On 2024-03-11 at 08:11:04, Jason Xing (kerneljasonx...@gmail.com) wrote:
> From: Jason Xing <kernelx...@tencent.com>
>
> Prior to this patch, what we can see by enabling trace_tcp_send is
> only happening under two circumstances:
> 1) active rst mode
> 2) non-active rst mode and based on the full socket
>
> That means the inconsistency occurs if we use tcpdump and trace
> simultaneously to see how rst happens.
>
> It's necessary that we should take into other cases into considerations,
> say:
> 1) time-wait socket
> 2) no socket
> ...
>
> By parsing the incoming skb and reversing its 4-turple can
> we know the exact 'flow' which might not exist.
>
> Samples after applied this patch:
> 1. tcp_send_reset: skbaddr=XXX skaddr=XXX src=ip:port dest=ip:port
> state=TCP_ESTABLISHED
> 2. tcp_send_reset: skbaddr=000...000 skaddr=XXX src=ip:port dest=ip:port
> state=UNKNOWN
> Note:
> 1) UNKNOWN means we cannot extract the right information from skb.
> 2) skbaddr/skaddr could be 0
>
> Signed-off-by: Jason Xing <kernelx...@tencent.com>
> ---
> include/trace/events/tcp.h | 39 ++++++++++++++++++++++++++++++++++++--
> net/ipv4/tcp_ipv4.c | 4 ++--
> net/ipv6/tcp_ipv6.c | 3 ++-
> 3 files changed, 41 insertions(+), 5 deletions(-)
>
> diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
> index 2495a1d579be..6c09d7941583 100644
> --- a/include/trace/events/tcp.h
> +++ b/include/trace/events/tcp.h
> @@ -107,11 +107,46 @@ DEFINE_EVENT(tcp_event_sk_skb, tcp_retransmit_skb,
> * skb of trace_tcp_send_reset is the skb that caused RST. In case of
> * active reset, skb should be NULL
> */
> -DEFINE_EVENT(tcp_event_sk_skb, tcp_send_reset,
> +TRACE_EVENT(tcp_send_reset,
>
> TP_PROTO(const struct sock *sk, const struct sk_buff *skb),
>
> - TP_ARGS(sk, skb)
> + TP_ARGS(sk, skb),
> +
> + TP_STRUCT__entry(
> + __field(const void *, skbaddr)
> + __field(const void *, skaddr)
> + __field(int, state)
> + __array(__u8, saddr, sizeof(struct sockaddr_in6))
> + __array(__u8, daddr, sizeof(struct sockaddr_in6))
> + ),
> +
> + TP_fast_assign(
> + __entry->skbaddr = skb;
> + __entry->skaddr = sk;
> + /* Zero means unknown state. */
> + __entry->state = sk ? sk->sk_state : 0;
> +
> + memset(__entry->saddr, 0, sizeof(struct sockaddr_in6));
> + memset(__entry->daddr, 0, sizeof(struct sockaddr_in6));
> +
> + if (sk && sk_fullsock(sk)) {
> + const struct inet_sock *inet = inet_sk(sk);
> +
> + TP_STORE_ADDR_PORTS(__entry, inet, sk);
> + } else {
> + /*
> + * We should reverse the 4-turple of skb, so later
> + * it can print the right flow direction of rst.
> + */
> + TP_STORE_ADDR_PORTS_SKB(skb, entry->daddr,
> entry->saddr);
> + }
> + ),
> +
> + TP_printk("skbaddr=%p skaddr=%p src=%pISpc dest=%pISpc state=%s",
Could you consider using %px ? is it permitted ? it will be easy to track skb.
> + __entry->skbaddr, __entry->skaddr,
> + __entry->saddr, __entry->daddr,
> + __entry->state ? show_tcp_state_name(__entry->state) :
> "UNKNOWN")
> );
>
> /*
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index a22ee5838751..d5c4a969c066 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -868,10 +868,10 @@ static void tcp_v4_send_reset(const struct sock *sk,
> struct sk_buff *skb)
> */
> if (sk) {
> arg.bound_dev_if = sk->sk_bound_dev_if;
> - if (sk_fullsock(sk))
> - trace_tcp_send_reset(sk, skb);
> }
>
> + trace_tcp_send_reset(sk, skb);
> +
> BUILD_BUG_ON(offsetof(struct sock, sk_bound_dev_if) !=
> offsetof(struct inet_timewait_sock, tw_bound_dev_if));
>
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 3f4cba49e9ee..8e9c59b6c00c 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1113,7 +1113,6 @@ static void tcp_v6_send_reset(const struct sock *sk,
> struct sk_buff *skb)
> if (sk) {
> oif = sk->sk_bound_dev_if;
> if (sk_fullsock(sk)) {
> - trace_tcp_send_reset(sk, skb);
> if (inet6_test_bit(REPFLOW, sk))
> label = ip6_flowlabel(ipv6h);
> priority = READ_ONCE(sk->sk_priority);
> @@ -1129,6 +1128,8 @@ static void tcp_v6_send_reset(const struct sock *sk,
> struct sk_buff *skb)
> label = ip6_flowlabel(ipv6h);
> }
>
> + trace_tcp_send_reset(sk, skb);
> +
> tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, 1,
> ipv6_get_dsfield(ipv6h), label, priority, txhash,
> &key);
> --
> 2.37.3
>
