On Thu, Oct 12, 2017 at 4:18 PM, Alexei Starovoitov <alexei.starovoi...@gmail.com> wrote: > On Thu, Oct 12, 2017 at 03:48:07PM -0700, Cong Wang wrote: >> 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 <eduma...@google.com> >> Cc: Alexei Starovoitov <alexei.starovoi...@gmail.com> >> Cc: Hannes Frederic Sowa <han...@stressinduktion.org> >> Cc: Brendan Gregg <brendan.d.gr...@gmail.com> >> Cc: Neal Cardwell <ncardw...@google.com> >> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com> >> --- >> include/trace/events/tcp.h | 68 >> ++++++++++++++++++++++++++++++++++++++++++++++ >> net/core/net-traces.c | 1 + >> net/ipv4/tcp_output.c | 3 ++ >> 3 files changed, 72 insertions(+) >> create mode 100644 include/trace/events/tcp.h >> >> diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h >> new file mode 100644 >> index 000000000000..749f93c542ab >> --- /dev/null >> +++ b/include/trace/events/tcp.h >> @@ -0,0 +1,68 @@ >> +#undef TRACE_SYSTEM >> +#define TRACE_SYSTEM tcp >> + >> +#if !defined(_TRACE_TCP_H) || defined(TRACE_HEADER_MULTI_READ) >> +#define _TRACE_TCP_H >> + >> +#include <linux/ipv6.h> >> +#include <linux/tcp.h> >> +#include <linux/tracepoint.h> >> +#include <net/ipv6.h> >> + >> +TRACE_EVENT(tcp_retransmit_skb, >> + >> + TP_PROTO(struct sock *sk, struct sk_buff *skb, int segs), >> + >> + TP_ARGS(sk, skb, segs), >> + >> + TP_STRUCT__entry( >> + __field(void *, skbaddr) >> + __field(void *, skaddr) >> + __field(__u16, sport) >> + __field(__u16, dport) >> + __array(__u8, saddr, 4) >> + __array(__u8, daddr, 4) >> + __array(__u8, saddr_v6, 16) >> + __array(__u8, daddr_v6, 16) >> + ), > ... >> if (likely(!err)) { >> TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS; >> + trace_tcp_retransmit_skb(sk, skb, segs); > > looks great to me, but why 'segs' is there? > It's unused.
Ah, I copy-n-paste the tcp_retransmit_skb() prototype... I will remove it. Thanks.
