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To solve this problem, I updated the function `tcp_drop(struct sock *sk, struct sk_buff *skb, int field, const char *reason)`. This way you can understand the reason for the deletion based on the prompt message. `field`: represents the SNMP-related value `reason`: represents the reason why `tcp` deleted the current `skb`, and contains some hints. Of course, if you want to know more about the reason for updating the current function, you can check: https://www.brendangregg.com/blog/2018-05-31/linux-tcpdrop.html Signed-off-by: Zhongya Yan --- include/trace/events/tcp.h | 62 ++++++++++++++++++ net/ipv4/tcp_input.c | 126 +++++++++++++++++++++++-------------- 2 files changed, 142 insertions(+), 46 deletions(-) diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h index 521059d8dc0a..68bbe8741ce8 100644 --- a/include/trace/events/tcp.h +++ b/include/trace/events/tcp.h @@ -371,6 +371,68 @@ DEFINE_EVENT(tcp_event_skb, tcp_bad_csum, TP_ARGS(skb) ); +TRACE_EVENT(tcp_drop, + TP_PROTO(struct sock *sk, struct sk_buff *skb, int field, const char *reason), + + TP_ARGS(sk, skb, field, 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(int, field) + __string(reason, 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->field = field; + + __assign_str(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 field=%d 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->field, __get_str(reason)) +); + #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 3f7bd7ae7d7a..1cebdcafb00f 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4675,8 +4675,10 @@ static bool tcp_ooo_try_coalesce(struct sock *sk, return res; } -static void tcp_drop(struct sock *sk, struct sk_buff *skb) +static void tcp_drop(struct sock *sk, struct sk_buff *skb, + int field, const char *reason) { + trace_tcp_drop(sk, skb, field, reason); sk_drops_add(sk, skb); __kfree_skb(skb); } @@ -4708,7 +4710,7 @@ static void tcp_ofo_queue(struct sock *sk) rb_erase(&skb->rbnode, &tp->out_of_order_queue); if (unlikely(!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))) { - tcp_drop(sk, skb); + tcp_drop(sk, skb, LINUX_MIB_TCPOFOQUEUE, "TCP queue error"); continue; } @@ -4764,7 +4766,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) { NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFODROP); sk->sk_data_ready(sk); - tcp_drop(sk, skb); + tcp_drop(sk, skb, LINUX_MIB_TCPOFODROP, "TCP rmem failed"); return; } @@ -4827,7 +4829,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) /* All the bits are present. Drop. */ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOMERGE); - tcp_drop(sk, skb); + tcp_drop(sk, skb, LINUX_MIB_TCPOFOMERGE, "TCP bits are present"); skb = NULL; tcp_dsack_set(sk, seq, end_seq); goto add_sack; @@ -4846,7 +4848,9 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) TCP_SKB_CB(skb1)->end_seq); NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOMERGE); - tcp_drop(sk, skb1); + tcp_drop(sk, skb1, LINUX_MIB_TCPOFOMERGE, + "TCP replace(skb.seq eq skb1.seq)"); + goto merge_right; } } else if (tcp_ooo_try_coalesce(sk, skb1, @@ -4874,7 +4878,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq); NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOMERGE); - tcp_drop(sk, skb1); + tcp_drop(sk, skb1, LINUX_MIB_TCPOFOMERGE, "TCP useless other segments"); } /* If there is no skb after us, we are the last_skb ! */ if (!skb1) @@ -5010,7 +5014,8 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) else if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) { NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP); sk->sk_data_ready(sk); - goto drop; + tcp_drop(sk, skb, LINUX_MIB_TCPRCVQDROP, "TCP rmem failed"); + goto end; } eaten = tcp_queue_rcv(sk, skb, &fragstolen); @@ -5050,8 +5055,8 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) out_of_window: tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS); inet_csk_schedule_ack(sk); -drop: - tcp_drop(sk, skb); + tcp_drop(sk, skb, LINUX_MIB_TCPZEROWINDOWDROP, "TCP out of order or zero window"); +end: return; } @@ -5308,7 +5313,7 @@ static bool tcp_prune_ofo_queue(struct sock *sk) prev = rb_prev(node); rb_erase(node, &tp->out_of_order_queue); goal -= rb_to_skb(node)->truesize; - tcp_drop(sk, rb_to_skb(node)); + tcp_drop(sk, rb_to_skb(node), LINUX_MIB_OFOPRUNED, "TCP drop out-of-order queue"); if (!prev || goal <= 0) { sk_mem_reclaim(sk); if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf && @@ -5643,7 +5648,8 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, LINUX_MIB_TCPACKSKIPPEDPAWS, &tp->last_oow_ack_time)) tcp_send_dupack(sk, skb); - goto discard; + tcp_drop(sk, skb, LINUX_MIB_PAWSESTABREJECTED, "TCP PAWS seq first"); + goto end; } /* Reset is accepted even if it did not pass PAWS. */ } @@ -5666,7 +5672,8 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, } else if (tcp_reset_check(sk, skb)) { tcp_reset(sk, skb); } - goto discard; + tcp_drop(sk, skb, LINUX_MIB_PAWSESTABREJECTED, "TCP check sequence number"); + goto end; } /* Step 2: check RST bit */ @@ -5711,7 +5718,8 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, tcp_fastopen_active_disable(sk); tcp_send_challenge_ack(sk, skb); } - goto discard; + tcp_drop(sk, skb, LINUX_MIB_TCPCHALLENGEACK, "TCP check RST bit "); + goto end; } /* step 3: check security and precedence [ignored] */ @@ -5725,15 +5733,15 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS); NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE); tcp_send_challenge_ack(sk, skb); - goto discard; + tcp_drop(sk, skb, LINUX_MIB_TCPSYNCHALLENGE, "TCP check for a SYN"); + goto end; } bpf_skops_parse_hdr(sk, skb); return true; -discard: - tcp_drop(sk, skb); +end: return false; } @@ -5851,7 +5859,8 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb) return; } else { /* Header too small */ TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS); - goto discard; + tcp_drop(sk, skb, TCP_MIB_INERRS, "TCP header too small"); + goto end; } } else { int eaten = 0; @@ -5905,8 +5914,10 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb) if (len < (th->doff << 2) || tcp_checksum_complete(skb)) goto csum_error; - if (!th->ack && !th->rst && !th->syn) - goto discard; + if (!th->ack && !th->rst && !th->syn) { + tcp_drop(sk, skb, LINUX_MIB_TCPSLOWSTARTRETRANS, "TCP state not in ack|rst|syn"); + goto end; + } /* * Standard slow path. @@ -5916,8 +5927,10 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb) return; step5: - if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0) - goto discard; + if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0) { + tcp_drop(sk, skb, LINUX_MIB_TCPSACKDISCARD, "TCP ack have not sent yet"); + goto end; + } tcp_rcv_rtt_measure_ts(sk, skb); @@ -5935,9 +5948,10 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb) trace_tcp_bad_csum(skb); TCP_INC_STATS(sock_net(sk), TCP_MIB_CSUMERRORS); TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS); + tcp_drop(sk, skb, TCP_MIB_CSUMERRORS, "TCP csum error"); -discard: - tcp_drop(sk, skb); +end: + return; } EXPORT_SYMBOL(tcp_rcv_established); @@ -6137,7 +6151,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, if (th->rst) { tcp_reset(sk, skb); - goto discard; + tcp_drop(sk, skb, LINUX_MIB_NUM, "TCP reset"); + goto end; } /* rfc793: @@ -6226,9 +6241,9 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS); inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, TCP_DELACK_MAX, TCP_RTO_MAX); + tcp_drop(sk, skb, LINUX_MIB_TCPFASTOPENACTIVE, "TCP fast open ack error"); -discard: - tcp_drop(sk, skb); +end: return 0; } else { tcp_send_ack(sk); @@ -6301,7 +6316,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, */ return -1; #else - goto discard; + tcp_drop(sk, skb, LINUX_MIB_SYNCOOKIESRECV, "TCP syn received error"); + goto end; #endif } /* "fifth, if neither of the SYN or RST bits is set then @@ -6311,7 +6327,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, discard_and_undo: tcp_clear_options(&tp->rx_opt); tp->rx_opt.mss_clamp = saved_clamp; - goto discard; + tcp_drop(sk, skb, LINUX_MIB_TCPSACKDISCARD, "TCP not neither of SYN or RST"); + goto end; reset_and_undo: tcp_clear_options(&tp->rx_opt); @@ -6369,18 +6386,23 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) switch (sk->sk_state) { case TCP_CLOSE: - goto discard; + tcp_drop(sk, skb, LINUX_MIB_TCPABORTONCLOSE, "TCP close"); + goto end; case TCP_LISTEN: if (th->ack) return 1; - if (th->rst) - goto discard; + if (th->rst) { + tcp_drop(sk, skb, LINUX_MIB_LISTENDROPS, "TCP rst"); + goto end; + } if (th->syn) { - if (th->fin) - goto discard; + if (th->fin) { + tcp_drop(sk, skb, LINUX_MIB_LISTENDROPS, "TCP fin"); + goto end; + } /* It is possible that we process SYN packets from backlog, * so we need to make sure to disable BH and RCU right there. */ @@ -6395,7 +6417,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) consume_skb(skb); return 0; } - goto discard; + tcp_drop(sk, skb, LINUX_MIB_LISTENDROPS, "TCP syn"); + goto end; case TCP_SYN_SENT: tp->rx_opt.saw_tstamp = 0; @@ -6421,12 +6444,16 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && sk->sk_state != TCP_FIN_WAIT1); - if (!tcp_check_req(sk, skb, req, true, &req_stolen)) - goto discard; + if (!tcp_check_req(sk, skb, req, true, &req_stolen)) { + tcp_drop(sk, skb, LINUX_MIB_LISTENDROPS, "TCP check req error"); + goto end; + } } - if (!th->ack && !th->rst && !th->syn) - goto discard; + if (!th->ack && !th->rst && !th->syn) { + tcp_drop(sk, skb, LINUX_MIB_LISTENDROPS, "TCP not ack|rst|syn"); + goto end; + } if (!tcp_validate_incoming(sk, skb, th, 0)) return 0; @@ -6440,7 +6467,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) if (sk->sk_state == TCP_SYN_RECV) return 1; /* send one RST */ tcp_send_challenge_ack(sk, skb); - goto discard; + tcp_drop(sk, skb, LINUX_MIB_TCPCHALLENGEACK, "TCP check ack failed"); + goto end; } switch (sk->sk_state) { case TCP_SYN_RECV: @@ -6533,7 +6561,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) inet_csk_reset_keepalive_timer(sk, tmo); } else { tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); - goto discard; + tcp_drop(sk, skb, LINUX_MIB_TCPABORTONDATA, "TCP fin wait2"); + goto end; } break; } @@ -6541,7 +6570,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) case TCP_CLOSING: if (tp->snd_una == tp->write_seq) { tcp_time_wait(sk, TCP_TIME_WAIT, 0); - goto discard; + tcp_drop(sk, skb, LINUX_MIB_TIMEWAITED, "TCP time wait"); + goto end; } break; @@ -6549,7 +6579,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) if (tp->snd_una == tp->write_seq) { tcp_update_metrics(sk); tcp_done(sk); - goto discard; + tcp_drop(sk, skb, LINUX_MIB_TCPPUREACKS, "TCP last ack"); + goto end; } break; } @@ -6566,8 +6597,10 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) /* If a subflow has been reset, the packet should not * continue to be processed, drop the packet. */ - if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb)) - goto discard; + if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb)) { + tcp_drop(sk, skb, LINUX_MIB_TCPPUREACKS, "TCP subflow been reset"); + goto end; + } break; } fallthrough; @@ -6599,9 +6632,10 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) } if (!queued) { -discard: - tcp_drop(sk, skb); + tcp_drop(sk, skb, LINUX_MIB_TCPOFOQUEUE, "TCP rcv synsent state process"); } + +end: return 0; } EXPORT_SYMBOL(tcp_rcv_state_process);