Re: [PATCH] net: Add tcp_drop_reason tracepoint
From: Menglong Dong <hidden>
Date: 2024-10-23 12:59:43
Also in:
linux-trace-kernel
On Wed, Oct 23, 2024 at 8:33 PM Yafang Shao [off-list ref] wrote:
We previously hooked the tcp_drop_reason() function using BPF to monitor TCP drop reasons. However, after upgrading our compiler from GCC 9 to GCC 11, tcp_drop_reason() is now inlined, preventing us from hooking into it. To address this, it would be beneficial to introduce a dedicated tracepoint for monitoring.
Hello, Can the existing tracepoint kfree_skb do this work? AFAIK, you can attach you BPF to the kfree_skb tracepoint and do some filter according to the "protocol" field, or the information "sk" field. And this works fine in my tool. I hope I'm not missing something :/ BTW, I do such filter in probe_parse_skb_sk() in https://github.com/OpenCloudOS/nettrace/blob/master/shared/bpf/skb_parse.h Thanks! Menglong Dong
quoted hunk ↗ jump to hunk
Signed-off-by: Yafang Shao <redacted> Cc: Menglong Dong <redacted> --- include/trace/events/tcp.h | 53 ++++++++++++++++++++++++++++++++++++++ net/ipv4/tcp_input.c | 1 + 2 files changed, 54 insertions(+)diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h index a27c4b619dff..056f7026224c 100644 --- a/include/trace/events/tcp.h +++ b/include/trace/events/tcp.h@@ -12,6 +12,7 @@ #include <net/tcp.h> #include <linux/sock_diag.h> #include <net/rstreason.h> +#include <net/dropreason-core.h> /* * tcp event with arguments sk and skb@@ -728,6 +729,58 @@ DEFINE_EVENT(tcp_ao_event_sne, tcp_ao_rcv_sne_update, TP_ARGS(sk, new_sne) ); +#undef FN +#undef FNe +#define FN(reason) { SKB_DROP_REASON_##reason, #reason }, +#define FNe(reason) { SKB_DROP_REASON_##reason, #reason } + +TRACE_EVENT(tcp_drop_reason, + + TP_PROTO(const struct sock *sk, const struct sk_buff *skb, + const enum skb_drop_reason reason), + + TP_ARGS(sk, skb, reason), + + TP_STRUCT__entry( + __field(const void *, skbaddr) + __field(const void *, skaddr) + __field(int, state) + __field(enum skb_drop_reason, reason) + __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 { + const struct tcphdr *th = (const struct tcphdr *)skb->data; + + TP_STORE_ADDR_PORTS_SKB(skb, th, entry->saddr, entry->daddr); + } + __entry->reason = reason; + ), + + TP_printk("skbaddr=%p skaddr=%p src=%pISpc dest=%pISpc state=%s reason=%s", + __entry->skbaddr, __entry->skaddr, + __entry->saddr, __entry->daddr, + __entry->state ? show_tcp_state_name(__entry->state) : "UNKNOWN", + __print_symbolic(__entry->reason, DEFINE_DROP_REASON(FN, FNe))) +); + +#undef FN +#undef FNe + #endif /* _TRACE_TCP_H */ /* This part must be outside protection */diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index cc05ec1faac8..44795555596a 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c@@ -4897,6 +4897,7 @@ static bool tcp_ooo_try_coalesce(struct sock *sk, static void tcp_drop_reason(struct sock *sk, struct sk_buff *skb, enum skb_drop_reason reason) { + trace_tcp_drop_reason(sk, skb, reason); sk_drops_add(sk, skb); sk_skb_reason_drop(sk, skb, reason); } --2.43.5