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tcp: add TCP_OLD_SEQUENCE drop reason

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tcp_sequence() uses two conditions to decide to drop a packet,
and we currently report generic TCP_INVALID_SEQUENCE drop reason.

Duplicates are common, we need to distinguish them from
the other case.

I chose to not reuse TCP_OLD_DATA, and instead added
TCP_OLD_SEQUENCE drop reason.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230719064754.2794106-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Eric Dumazet 2023-07-19 06:47:54 +00:00 committed by Paolo Abeni
parent af1e2cffbd
commit b44693495a
2 changed files with 14 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/net/dropreason-core.h
View File

@ -30,6 +30,7 @@
FN(TCP_OVERWINDOW) \
FN(TCP_OFOMERGE) \
FN(TCP_RFC7323_PAWS) \
FN(TCP_OLD_SEQUENCE) \
FN(TCP_INVALID_SEQUENCE) \
FN(TCP_RESET) \
FN(TCP_INVALID_SYN) \
@ -188,6 +189,8 @@ enum skb_drop_reason {
* LINUX_MIB_PAWSESTABREJECTED
*/
SKB_DROP_REASON_TCP_RFC7323_PAWS,
/** @SKB_DROP_REASON_TCP_OLD_SEQUENCE: Old SEQ field (duplicate packet) */
SKB_DROP_REASON_TCP_OLD_SEQUENCE,
/** @SKB_DROP_REASON_TCP_INVALID_SEQUENCE: Not acceptable SEQ field */
SKB_DROP_REASON_TCP_INVALID_SEQUENCE,
/** @SKB_DROP_REASON_TCP_RESET: Invalid RST packet */

16
net/ipv4/tcp_input.c
View File

@ -4312,10 +4312,16 @@ static inline bool tcp_paws_discard(const struct sock *sk,
* (borrowed from freebsd)
*/
static inline bool tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq)
static enum skb_drop_reason tcp_sequence(const struct tcp_sock *tp,
u32 seq, u32 end_seq)
{
return !before(end_seq, tp->rcv_wup) &&
!after(seq, tp->rcv_nxt + tcp_receive_window(tp));
if (before(end_seq, tp->rcv_wup))
return SKB_DROP_REASON_TCP_OLD_SEQUENCE;
if (after(seq, tp->rcv_nxt + tcp_receive_window(tp)))
return SKB_DROP_REASON_TCP_INVALID_SEQUENCE;
return SKB_NOT_DROPPED_YET;
}
/* When we get a reset we do this. */
@ -5738,7 +5744,8 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
}
/* Step 1: check sequence number */
if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
reason = tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
if (reason) {
/* RFC793, page 37: "In all states except SYN-SENT, all reset
* (RST) segments are validated by checking their SEQ-fields."
* And page 69: "If an incoming segment is not acceptable,
@ -5755,7 +5762,6 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
} else if (tcp_reset_check(sk, skb)) {
goto reset;
}
SKB_DR_SET(reason, TCP_INVALID_SEQUENCE);
goto discard;
}