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Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c32
1 files changed, 25 insertions, 7 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 20f89078fa8d..c15ca207dd85 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -948,21 +948,34 @@ struct tcp_sacktag_state {
struct rate_sample *rate;
};
-/* Take a notice that peer is sending D-SACKs */
+/* Take a notice that peer is sending D-SACKs. Skip update of data delivery
+ * and spurious retransmission information if this DSACK is unlikely caused by
+ * sender's action:
+ * - DSACKed sequence range is larger than maximum receiver's window.
+ * - Total no. of DSACKed segments exceed the total no. of retransmitted segs.
+ */
static u32 tcp_dsack_seen(struct tcp_sock *tp, u32 start_seq,
u32 end_seq, struct tcp_sacktag_state *state)
{
u32 seq_len, dup_segs = 1;
- if (before(start_seq, end_seq)) {
- seq_len = end_seq - start_seq;
- if (seq_len > tp->mss_cache)
- dup_segs = DIV_ROUND_UP(seq_len, tp->mss_cache);
- }
+ if (!before(start_seq, end_seq))
+ return 0;
+
+ seq_len = end_seq - start_seq;
+ /* Dubious DSACK: DSACKed range greater than maximum advertised rwnd */
+ if (seq_len > tp->max_window)
+ return 0;
+ if (seq_len > tp->mss_cache)
+ dup_segs = DIV_ROUND_UP(seq_len, tp->mss_cache);
+
+ tp->dsack_dups += dup_segs;
+ /* Skip the DSACK if dup segs weren't retransmitted by sender */
+ if (tp->dsack_dups > tp->total_retrans)
+ return 0;
tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
tp->rack.dsack_seen = 1;
- tp->dsack_dups += dup_segs;
state->flag |= FLAG_DSACKING_ACK;
/* A spurious retransmission is delivered */
@@ -1215,6 +1228,11 @@ static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
}
dup_segs = tcp_dsack_seen(tp, start_seq_0, end_seq_0, state);
+ if (!dup_segs) { /* Skip dubious DSACK */
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKIGNOREDDUBIOUS);
+ return false;
+ }
+
NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPDSACKRECVSEGS, dup_segs);
/* D-SACK for already forgotten data... Do dumb counting. */