• Cong Wang's avatar
    tcp: add a tracepoint for tcp retransmission · e086101b
    Cong Wang authored
    We need a real-time notification for tcp retransmission
    for monitoring.
    
    Of course we could use ftrace to dynamically instrument this
    kernel function too, however we can't retrieve the connection
    information at the same time, for example perf-tools [1] reads
    /proc/net/tcp for socket details, which is slow when we have
    a lots of connections.
    
    Therefore, this patch adds a tracepoint for __tcp_retransmit_skb()
    and exposes src/dst IP addresses and ports of the connection.
    This also makes it easier to integrate into perf.
    
    Note, I expose both IPv4 and IPv6 addresses at the same time:
    for a IPv4 socket, v4 mapped address is used as IPv6 addresses,
    for a IPv6 socket, LOOPBACK4_IPV6 is already filled by kernel.
    Also, add sk and skb pointers as they are useful for BPF.
    
    1. https://github.com/brendangregg/perf-tools/blob/master/net/tcpretrans
    
    Cc: Eric Dumazet <edumazet@google.com>
    Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
    Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
    Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
    Cc: Neal Cardwell <ncardwell@google.com>
    Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
    Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Acked-by: default avatarBrendan Gregg <bgregg@netflix.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    e086101b
tcp_output.c 107 KB