Re: [PATCH] net: tcp_drop adds `reason` parameter for tracing
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2021-08-24 15:30:08
Also in:
lkml
On Tue, 24 Aug 2021 05:51:40 -0700 Zhongya Yan [off-list ref] wrote:
quoted hunk ↗ jump to hunk
When using `tcp_drop(struct sock *sk, struct sk_buff *skb)` we can not tell why we need to delete `skb`. To solve this problem I updated the method `tcp_drop(struct sock *sk, struct sk_buff *skb, enum tcp_drop_reason reason)` to include the source of the deletion when it is done, so you can get an idea of the reason for the deletion based on the source. The current purpose is mainly derived from the suggestions of `Yonghong Song` and `brendangregg`: https://github.com/iovisor/bcc/issues/3533. "It is worthwhile to mention the context/why we want to this tracepoint with bcc issue https://github.com/iovisor/bcc/issues/3533. Mainly two reasons: (1). tcp_drop is a tiny function which may easily get inlined, a tracepoint is more stable, and (2). tcp_drop does not provide enough information on why it is dropped. " by Yonghong Song Signed-off-by: Zhongya Yan <redacted> --- include/net/tcp.h | 11 ++++++++ include/trace/events/tcp.h | 56 ++++++++++++++++++++++++++++++++++++++ net/ipv4/tcp_input.c | 34 +++++++++++++++-------- 3 files changed, 89 insertions(+), 12 deletions(-)diff --git a/include/net/tcp.h b/include/net/tcp.h index 784d5c3ef1c5..dd8cd8d6f2f1 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h@@ -254,6 +254,17 @@ extern atomic_long_t tcp_memory_allocated; extern struct percpu_counter tcp_sockets_allocated; extern unsigned long tcp_memory_pressure; +enum tcp_drop_reason { + TCP_OFO_QUEUE = 1, + TCP_DATA_QUEUE_OFO = 2, + TCP_DATA_QUEUE = 3, + TCP_PRUNE_OFO_QUEUE = 4, + TCP_VALIDATE_INCOMING = 5, + TCP_RCV_ESTABLISHED = 6, + TCP_RCV_SYNSENT_STATE_PROCESS = 7, + TCP_RCV_STATE_PROCESS = 8
As enums increase by one, you could save yourself the burden of
updating the numbers and just have:
enum tcp_drop_reason {
TCP_OFO_QUEUE = 1,
TCP_DATA_QUEUE_OFO,
TCP_DATA_QUEUE,
TCP_PRUNE_OFO_QUEUE,
TCP_VALIDATE_INCOMING,
TCP_RCV_ESTABLISHED,
TCP_RCV_SYNSENT_STATE_PROCESS,
TCP_RCV_STATE_PROCESS
};
Which would do the same.
quoted hunk ↗ jump to hunk
+}; + /* optimized version of sk_under_memory_pressure() for TCP sockets */ static inline bool tcp_under_memory_pressure(const struct sock *sk) {diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h index 521059d8dc0a..a0d3d31eb591 100644 --- a/include/trace/events/tcp.h +++ b/include/trace/events/tcp.h@@ -371,6 +371,62 @@ DEFINE_EVENT(tcp_event_skb, tcp_bad_csum, TP_ARGS(skb) );
If you would like to see the english translation of what these
"reasons" are and not have to remember which number is which, you can
do the following:
#define TCP_DROP_REASON \
EM(TCP_OFO_QUEUE, ofo_queue) \
EM(TCP_DATA_QUEUE_OFO, data_queue_ofo) \
EM(TCP_DATA_QUEUE, data_queue) \
EM(TCP_PRUNE_OFO_QUEUE, prune_ofo_queue) \
EM(TCP_VALIDATE_INCOMING, validate_incoming) \
EM(TCP_RCV_ESTABLISHED, rcv_established) \
EM(TCP_RCV_SYNSENT_STATE_PROCESS, rcv_synsent_state_process) \
EMe(TCP_RCV_STATE_PROCESS, rcv_state_proces)
#undef EM
#undef EMe
#define EM(a,b) { a, #b },
#define EMe(a, b) { a, #b }
+TRACE_EVENT(tcp_drop,
+ TP_PROTO(struct sock *sk, struct sk_buff *skb, enum tcp_drop_reason reason),
+
+ TP_ARGS(sk, skb, reason),
+
+ TP_STRUCT__entry(
+ __array(__u8, saddr, sizeof(struct sockaddr_in6))
+ __array(__u8, daddr, sizeof(struct sockaddr_in6))
+ __field(__u16, sport)
+ __field(__u16, dport)
+ __field(__u32, mark)
+ __field(__u16, data_len)
+ __field(__u32, snd_nxt)
+ __field(__u32, snd_una)
+ __field(__u32, snd_cwnd)
+ __field(__u32, ssthresh)
+ __field(__u32, snd_wnd)
+ __field(__u32, srtt)
+ __field(__u32, rcv_wnd)
+ __field(__u64, sock_cookie)
+ __field(__u32, reason)
+ ),
+
+ TP_fast_assign(
+ const struct tcphdr *th = (const struct tcphdr *)skb->data;
+ const struct inet_sock *inet = inet_sk(sk);
+ const struct tcp_sock *tp = tcp_sk(sk);
+
+ memset(__entry->saddr, 0, sizeof(struct sockaddr_in6));
+ memset(__entry->daddr, 0, sizeof(struct sockaddr_in6));
+
+ TP_STORE_ADDR_PORTS(__entry, inet, sk);
+
+ __entry->sport = ntohs(inet->inet_sport);
+ __entry->dport = ntohs(inet->inet_dport);
+ __entry->mark = skb->mark;
+
+ __entry->data_len = skb->len - __tcp_hdrlen(th);
+ __entry->snd_nxt = tp->snd_nxt;
+ __entry->snd_una = tp->snd_una;
+ __entry->snd_cwnd = tp->snd_cwnd;
+ __entry->snd_wnd = tp->snd_wnd;
+ __entry->rcv_wnd = tp->rcv_wnd;
+ __entry->ssthresh = tcp_current_ssthresh(sk);
+ __entry->srtt = tp->srtt_us >> 3;
+ __entry->sock_cookie = sock_gen_cookie(sk);
+ __entry->reason = reason;
+ ),
+
+ TP_printk("src=%pISpc dest=%pISpc mark=%#x data_len=%d snd_nxt=%#x snd_una=%#x snd_cwnd=%u ssthresh=%u snd_wnd=%u srtt=%u rcv_wnd=%u sock_cookie=%llx reason=%d",Then above you can have: "reason=%s"
+ __entry->saddr, __entry->daddr, __entry->mark, + __entry->data_len, __entry->snd_nxt, __entry->snd_una, + __entry->snd_cwnd, __entry->ssthresh, __entry->snd_wnd, + __entry->srtt, __entry->rcv_wnd, __entry->sock_cookie, __entry->reason)
And here: __print_symbolic(__entry->reason, TCP_DROP_REASON) -- Steve
+); + #endif /* _TRACE_TCP_H */ /* This part must be outside protection */