Commit b4469349 authored by Eric Dumazet's avatar Eric Dumazet Committed by Paolo Abeni
Browse files

tcp: add TCP_OLD_SEQUENCE drop reason 



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: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230719064754.2794106-1-edumazet@google.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent af1e2cff

include/net/dropreason-core.h

+3 −0
Original line number Diff line number Diff line
@@ -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 */

net/ipv4/tcp_input.c

+11 −5
Original line number Diff line number Diff line
@@ -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;

	}