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tcp: add drop_reason support to tcp_disordered_ack()

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Following patch is adding a new drop_reason to tcp_validate_incoming().

Change tcp_disordered_ack() to not return a boolean anymore,
but a drop reason.

Change its name to tcp_disordered_ack_check()

Refactor tcp_validate_incoming() to ease the code
review of the following patch, and reduce indentation
level.

This patch is a refactor, with no functional change.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://patch.msgid.link/20250113135558.3180360-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2025-01-13 13:55:56 +00:00 committed by Jakub Kicinski
parent 652aac7ecd
commit ea98b61bdd
1 changed files with 43 additions and 34 deletions
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77
net/ipv4/tcp_input.c
View File

@ -4450,34 +4450,38 @@ static u32 tcp_tsval_replay(const struct sock *sk)
return inet_csk(sk)->icsk_rto * 1200 / HZ;
}
static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
static enum skb_drop_reason tcp_disordered_ack_check(const struct sock *sk,
const struct sk_buff *skb)
{
const struct tcp_sock *tp = tcp_sk(sk);
const struct tcphdr *th = tcp_hdr(skb);
u32 seq = TCP_SKB_CB(skb)->seq;
SKB_DR_INIT(reason, TCP_RFC7323_PAWS);
u32 ack = TCP_SKB_CB(skb)->ack_seq;
u32 seq = TCP_SKB_CB(skb)->seq;
return /* 1. Pure ACK with correct sequence number. */
(th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
/* 1. Is this not a pure ACK ? */
if (!th->ack || seq != TCP_SKB_CB(skb)->end_seq)
return reason;
/* 2. ... and duplicate ACK. */
ack == tp->snd_una &&
/* 2. Is its sequence not the expected one ? */
if (seq != tp->rcv_nxt)
return reason;
/* 3. ... and does not update window. */
!tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
/* 3. Is this not a duplicate ACK ? */
if (ack != tp->snd_una)
return reason;
/* 4. ... and sits in replay window. */
(s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <=
tcp_tsval_replay(sk);
}
/* 4. Is this updating the window ? */
if (tcp_may_update_window(tp, ack, seq, ntohs(th->window) <<
tp->rx_opt.snd_wscale))
return reason;
static inline bool tcp_paws_discard(const struct sock *sk,
const struct sk_buff *skb)
{
const struct tcp_sock *tp = tcp_sk(sk);
/* 5. Is this not in the replay window ? */
if ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) >
tcp_tsval_replay(sk))
return reason;
return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
!tcp_disordered_ack(sk, skb);
return 0;
}
/* Check segment sequence number for validity.
@ -5949,23 +5953,28 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
SKB_DR(reason);
/* RFC1323: H1. Apply PAWS check first. */
if (tcp_fast_parse_options(sock_net(sk), skb, th, tp) &&
tp->rx_opt.saw_tstamp &&
tcp_paws_discard(sk, skb)) {
if (!th->rst) {
if (unlikely(th->syn))
goto syn_challenge;
NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
if (!tcp_oow_rate_limited(sock_net(sk), skb,
LINUX_MIB_TCPACKSKIPPEDPAWS,
&tp->last_oow_ack_time))
tcp_send_dupack(sk, skb);
SKB_DR_SET(reason, TCP_RFC7323_PAWS);
goto discard;
}
/* Reset is accepted even if it did not pass PAWS. */
}
if (!tcp_fast_parse_options(sock_net(sk), skb, th, tp) ||
!tp->rx_opt.saw_tstamp ||
tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW))
goto step1;
reason = tcp_disordered_ack_check(sk, skb);
if (!reason)
goto step1;
/* Reset is accepted even if it did not pass PAWS. */
if (th->rst)
goto step1;
if (unlikely(th->syn))
goto syn_challenge;
NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
if (!tcp_oow_rate_limited(sock_net(sk), skb,
LINUX_MIB_TCPACKSKIPPEDPAWS,
&tp->last_oow_ack_time))
tcp_send_dupack(sk, skb);
goto discard;
step1:
/* Step 1: check sequence number */
reason = tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
if (reason) {