netdev - Re: [PATCH] make _minimum_ TCP retransmission timeout configurable take 2

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20070830.220911.41008322.davem@davemloft.net>
Date:	Thu, 30 Aug 2007 22:09:11 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	rick.jones2@...com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] make _minimum_ TCP retransmission timeout configurable
 take 2

From: Rick Jones <rick.jones2@...com>
Date: Thu, 30 Aug 2007 18:07:13 -0700

> Anyhow, I'll try grubbing around the source code (already doing that to 
> see about writing a pet tcp cong module) but if pointers to the likely 
> relevant files were available I could try to help thrash-out the routing 
> metric version.  Like I said the consumers of this are a triffle well, 
> "anxious" :)

The change is actually a lot simpler than the sysctl version.

In fact it borders on trivial :-)

Signed-off-by: David S. Miller <davem@...emloft.net>

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index c91476c..dff3192 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -351,6 +351,8 @@ enum
 #define RTAX_INITCWND RTAX_INITCWND
 	RTAX_FEATURES,
 #define RTAX_FEATURES RTAX_FEATURES
+	RTAX_RTO_MIN,
+#define RTAX_RTO_MIN RTAX_RTO_MIN
 	__RTAX_MAX
 };
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9785df3..1ee7212 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -555,6 +555,16 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
 		tcp_grow_window(sk, skb);
 }
 
+static u32 tcp_rto_min(struct sock *sk)
+{
+	struct dst_entry *dst = __sk_dst_get(sk);
+	u32 rto_min = TCP_RTO_MIN;
+
+	if (dst_metric_locked(dst, RTAX_RTO_MIN))
+		rto_min = dst->metrics[RTAX_RTO_MIN-1];
+	return rto_min;
+}
+
 /* Called to compute a smoothed rtt estimate. The data fed to this
  * routine either comes from timestamps, or from segments that were
  * known _not_ to have been retransmitted [see Karn/Partridge
@@ -616,13 +626,13 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
 			if (tp->mdev_max < tp->rttvar)
 				tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
 			tp->rtt_seq = tp->snd_nxt;
-			tp->mdev_max = TCP_RTO_MIN;
+			tp->mdev_max = tcp_rto_min(sk);
 		}
 	} else {
 		/* no previous measure. */
 		tp->srtt = m<<3;	/* take the measured time to be rtt */
 		tp->mdev = m<<1;	/* make sure rto = 3*rtt */
-		tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
+		tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
 		tp->rtt_seq = tp->snd_nxt;
 	}
 }


-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html