From ab67d804132ce5a134037b637c6d186bfc583ad0 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Thu, 15 Oct 2020 05:20:27 +0000 Subject: [PATCH] tcp: propagate MPTCP skb extensions on xmit splits When the TCP stack splits a packet on the write queue, the tail half currently lose the associated skb extensions, and will not carry the DSM on the wire. The above does not cause functional problems and is allowed by the RFC, but interact badly with GRO and RX coalescing, as possible candidates for aggregation will carry different TCP options. This change tries to improve the MPTCP behavior, propagating the skb extensions on split. Additionally, we must prevent the MPTCP stack from updating the mapping after the split occur: that will both violate the RFC and fool the reader. Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni --- include/net/mptcp.h | 21 ++++++++++++++++++++- net/ipv4/tcp_output.c | 3 +++ net/mptcp/protocol.c | 7 +++++-- 3 files changed, 28 insertions(+), 3 deletions(-) diff --git a/include/net/mptcp.h b/include/net/mptcp.h index 753ba7e755d6d..6e706d838e4eb 100644 --- a/include/net/mptcp.h +++ b/include/net/mptcp.h @@ -29,7 +29,8 @@ struct mptcp_ext { use_ack:1, ack64:1, mpc_map:1, - __unused:2; + frozen:1, + __unused:1; /* one byte hole */ }; @@ -106,6 +107,19 @@ static inline void mptcp_skb_ext_move(struct sk_buff *to, from->active_extensions = 0; } +static inline void mptcp_skb_ext_copy(struct sk_buff *to, + struct sk_buff *from) +{ + struct mptcp_ext *from_ext; + + from_ext = skb_ext_find(from, SKB_EXT_MPTCP); + if (!from_ext) + return; + + from_ext->frozen = 1; + skb_ext_copy(to, from); +} + static inline bool mptcp_ext_matches(const struct mptcp_ext *to_ext, const struct mptcp_ext *from_ext) { @@ -193,6 +207,11 @@ static inline void mptcp_skb_ext_move(struct sk_buff *to, { } +static inline void mptcp_skb_ext_copy(struct sk_buff *to, + struct sk_buff *from) +{ +} + static inline bool mptcp_skb_can_collapse(const struct sk_buff *to, const struct sk_buff *from) { diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index bf48cd73e9678..9abf5a0358d54 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1569,6 +1569,7 @@ int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue, if (!buff) return -ENOMEM; /* We'll just try again later. */ skb_copy_decrypted(buff, skb); + mptcp_skb_ext_copy(buff, skb); sk_wmem_queued_add(sk, buff->truesize); sk_mem_charge(sk, buff->truesize); @@ -2123,6 +2124,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, if (unlikely(!buff)) return -ENOMEM; skb_copy_decrypted(buff, skb); + mptcp_skb_ext_copy(buff, skb); sk_wmem_queued_add(sk, buff->truesize); sk_mem_charge(sk, buff->truesize); @@ -2393,6 +2395,7 @@ static int tcp_mtu_probe(struct sock *sk) skb = tcp_send_head(sk); skb_copy_decrypted(nskb, skb); + mptcp_skb_ext_copy(nskb, skb); TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 625054b4d9488..f35a6fe973734 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -761,8 +761,11 @@ static bool mptcp_skb_can_collapse_to(u64 write_seq, if (!tcp_skb_can_collapse_to(skb)) return false; - /* can collapse only if MPTCP level sequence is in order */ - return mpext && mpext->data_seq + mpext->data_len == write_seq; + /* can collapse only if MPTCP level sequence is in order and this + * mapping has not been xmitted yet + */ + return mpext && mpext->data_seq + mpext->data_len == write_seq && + !mpext->frozen; } static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,