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authorEric Dumazet <edumazet@google.com>2015-03-16 21:06:20 -0700
committerDavid S. Miller <davem@davemloft.net>2015-03-17 15:18:00 -0400
commit7970ddc8f9ffe149b392975da60739ccd1796dea (patch)
tree9c5c365b44d7e6f4e7701d8235402b914ce25b79 /net/ipv4
parent1bfc4438a7ef99e8a6cba0bd3a86249430256621 (diff)
tcp: uninline tcp_oow_rate_limited()
tcp_oow_rate_limited() is hardly used in fast path, there is no point inlining it. Signed-of-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/tcp_input.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 10d6bd93f229..7257eb206c07 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3321,6 +3321,36 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32
return flag;
}
+/* Return true if we're currently rate-limiting out-of-window ACKs and
+ * thus shouldn't send a dupack right now. We rate-limit dupacks in
+ * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
+ * attacks that send repeated SYNs or ACKs for the same connection. To
+ * do this, we do not send a duplicate SYNACK or ACK if the remote
+ * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
+ */
+bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
+ int mib_idx, u32 *last_oow_ack_time)
+{
+ /* Data packets without SYNs are not likely part of an ACK loop. */
+ if ((TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) &&
+ !tcp_hdr(skb)->syn)
+ goto not_rate_limited;
+
+ if (*last_oow_ack_time) {
+ s32 elapsed = (s32)(tcp_time_stamp - *last_oow_ack_time);
+
+ if (0 <= elapsed && elapsed < sysctl_tcp_invalid_ratelimit) {
+ NET_INC_STATS_BH(net, mib_idx);
+ return true; /* rate-limited: don't send yet! */
+ }
+ }
+
+ *last_oow_ack_time = tcp_time_stamp;
+
+not_rate_limited:
+ return false; /* not rate-limited: go ahead, send dupack now! */
+}
+
/* RFC 5961 7 [ACK Throttling] */
static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
{