Re: [PATCH net-next v2] tcp: Support skb PAWS drop reason when TIME-WAIT
From: Jiayuan Chen
Date: Tue Mar 25 2025 - 08:37:31 EST
March 25, 2025 at 19:29, "Eric Dumazet" <edumazet@xxxxxxxxxx> wrote:
> > ---
> >
> > include/net/tcp.h | 3 ++-
> >
> > net/ipv4/tcp_ipv4.c | 2 +-
> >
> > net/ipv4/tcp_minisocks.c | 7 +++++--
> >
> > net/ipv6/tcp_ipv6.c | 2 +-
> >
> > 4 files changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/net/tcp.h b/include/net/tcp.h
> >
> > index f8efe56bbccb..e1574e804530 100644
> >
> > --- a/include/net/tcp.h
> >
> > +++ b/include/net/tcp.h
> >
> > @@ -427,7 +427,8 @@ 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,
> >
> > - u32 *tw_isn);
> >
> > + u32 *tw_isn,
> >
> > + enum skb_drop_reason *drop_reason);
> >
> > struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
> >
> > struct request_sock *req, bool fastopen,
> >
> > bool *lost_race, enum skb_drop_reason *drop_reason);
> >
> > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> >
> > index 1cd0938d47e0..a9dde473a23f 100644
> >
> > --- a/net/ipv4/tcp_ipv4.c
> >
> > +++ b/net/ipv4/tcp_ipv4.c
> >
> > @@ -2417,7 +2417,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
> >
> > goto csum_error;
> >
> > }
> >
> > - tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn);
> >
> > + tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn, &drop_reason);
> >
> > switch (tw_status) {
> >
> > case TCP_TW_SYN: {
> >
> > struct sock *sk2 = inet_lookup_listener(net,
> >
> > diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
> >
> > index fb9349be36b8..d16dfd41397e 100644
> >
> > --- a/net/ipv4/tcp_minisocks.c
> >
> > +++ b/net/ipv4/tcp_minisocks.c
> >
> > @@ -97,7 +97,8 @@ static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq,
> >
> > */
> >
> > enum tcp_tw_status
> >
> > tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
> >
> > - const struct tcphdr *th, u32 *tw_isn)
> >
> > + const struct tcphdr *th, u32 *tw_isn,
> >
> > + enum skb_drop_reason *drop_reason)
> >
> > {
> >
> > struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
> >
> > u32 rcv_nxt = READ_ONCE(tcptw->tw_rcv_nxt);
> >
> > @@ -245,8 +246,10 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
> >
> > return TCP_TW_SYN;
> >
> > }
> >
> > - if (paws_reject)
> >
> > + if (paws_reject) {
> >
> > + *drop_reason = SKB_DROP_REASON_TCP_RFC7323_PAWS;
> >
> > __NET_INC_STATS(twsk_net(tw), LINUX_MIB_PAWSESTABREJECTED);
> >
>
> I think we should add a new SNMP value and drop reason for TW sockets.
>
> SNMP_MIB_ITEM("PAWSTimewait", LINUX_MIB_PAWSTIMEWAIT),
>
> and SKB_DROP_REASON_TCP_RFC7323_TW_PAWS ?
>
That makes sense, we've done similar things before, such as adding
PAWS_OLD_ACK previously.
Thanks for the suggestion!
--
pw-bot: cr