--- net/mptcp/pm_netlink.c | 12 +++++++ net/mptcp/protocol.c | 12 +++++-- net/mptcp/protocol.h | 14 +++++++- net/mptcp/subflow.c | 30 ++++++++++++++--- 9 files changed, 180 insertions(+), 19 deletions(-) diff --git a/include/net/mptcp.h b/include/net/mptcp.h index cea69c8015959..16fe34d139c3c 100644 --- a/include/net/mptcp.h +++ b/include/net/mptcp.h @@ -30,8 +30,8 @@ struct mptcp_ext { ack64:1, mpc_map:1, frozen:1, - __unused:1; - /* one byte hole */ + reset_transient:1; + u8 reset_reason:4; }; #define MPTCP_RM_IDS_MAX 8 @@ -58,6 +58,8 @@ struct mptcp_out_options { struct mptcp_rm_list rm_list; u8 join_id; u8 backup; + u8 reset_reason:4; + u8 reset_transient:1; u32 nonce; u64 thmac; u32 token; @@ -156,6 +158,16 @@ void mptcp_seq_show(struct seq_file *seq); int mptcp_subflow_init_cookie_req(struct request_sock *req, const struct sock *sk_listener, struct sk_buff *skb); + +__be32 mptcp_get_reset_option(const struct sk_buff *skb); + +static inline __be32 mptcp_reset_option(const struct sk_buff *skb) +{ + if (skb_ext_exist(skb, SKB_EXT_MPTCP)) + return mptcp_get_reset_option(skb); + + return htonl(0u); +} #else static inline void mptcp_init(void) @@ -236,6 +248,8 @@ static inline int mptcp_subflow_init_cookie_req(struct request_sock *req, { return 0; /* TCP fallback */ } + +static inline __be32 mptcp_reset_option(const struct sk_buff *skb) { return htonl(0u); } #endif /* CONFIG_MPTCP */ #if IS_ENABLED(CONFIG_MPTCP_IPV6) diff --git a/include/uapi/linux/mptcp.h b/include/uapi/linux/mptcp.h index e1172c1ffdfde..8eb3c0844bfff 100644 --- a/include/uapi/linux/mptcp.h +++ b/include/uapi/linux/mptcp.h @@ -174,10 +174,21 @@ enum mptcp_event_attr { MPTCP_ATTR_FLAGS, /* u16 */ MPTCP_ATTR_TIMEOUT, /* u32 */ MPTCP_ATTR_IF_IDX, /* s32 */ + MPTCP_ATTR_RESET_REASON,/* u32 */ + MPTCP_ATTR_RESET_FLAGS, /* u32 */ __MPTCP_ATTR_AFTER_LAST }; #define MPTCP_ATTR_MAX (__MPTCP_ATTR_AFTER_LAST - 1) +/* MPTCP Reset reason codes, rfc8684 */ +#define MPTCP_RST_EUNSPEC 0 +#define MPTCP_RST_EMPTCP 1 +#define MPTCP_RST_ERESOURCE 2 +#define MPTCP_RST_EPROHIBIT 3 +#define MPTCP_RST_EWQ2BIG 4 +#define MPTCP_RST_EBADPERF 5 +#define MPTCP_RST_EMIDDLEBOX 6 + #endif /* _UAPI_MPTCP_H */ diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index daad4f99db328..e092c5a9dd1c0 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -655,14 +655,18 @@ EXPORT_SYMBOL(tcp_v4_send_check); * Exception: precedence violation. We do not implement it in any case. */ +#ifdef CONFIG_TCP_MD5SIG +#define OPTION_BYTES TCPOLEN_MD5SIG_ALIGNED +#else +#define OPTION_BYTES sizeof(__be32) +#endif + static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb) { const struct tcphdr *th = tcp_hdr(skb); struct { struct tcphdr th; -#ifdef CONFIG_TCP_MD5SIG - __be32 opt[(TCPOLEN_MD5SIG_ALIGNED >> 2)]; -#endif + __be32 opt[OPTION_BYTES / sizeof(__be32)]; } rep; struct ip_reply_arg arg; #ifdef CONFIG_TCP_MD5SIG @@ -770,6 +774,17 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb) ip_hdr(skb)->daddr, &rep.th); } #endif + /* Can't co-exist with TCPMD5, hence check rep.opt[0] */ + if (rep.opt[0] == 0) { + __be32 mrst = mptcp_reset_option(skb); + + if (mrst) { + rep.opt[0] = mrst; + arg.iov[0].iov_len += sizeof(mrst); + rep.th.doff = arg.iov[0].iov_len / 4; + } + } + arg.csum = csum_tcpudp_nofold(ip_hdr(skb)->daddr, ip_hdr(skb)->saddr, /* XXX */ arg.iov[0].iov_len, IPPROTO_TCP, 0); diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index d0f007741e8ed..e9cedb918b7fc 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -879,8 +879,8 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32 struct net *net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev); struct sock *ctl_sk = net->ipv6.tcp_sk; unsigned int tot_len = sizeof(struct tcphdr); + __be32 mrst = 0, *topt; struct dst_entry *dst; - __be32 *topt; __u32 mark = 0; if (tsecr) @@ -890,6 +890,15 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32 tot_len += TCPOLEN_MD5SIG_ALIGNED; #endif +#ifdef CONFIG_MPTCP + if (rst && !key) { + mrst = mptcp_reset_option(skb); + + if (mrst) + tot_len += sizeof(__be32); + } +#endif + buff = alloc_skb(MAX_HEADER + sizeof(struct ipv6hdr) + tot_len, GFP_ATOMIC); if (!buff) @@ -920,6 +929,9 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32 *topt++ = htonl(tsecr); } + if (mrst) + *topt++ = mrst; + #ifdef CONFIG_TCP_MD5SIG if (key) { *topt++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 68361d28dc676..4b7119eb2c31c 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -305,6 +305,18 @@ static void mptcp_parse_option(const struct sk_buff *skb, mp_opt->fastclose = 1; break; + case MPTCPOPT_RST: + if (opsize != TCPOLEN_MPTCP_RST) + break; + + if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) + break; + mp_opt->reset = 1; + flags = *ptr++; + mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT; + mp_opt->reset_reason = *ptr; + break; + default: break; } @@ -327,6 +339,7 @@ void mptcp_get_options(const struct sk_buff *skb, mp_opt->rm_addr = 0; mp_opt->dss = 0; mp_opt->mp_prio = 0; + mp_opt->reset = 0; length = (th->doff * 4) - sizeof(struct tcphdr); ptr = (const unsigned char *)(th + 1); @@ -726,6 +739,22 @@ static bool mptcp_established_options_mp_prio(struct sock *sk, return true; } +static noinline void mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb, + unsigned int *size, + unsigned int remaining, + struct mptcp_out_options *opts) +{ + const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); + + if (remaining < TCPOLEN_MPTCP_RST) + return; + + *size = TCPOLEN_MPTCP_RST; + opts->suboptions |= OPTION_MPTCP_RST; + opts->reset_transient = subflow->reset_transient; + opts->reset_reason = subflow->reset_reason; +} + bool mptcp_established_options(struct sock *sk, struct sk_buff *skb, unsigned int *size, unsigned int remaining, struct mptcp_out_options *opts) @@ -741,11 +770,10 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb, if (unlikely(__mptcp_check_fallback(msk))) 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 (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) { + mptcp_established_options_rst(sk, skb, size, remaining, opts); + return true; + } snd_data_fin = mptcp_data_fin_enabled(msk); if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts)) @@ -1062,6 +1090,12 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) mp_opt.mp_prio = 0; } + if (mp_opt.reset) { + subflow->reset_seen = 1; + subflow->reset_reason = mp_opt.reset_reason; + subflow->reset_transient = mp_opt.reset_transient; + } + if (!mp_opt.dss) return; @@ -1289,6 +1323,12 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp, ptr += 5; } + if (OPTION_MPTCP_RST & opts->suboptions) + *ptr++ = mptcp_option(MPTCPOPT_RST, + TCPOLEN_MPTCP_RST, + opts->reset_transient, + opts->reset_reason); + if (opts->ext_copy.use_ack || opts->ext_copy.use_map) { struct mptcp_ext *mpext = &opts->ext_copy; u8 len = TCPOLEN_MPTCP_DSS_BASE; @@ -1340,3 +1380,20 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp, if (tp) mptcp_set_rwin(tp); } + +__be32 mptcp_get_reset_option(const struct sk_buff *skb) +{ + const struct mptcp_ext *ext = mptcp_get_ext(skb); + u8 flags, reason; + + if (ext) { + flags = ext->reset_transient; + reason = ext->reset_reason; + + return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST, + flags, reason); + } + + return htonl(0u); +} +EXPORT_SYMBOL_GPL(mptcp_get_reset_option); diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index cadafafa1049f..51be6c34b339f 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -1687,9 +1687,21 @@ static int mptcp_event_sub_closed(struct sk_buff *skb, const struct mptcp_sock *msk, const struct sock *ssk) { + const struct mptcp_subflow_context *sf; + if (mptcp_event_put_token_and_ssk(skb, msk, ssk)) return -EMSGSIZE; + sf = mptcp_subflow_ctx(ssk); + if (!sf->reset_seen) + return 0; + + if (nla_put_u32(skb, MPTCP_ATTR_RESET_REASON, sf->reset_reason)) + return -EMSGSIZE; + + if (nla_put_u32(skb, MPTCP_ATTR_RESET_FLAGS, sf->reset_transient)) + return -EMSGSIZE; + return 0; } diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index fb24958d51067..e0b381ae99af5 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2968,14 +2968,18 @@ bool mptcp_finish_join(struct sock *ssk) pr_debug("msk=%p, subflow=%p", msk, subflow); /* mptcp socket already closing? */ - if (!mptcp_is_fully_established(parent)) + if (!mptcp_is_fully_established(parent)) { + subflow->reset_reason = MPTCP_RST_EMPTCP; return false; + } if (!msk->pm.server_side) goto out; - if (!mptcp_pm_allow_new_subflow(msk)) + if (!mptcp_pm_allow_new_subflow(msk)) { + subflow->reset_reason = MPTCP_RST_EPROHIBIT; return false; + } /* active connections are already on conn_list, and we can't acquire * msk lock here. @@ -2989,8 +2993,10 @@ bool mptcp_finish_join(struct sock *ssk) sock_hold(ssk); } spin_unlock_bh(&msk->join_list_lock); - if (!ret) + if (!ret) { + subflow->reset_reason = MPTCP_RST_EPROHIBIT; return false; + } /* attach to msk socket only after we are sure he will deal with us * at close time diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 9975993a8fcd7..e53a9568d5877 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -26,6 +26,7 @@ #define OPTION_MPTCP_RM_ADDR BIT(8) #define OPTION_MPTCP_FASTCLOSE BIT(9) #define OPTION_MPTCP_PRIO BIT(10) +#define OPTION_MPTCP_RST BIT(11) /* MPTCP option subtypes */ #define MPTCPOPT_MP_CAPABLE 0 @@ -36,6 +37,7 @@ #define MPTCPOPT_MP_PRIO 5 #define MPTCPOPT_MP_FAIL 6 #define MPTCPOPT_MP_FASTCLOSE 7 +#define MPTCPOPT_RST 8 /* MPTCP suboption lengths */ #define TCPOLEN_MPTCP_MPC_SYN 4 @@ -65,6 +67,7 @@ #define TCPOLEN_MPTCP_PRIO 3 #define TCPOLEN_MPTCP_PRIO_ALIGN 4 #define TCPOLEN_MPTCP_FASTCLOSE 12 +#define TCPOLEN_MPTCP_RST 4 /* MPTCP MP_JOIN flags */ #define MPTCPOPT_BACKUP BIT(0) @@ -94,6 +97,9 @@ /* MPTCP MP_PRIO flags */ #define MPTCP_PRIO_BKUP BIT(0) +/* MPTCP TCPRST flags */ +#define MPTCP_RST_TRANSIENT BIT(0) + /* MPTCP socket flags */ #define MPTCP_DATA_READY 0 #define MPTCP_NOSPACE 1 @@ -123,6 +129,7 @@ struct mptcp_options_received { u16 mp_capable : 1, mp_join : 1, fastclose : 1, + reset : 1, dss : 1, add_addr : 1, rm_addr : 1, @@ -152,6 +159,8 @@ struct mptcp_options_received { }; u64 ahmac; u16 port; + u8 reset_reason:4; + u8 reset_transient:1; }; static inline __be32 mptcp_option(u8 subopt, u8 len, u8 nib, u8 field) @@ -422,6 +431,9 @@ struct mptcp_subflow_context { u8 hmac[MPTCPOPT_HMAC_LEN]; u8 local_id; u8 remote_id; + u8 reset_seen:1; + u8 reset_transient:1; + u8 reset_reason:4; long delegated_status; struct list_head delegated_node; /* link into delegated_action, protected by local BH */ @@ -747,7 +759,7 @@ unsigned int mptcp_pm_get_add_addr_accept_max(struct mptcp_sock *msk); unsigned int mptcp_pm_get_subflows_max(struct mptcp_sock *msk); unsigned int mptcp_pm_get_local_addr_max(struct mptcp_sock *msk); -static inline struct mptcp_ext *mptcp_get_ext(struct sk_buff *skb) +static inline struct mptcp_ext *mptcp_get_ext(const struct sk_buff *skb) { return (struct mptcp_ext *)skb_ext_find(skb, SKB_EXT_MPTCP); } diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 7a5f50d00d4b7..223d6be5fc3bb 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -115,6 +115,16 @@ static bool subflow_use_different_sport(struct mptcp_sock *msk, const struct soc return inet_sk(sk)->inet_sport != inet_sk((struct sock *)msk)->inet_sport; } +static void subflow_add_reset_reason(struct sk_buff *skb, u8 reason) +{ + struct mptcp_ext *mpext = skb_ext_add(skb, SKB_EXT_MPTCP); + + if (mpext) { + memset(mpext, 0, sizeof(*mpext)); + mpext->reset_reason = reason; + } +} + /* Init mptcp request socket. * * Returns an error code if a JOIN has failed and a TCP reset @@ -190,8 +200,10 @@ static int subflow_check_req(struct request_sock *req, subflow_req->msk = subflow_token_join_request(req); /* Can't fall back to TCP in this case. */ - if (!subflow_req->msk) + if (!subflow_req->msk) { + subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP); return -EPERM; + } if (subflow_use_different_sport(subflow_req->msk, sk_listener)) { pr_debug("syn inet_sport=%d %d", @@ -400,8 +412,10 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb) } else if (subflow->request_join) { u8 hmac[SHA256_DIGEST_SIZE]; - if (!mp_opt.mp_join) + if (!mp_opt.mp_join) { + subflow->reset_reason = MPTCP_RST_EMPTCP; goto do_reset; + } subflow->thmac = mp_opt.thmac; subflow->remote_nonce = mp_opt.nonce; @@ -410,6 +424,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb) if (!subflow_thmac_valid(subflow)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC); + subflow->reset_reason = MPTCP_RST_EMPTCP; goto do_reset; } @@ -438,6 +453,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb) return; do_reset: + subflow->reset_transient = 0; mptcp_subflow_reset(sk); } @@ -654,8 +670,10 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk, * to reset the context to non MPTCP status. */ if (!ctx || fallback) { - if (fallback_is_fatal) + if (fallback_is_fatal) { + subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP); goto dispose_child; + } subflow_drop_ctx(child); goto out; @@ -690,8 +708,10 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk, struct mptcp_sock *owner; owner = subflow_req->msk; - if (!owner) + if (!owner) { + subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT); goto dispose_child; + } /* move the msk reference ownership to the subflow */ subflow_req->msk = NULL; @@ -1056,6 +1076,8 @@ static bool subflow_check_data_avail(struct sock *ssk) smp_wmb(); ssk->sk_error_report(ssk); tcp_set_state(ssk, TCP_CLOSE); + subflow->reset_transient = 0; + subflow->reset_reason = MPTCP_RST_EMPTCP; tcp_send_active_reset(ssk, GFP_ATOMIC); subflow->data_avail = 0; return false;