• Eric Dumazet's avatar
    tcp: dont drop MTU reduction indications · 563d34d0
    Eric Dumazet authored
    ICMP messages generated in output path if frame length is bigger than
    mtu are actually lost because socket is owned by user (doing the xmit)
    One example is the ipgre_tunnel_xmit() calling
    icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
    We had a similar case fixed in commit a34a101e (ipv6: disable GSO on
    sockets hitting dst_allfrag).
    Problem of such fix is that it relied on retransmit timers, so short tcp
    sessions paid a too big latency increase price.
    This patch uses the tcp_release_cb() infrastructure so that MTU
    reduction messages (ICMP messages) are not lost, and no extra delay
    is added in TCP transmits.
    Reported-by: default avatarMaciej Żenczykowski <maze@google.com>
    Diagnosed-by: default avatarNeal Cardwell <ncardwell@google.com>
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Cc: Nandita Dukkipati <nanditad@google.com>
    Cc: Tom Herbert <therbert@google.com>
    Cc: Tore Anderson <tore@fud.no>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
sock.h 61 KB