From f3589be0c420a3137e5902d15705ced6a36f3f43 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Wed, 4 May 2022 14:54:07 -0700 Subject: mptcp: never shrink offered window As per RFC, the offered MPTCP-level window should never shrink. While we currently track the right edge, we don't enforce the above constraint on the wire. Additionally, concurrent xmit on different subflows can end-up in erroneous right edge update. Address the above explicitly updating the announced window and protecting the update with an additional atomic operation (sic) Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: Jakub Kicinski --- net/mptcp/options.c | 52 +++++++++++++++++++++++++++++++++++++++++++++------- net/mptcp/protocol.c | 8 ++++---- net/mptcp/protocol.h | 2 +- 3 files changed, 50 insertions(+), 12 deletions(-) (limited to 'net/mptcp') diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 2570911735ab..3e3156cfe813 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -1224,20 +1224,58 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) return true; } -static void mptcp_set_rwin(const struct tcp_sock *tp) +static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th) { const struct sock *ssk = (const struct sock *)tp; - const struct mptcp_subflow_context *subflow; + struct mptcp_subflow_context *subflow; + u64 ack_seq, rcv_wnd_old, rcv_wnd_new; struct mptcp_sock *msk; - u64 ack_seq; + u32 new_win; + u64 win; subflow = mptcp_subflow_ctx(ssk); msk = mptcp_sk(subflow->conn); - ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd; + ack_seq = READ_ONCE(msk->ack_seq); + rcv_wnd_new = ack_seq + tp->rcv_wnd; + + rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent); + if (after64(rcv_wnd_new, rcv_wnd_old)) { + u64 rcv_wnd; - if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent))) - WRITE_ONCE(msk->rcv_wnd_sent, ack_seq); + for (;;) { + rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new); + + if (rcv_wnd == rcv_wnd_old) + break; + if (before64(rcv_wnd_new, rcv_wnd)) + goto raise_win; + rcv_wnd_old = rcv_wnd; + } + return; + } + + if (rcv_wnd_new != rcv_wnd_old) { +raise_win: + win = rcv_wnd_old - ack_seq; + tp->rcv_wnd = min_t(u64, win, U32_MAX); + new_win = tp->rcv_wnd; + + /* Make sure we do not exceed the maximum possible + * scaled window. + */ + if (unlikely(th->syn)) + new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale; + if (!tp->rx_opt.rcv_wscale && + sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows) + new_win = min(new_win, MAX_TCP_WINDOW); + else + new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); + + /* RFC1323 scaling applied */ + new_win >>= tp->rx_opt.rcv_wscale; + th->window = htons(new_win); + } } u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum) @@ -1554,7 +1592,7 @@ mp_capable_done: } if (tp) - mptcp_set_rwin(tp); + mptcp_set_rwin(tp, th); } __be32 mptcp_get_reset_option(const struct sk_buff *skb) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 961c2aba2a11..9e46cc89a8f7 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -216,7 +216,7 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) seq = MPTCP_SKB_CB(skb)->map_seq; end_seq = MPTCP_SKB_CB(skb)->end_seq; - max_seq = READ_ONCE(msk->rcv_wnd_sent); + max_seq = atomic64_read(&msk->rcv_wnd_sent); pr_debug("msk=%p seq=%llx limit=%llx empty=%d", msk, seq, max_seq, RB_EMPTY_ROOT(&msk->out_of_order_queue)); @@ -225,7 +225,7 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) mptcp_drop(sk, skb); pr_debug("oow by %lld, rcv_wnd_sent %llu\n", (unsigned long long)end_seq - (unsigned long)max_seq, - (unsigned long long)msk->rcv_wnd_sent); + (unsigned long long)atomic64_read(&msk->rcv_wnd_sent)); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_NODSSWINDOW); return; } @@ -3004,7 +3004,7 @@ struct sock *mptcp_sk_clone(const struct sock *sk, mptcp_crypto_key_sha(msk->remote_key, NULL, &ack_seq); ack_seq++; WRITE_ONCE(msk->ack_seq, ack_seq); - WRITE_ONCE(msk->rcv_wnd_sent, ack_seq); + atomic64_set(&msk->rcv_wnd_sent, ack_seq); } sock_reset_flag(nsk, SOCK_RCU_FREE); @@ -3297,9 +3297,9 @@ void mptcp_finish_connect(struct sock *ssk) WRITE_ONCE(msk->write_seq, subflow->idsn + 1); WRITE_ONCE(msk->snd_nxt, msk->write_seq); WRITE_ONCE(msk->ack_seq, ack_seq); - WRITE_ONCE(msk->rcv_wnd_sent, ack_seq); WRITE_ONCE(msk->can_ack, 1); WRITE_ONCE(msk->snd_una, msk->write_seq); + atomic64_set(&msk->rcv_wnd_sent, ack_seq); mptcp_pm_new_connection(msk, ssk, 0); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index f542aeaa5b09..4672901d0dfe 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -257,7 +257,7 @@ struct mptcp_sock { u64 write_seq; u64 snd_nxt; u64 ack_seq; - u64 rcv_wnd_sent; + atomic64_t rcv_wnd_sent; u64 rcv_data_fin_seq; int rmem_fwd_alloc; struct sock *last_snd; -- cgit v1.2.3