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authorDamian Lukowski <damian@tvk.rwth-aachen.de>2009-08-26 00:16:31 +0000
committerDavid S. Miller <davem@davemloft.net>2009-09-01 02:45:42 -0700
commitf1ecd5d9e7366609d640ff4040304ea197fbc618 (patch)
treeef4901d52ad0d2555094998f02d08788e197c20a /net/ipv4/tcp_ipv4.c
parent4d1a2d9ec1c17df077ed09a0d135bccf5637a3b7 (diff)
Revert Backoff [v3]: Revert RTO on ICMP destination unreachable
Here, an ICMP host/network unreachable message, whose payload fits to TCP's SND.UNA, is taken as an indication that the RTO retransmission has not been lost due to congestion, but because of a route failure somewhere along the path. With true congestion, a router won't trigger such a message and the patched TCP will operate as standard TCP. This patch reverts one RTO backoff, if an ICMP host/network unreachable message, whose payload fits to TCP's SND.UNA, arrives. Based on the new RTO, the retransmission timer is reset to reflect the remaining time, or - if the revert clocked out the timer - a retransmission is sent out immediately. Backoffs are only reverted, if TCP is in RTO loss recovery, i.e. if there have been retransmissions and reversible backoffs, already. Changes from v2: 1) Renaming of skb in tcp_v4_err() moved to another patch. 2) Reintroduced tcp_bound_rto() and __tcp_set_rto(). 3) Fixed code comments. Signed-off-by: Damian Lukowski <damian@tvk.rwth-aachen.de> Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_ipv4.c')
-rw-r--r--net/ipv4/tcp_ipv4.c37
1 files changed, 37 insertions, 0 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 6ca1bc8c302..6755e29a6dd 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -332,12 +332,15 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
{
struct iphdr *iph = (struct iphdr *)icmp_skb->data;
struct tcphdr *th = (struct tcphdr *)(icmp_skb->data + (iph->ihl << 2));
+ struct inet_connection_sock *icsk;
struct tcp_sock *tp;
struct inet_sock *inet;
const int type = icmp_hdr(icmp_skb)->type;
const int code = icmp_hdr(icmp_skb)->code;
struct sock *sk;
+ struct sk_buff *skb;
__u32 seq;
+ __u32 remaining;
int err;
struct net *net = dev_net(icmp_skb->dev);
@@ -367,6 +370,7 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
if (sk->sk_state == TCP_CLOSE)
goto out;
+ icsk = inet_csk(sk);
tp = tcp_sk(sk);
seq = ntohl(th->seq);
if (sk->sk_state != TCP_LISTEN &&
@@ -393,6 +397,39 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
}
err = icmp_err_convert[code].errno;
+ /* check if icmp_skb allows revert of backoff
+ * (see draft-zimmermann-tcp-lcd) */
+ if (code != ICMP_NET_UNREACH && code != ICMP_HOST_UNREACH)
+ break;
+ if (seq != tp->snd_una || !icsk->icsk_retransmits ||
+ !icsk->icsk_backoff)
+ break;
+
+ icsk->icsk_backoff--;
+ inet_csk(sk)->icsk_rto = __tcp_set_rto(tp) <<
+ icsk->icsk_backoff;
+ tcp_bound_rto(sk);
+
+ skb = tcp_write_queue_head(sk);
+ BUG_ON(!skb);
+
+ remaining = icsk->icsk_rto - min(icsk->icsk_rto,
+ tcp_time_stamp - TCP_SKB_CB(skb)->when);
+
+ if (remaining) {
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+ remaining, TCP_RTO_MAX);
+ } else if (sock_owned_by_user(sk)) {
+ /* RTO revert clocked out retransmission,
+ * but socket is locked. Will defer. */
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+ HZ/20, TCP_RTO_MAX);
+ } else {
+ /* RTO revert clocked out retransmission.
+ * Will retransmit now */
+ tcp_retransmit_timer(sk);
+ }
+
break;
case ICMP_TIME_EXCEEDED:
err = EHOSTUNREACH;