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authorPengcheng Yang <yangpc@wangsu.com>2019-12-30 17:54:41 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-01-12 12:21:48 +0100
commit68fe2b265a674fe479f09762a1c6ffa74e25cd43 (patch)
tree89234628097765f2a55ee3ffad752ebdc8efd64d
parent50027f1c78abced651d03e2a0d88b7caa2b9a0c2 (diff)
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tcp: fix "old stuff" D-SACK causing SACK to be treated as D-SACK
[ Upstream commit c9655008e7845bcfdaac10a1ed8554ec167aea88 ] When we receive a D-SACK, where the sequence number satisfies: undo_marker <= start_seq < end_seq <= prior_snd_una we consider this is a valid D-SACK and tcp_is_sackblock_valid() returns true, then this D-SACK is discarded as "old stuff", but the variable first_sack_index is not marked as negative in tcp_sacktag_write_queue(). If this D-SACK also carries a SACK that needs to be processed (for example, the previous SACK segment was lost), this SACK will be treated as a D-SACK in the following processing of tcp_sacktag_write_queue(), which will eventually lead to incorrect updates of undo_retrans and reordering. Fixes: fd6dad616d4f ("[TCP]: Earlier SACK block verification & simplify access to them") Signed-off-by: Pengcheng Yang <yangpc@wangsu.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--net/ipv4/tcp_input.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a2e52ad7cdab..67e44e6717b0 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1727,8 +1727,11 @@ tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
}
/* Ignore very old stuff early */
- if (!after(sp[used_sacks].end_seq, prior_snd_una))
+ if (!after(sp[used_sacks].end_seq, prior_snd_una)) {
+ if (i == 0)
+ first_sack_index = -1;
continue;
+ }
used_sacks++;
}