Messages in this thread | | | From | Eric Dumazet <> | Date | Sun, 15 May 2022 21:22:20 -0700 | Subject | Re: [PATCH net-next 8/9] net: tcp: add skb drop reasons to tcp tw code path |
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On Sun, May 15, 2022 at 8:46 PM <menglong8.dong@gmail.com> wrote: > > From: Menglong Dong <imagedong@tencent.com> > > In order to get the reasons of skb drops, add a function argument of > type 'enum skb_drop_reason *reason' to tcp_timewait_state_process(). > > In the origin code, all packets to time-wait socket are treated as > dropping with kfree_skb(), which can make users confused. Therefore, > we use consume_skb() for the skbs that are 'good'. We can check the > value of 'reason' to decide use kfree_skb() or consume_skb(). > > The new reason 'TIMEWAIT' is added for the case that the skb is dropped > as the socket in time-wait state. > > Signed-off-by: Menglong Dong <imagedong@tencent.com> > --- > include/linux/skbuff.h | 5 +++++ > include/net/tcp.h | 7 ++++--- > net/ipv4/tcp_ipv4.c | 11 +++++++++-- > net/ipv4/tcp_minisocks.c | 24 ++++++++++++++++++++---- > net/ipv6/tcp_ipv6.c | 10 ++++++++-- > 5 files changed, 46 insertions(+), 11 deletions(-) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 4578bbab5a3e..8d18fc5a5af6 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -560,6 +560,10 @@ struct sk_buff; > * SKB_DROP_REASON_TCP_REQQFULLDROP > * request queue of the listen socket is full, corresponding to > * LINUX_MIB_TCPREQQFULLDROP > + * > + * SKB_DROP_REASON_TIMEWAIT > + * socket is in time-wait state and all packet that received will > + * be treated as 'drop', except a good 'SYN' packet > */ > #define __DEFINE_SKB_DROP_REASON(FN) \ > FN(NOT_SPECIFIED) \ > @@ -631,6 +635,7 @@ struct sk_buff; > FN(TCP_ABORTONDATA) \ > FN(LISTENOVERFLOWS) \ > FN(TCP_REQQFULLDROP) \ > + FN(TIMEWAIT) \ > FN(MAX) > > /* The reason of skb drop, which is used in kfree_skb_reason(). > diff --git a/include/net/tcp.h b/include/net/tcp.h > index 082dd0627e2e..88217b8d95ac 100644 > --- a/include/net/tcp.h > +++ b/include/net/tcp.h > @@ -380,9 +380,10 @@ enum tcp_tw_status { > }; > > > -enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw, > - struct sk_buff *skb, > - const struct tcphdr *th); > +enum tcp_tw_status > +tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, > + const struct tcphdr *th, > + enum skb_drop_reason *reason); > struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, > struct request_sock *req, bool fastopen, > bool *lost_race); > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c > index 708f92b03f42..9174ee162633 100644 > --- a/net/ipv4/tcp_ipv4.c > +++ b/net/ipv4/tcp_ipv4.c > @@ -2134,7 +2134,8 @@ int tcp_v4_rcv(struct sk_buff *skb) > inet_twsk_put(inet_twsk(sk)); > goto csum_error; > } > - switch (tcp_timewait_state_process(inet_twsk(sk), skb, th)) { > + switch (tcp_timewait_state_process(inet_twsk(sk), skb, th, > + &drop_reason)) { > case TCP_TW_SYN: { > struct sock *sk2 = inet_lookup_listener(dev_net(skb->dev), > &tcp_hashinfo, skb, > @@ -2150,12 +2151,18 @@ int tcp_v4_rcv(struct sk_buff *skb) > refcounted = false; > goto process; > } > + /* TCP_FLAGS or NO_SOCKET? */ > + SKB_DR_SET(drop_reason, TCP_FLAGS); > } > /* to ACK */ > fallthrough; > case TCP_TW_ACK: > tcp_v4_timewait_ack(sk, skb); > - break; > + refcounted = false; > + if (drop_reason) > + goto discard_it; > + else > + goto put_and_return; > case TCP_TW_RST: > tcp_v4_send_reset(sk, skb); > inet_twsk_deschedule_put(inet_twsk(sk)); > diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c > index 1a21018f6f64..329724118b7f 100644 > --- a/net/ipv4/tcp_minisocks.c > +++ b/net/ipv4/tcp_minisocks.c > @@ -83,13 +83,15 @@ tcp_timewait_check_oow_rate_limit(struct inet_timewait_sock *tw, > */ > enum tcp_tw_status > tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, > - const struct tcphdr *th) > + const struct tcphdr *th, > + enum skb_drop_reason *reason) > { > struct tcp_options_received tmp_opt; > struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw); > bool paws_reject = false; > > tmp_opt.saw_tstamp = 0; > + *reason = SKB_DROP_REASON_NOT_SPECIFIED; > if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) { > tcp_parse_options(twsk_net(tw), skb, &tmp_opt, 0, NULL); > > @@ -113,11 +115,16 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, > return tcp_timewait_check_oow_rate_limit( > tw, skb, LINUX_MIB_TCPACKSKIPPEDFINWAIT2); > > - if (th->rst) > + if (th->rst) { > + SKB_DR_SET(*reason, TCP_RESET); > goto kill; > + } > > - if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt)) > + if (th->syn && !before(TCP_SKB_CB(skb)->seq, > + tcptw->tw_rcv_nxt)) { > + SKB_DR_SET(*reason, TCP_FLAGS); > return TCP_TW_RST; > + } > > /* Dup ACK? */ > if (!th->ack || > @@ -143,6 +150,9 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, > } > > inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN); > + > + /* skb should be free normally on this case. */ > + *reason = SKB_NOT_DROPPED_YET; > return TCP_TW_ACK; > } > > @@ -174,6 +184,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, > * protocol bug yet. > */ > if (twsk_net(tw)->ipv4.sysctl_tcp_rfc1337 == 0) { > + SKB_DR_SET(*reason, TCP_RESET); > kill: > inet_twsk_deschedule_put(tw); > return TCP_TW_SUCCESS; > @@ -216,11 +227,14 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, > if (isn == 0) > isn++; > TCP_SKB_CB(skb)->tcp_tw_isn = isn; > + *reason = SKB_NOT_DROPPED_YET; > return TCP_TW_SYN; > } > > - if (paws_reject) > + if (paws_reject) { > + SKB_DR_SET(*reason, TCP_RFC7323_PAWS); > __NET_INC_STATS(twsk_net(tw), LINUX_MIB_PAWSESTABREJECTED); > + } > > if (!th->rst) { > /* In this case we must reset the TIMEWAIT timer. > @@ -232,9 +246,11 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, > if (paws_reject || th->ack) > inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN); > > + SKB_DR_OR(*reason, TIMEWAIT); > return tcp_timewait_check_oow_rate_limit( > tw, skb, LINUX_MIB_TCPACKSKIPPEDTIMEWAIT); > } > + SKB_DR_SET(*reason, TCP_RESET); > inet_twsk_put(tw); > return TCP_TW_SUCCESS; > } > diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c > index 27c51991bd54..5c777006de3d 100644 > --- a/net/ipv6/tcp_ipv6.c > +++ b/net/ipv6/tcp_ipv6.c > @@ -1795,7 +1795,8 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb) > goto csum_error; > } > > - switch (tcp_timewait_state_process(inet_twsk(sk), skb, th)) { > + switch (tcp_timewait_state_process(inet_twsk(sk), skb, th, > + &drop_reason)) { > case TCP_TW_SYN: > { > struct sock *sk2; > @@ -1815,12 +1816,17 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb) > refcounted = false; > goto process; > } > + SKB_DR_SET(drop_reason, TCP_FLAGS); > } > /* to ACK */ > fallthrough; > case TCP_TW_ACK: > tcp_v6_timewait_ack(sk, skb); > - break; > + refcounted = false; > + if (drop_reason) > + goto discard_it; > + else > + goto put_and_return;
My brain exploded. I guarantee you that whoever is going to look at this code in one year will be completely lost. Adding so much complexity is crazy.
About: refcounted = false ;
This is not going to be used id "goto discard_it;" is taken.
If the "goto put_and_return;" is taken, this boils down to:
return ret ? -1 : 0;
Are you sure ret is even initialized at this point ?
Why are we doing this ? We were doing "return 0;"
Also, where is skb freed ?
Are you calling tcp_v6_timewait_ack(sk, skb) after skb has been freed ???
> case TCP_TW_RST: > tcp_v6_send_reset(sk, skb); > inet_twsk_deschedule_put(inet_twsk(sk)); > -- > 2.36.1 >
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