Olaf Dabrunz <Olaf.Dabrunz@gmx.de> writes:
>
> AFAICS from the kernel ChangeLogs Linux versions 2.4.* and 2.5.* do not
> implement the interoperability features described above. Is that correct?
> Is someone working on a patch that implements these features?
Olaf:
Here's a small patch I put together a while ago and have been using
with some success. It implements *only* the SYN retransmission in the
"no reply" case (after a user-configurable number of lost SYN packets)
but won't help with the RST case.
It adds a new sysctl variable "tcp_ecn_retries". The default value of
zero gives the old behaviour. But, for example:
echo 3 >/proc/sys/net/ipv4/tcp_ecn_retries
will retry with an ECN-disabled SYN after three unanswered ECN-enabled
SYNs (i.e., after a 20 second delay or so). Of course, it doesn't
keep track of what hosts need this kluge. Every new TCP connection to
a naughty host will be negotiated the same way with a long initial
delay.
The following patch is against 2.4.19-pre10-ac2. I imagine it'll
apply cleanly to more recent kernels except for the index in
"sysctl.h".
I have my doubts about it (in other words, I really don't understand
enough about the network code to do it right), but after I got it
working for myself, I kind of lost interest.
Anyway, hope this helps.
Kevin Buhr <buhr@telus.net>
* * *
diff -ru linux-2.4.19-pre10-ac2/include/linux/sysctl.h linux-2.4.19-pre10-ac2-local/include/linux/sysctl.h
--- linux-2.4.19-pre10-ac2/include/linux/sysctl.h Thu Jun 6 15:16:50 2002
+++ linux-2.4.19-pre10-ac2-local/include/linux/sysctl.h Thu Jun 6 15:51:07 2002
@@ -298,7 +298,8 @@
NET_IPV4_NONLOCAL_BIND=88,
NET_IPV4_ICMP_RATELIMIT=89,
NET_IPV4_ICMP_RATEMASK=90,
- NET_TCP_TW_REUSE=91
+ NET_TCP_TW_REUSE=91,
+ NET_IPV4_TCP_ECN_RETRIES=92,
};
enum {
diff -ru linux-2.4.19-pre10-ac2/include/net/tcp.h linux-2.4.19-pre10-ac2-local/include/net/tcp.h
--- linux-2.4.19-pre10-ac2/include/net/tcp.h Thu Jun 6 15:16:02 2002
+++ linux-2.4.19-pre10-ac2-local/include/net/tcp.h Thu Jun 6 15:51:08 2002
@@ -454,6 +454,7 @@
extern int sysctl_tcp_fack;
extern int sysctl_tcp_reordering;
extern int sysctl_tcp_ecn;
+extern int sysctl_tcp_ecn_retries;
extern int sysctl_tcp_dsack;
extern int sysctl_tcp_mem[3];
extern int sysctl_tcp_wmem[3];
diff -ru linux-2.4.19-pre10-ac2/include/net/tcp_ecn.h linux-2.4.19-pre10-ac2-local/include/net/tcp_ecn.h
--- linux-2.4.19-pre10-ac2/include/net/tcp_ecn.h Fri Nov 2 17:43:26 2001
+++ linux-2.4.19-pre10-ac2-local/include/net/tcp_ecn.h Thu Jun 6 15:42:48 2002
@@ -38,6 +38,12 @@
}
static __inline__ void
+TCP_ECN_noecn_syn(struct sk_buff *skb)
+{
+ TCP_SKB_CB(skb)->flags &= ~(TCPCB_FLAG_ECE|TCPCB_FLAG_CWR);
+}
+
+static __inline__ void
TCP_ECN_make_synack(struct open_request *req, struct tcphdr *th)
{
if (req->ecn_ok)
diff -ru linux-2.4.19-pre10-ac2/net/ipv4/sysctl_net_ipv4.c linux-2.4.19-pre10-ac2-local/net/ipv4/sysctl_net_ipv4.c
--- linux-2.4.19-pre10-ac2/net/ipv4/sysctl_net_ipv4.c Thu Jun 6 15:16:03 2002
+++ linux-2.4.19-pre10-ac2-local/net/ipv4/sysctl_net_ipv4.c Thu Jun 6 15:42:48 2002
@@ -203,6 +203,8 @@
&sysctl_tcp_reordering, sizeof(int), 0644, NULL, &proc_dointvec},
{NET_TCP_ECN, "tcp_ecn",
&sysctl_tcp_ecn, sizeof(int), 0644, NULL, &proc_dointvec},
+ {NET_IPV4_TCP_ECN_RETRIES, "tcp_ecn_retries",
+ &sysctl_tcp_ecn_retries, sizeof(int), 0644, NULL, &proc_dointvec},
{NET_TCP_DSACK, "tcp_dsack",
&sysctl_tcp_dsack, sizeof(int), 0644, NULL, &proc_dointvec},
{NET_TCP_MEM, "tcp_mem",
diff -ru linux-2.4.19-pre10-ac2/net/ipv4/tcp_timer.c linux-2.4.19-pre10-ac2-local/net/ipv4/tcp_timer.c
--- linux-2.4.19-pre10-ac2/net/ipv4/tcp_timer.c Mon Oct 1 09:19:57 2001
+++ linux-2.4.19-pre10-ac2-local/net/ipv4/tcp_timer.c Tue Aug 13 10:43:07 2002
@@ -30,6 +30,7 @@
int sysctl_tcp_retries1 = TCP_RETR1;
int sysctl_tcp_retries2 = TCP_RETR2;
int sysctl_tcp_orphan_retries;
+int sysctl_tcp_ecn_retries;
static void tcp_write_timer(unsigned long);
static void tcp_delack_timer(unsigned long);
@@ -373,6 +374,11 @@
}
tcp_enter_loss(sk, 0);
+
+ /* If this is a SYN packet, retry with ECN disabled */
+ if (sk->state == TCP_SYN_SENT
+ && sysctl_tcp_ecn_retries && tp->retransmits+1 >= sysctl_tcp_ecn_retries)
+ TCP_ECN_noecn_syn(skb_peek(&sk->write_queue));
if (tcp_retransmit_skb(sk, skb_peek(&sk->write_queue)) > 0) {
/* Retransmission failed because of local congestion,
-
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This archive was generated by hypermail 2b29 : Thu Aug 15 2002 - 22:00:33 EST