From dc87efdb1a5cd46134a9d490480160e303bc6eef Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 1 Apr 2021 16:19:44 -0700 Subject: 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. Signed-off-by: Florian Westphal Signed-off-by: Mat Martineau Signed-off-by: David S. Miller --- net/mptcp/options.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 62 insertions(+), 5 deletions(-) (limited to 'net/mptcp/options.c') diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 68361d28dc67..4b7119eb2c31 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 @@ mp_capable_done: 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 @@ mp_capable_done: 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); -- cgit v1.2.3-58-ga151