From: Paolo Abeni pabeni@redhat.com
[ Upstream commit d582484726c4c46c8580923e855665fb91e3463e ]
Additional/MP_JOIN subflows that do not pass some initial handshake tests currently causes fallback to TCP. That is an RFC violation: we should instead reset the subflow and leave the the msk untouched.
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/91 Fixes: f296234c98a8 ("mptcp: Add handling of incoming MP_JOIN requests") Reviewed-by: Mat Martineau mathew.j.martineau@linux.intel.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/options.c | 32 +++++++++++++++++++++++++------- net/mptcp/protocol.h | 1 + net/mptcp/subflow.c | 10 ++++++++-- 3 files changed, 34 insertions(+), 9 deletions(-)
--- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -626,6 +626,12 @@ bool mptcp_established_options(struct so 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, @@ -676,7 +682,7 @@ bool mptcp_synack_options(const struct r return false; }
-static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk, +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) @@ -693,15 +699,20 @@ static bool check_fully_established(stru 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(sk); + tcp_send_ack(ssk); goto fully_established; }
- /* we should process OoO packets before the first subflow is fully - * established, but not expected for MP_JOIN subflows + /* 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 (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 @@ -713,9 +724,12 @@ static bool check_fully_established(stru }
/* If the first established packet does not contain MP_CAPABLE + data - * then fallback to TCP + * 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); @@ -732,12 +746,16 @@ fully_established:
subflow->pm_notified = 1; if (subflow->mp_join) { - clear_3rdack_retransmission(sk); + 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) --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -348,6 +348,7 @@ void mptcp_subflow_fully_established(str struct mptcp_options_received *mp_opt); bool mptcp_subflow_data_available(struct sock *sk); void __init mptcp_subflow_init(void); +void mptcp_subflow_reset(struct sock *ssk);
/* called with sk socket lock held */ int __mptcp_subflow_connect(struct sock *sk, int ifindex, --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -270,6 +270,13 @@ static bool subflow_thmac_valid(struct m return thmac == subflow->thmac; }
+void mptcp_subflow_reset(struct sock *ssk) +{ + tcp_set_state(ssk, TCP_CLOSE); + tcp_send_active_reset(ssk, GFP_ATOMIC); + tcp_done(ssk); +} + static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); @@ -342,8 +349,7 @@ fallback: return;
do_reset: - tcp_send_active_reset(sk, GFP_ATOMIC); - tcp_done(sk); + mptcp_subflow_reset(sk); }
struct request_sock_ops mptcp_subflow_request_sock_ops;