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SubjectRe: 2.4.4: Kernel crash, possibly tcp related
Date
Hello!

> this is the strict fix:

Andrea, you caught the problem!

The fix is not right though (it is equivalent to straight
tp->send_head=NULL, as you noticed. It also corrupts queue in
an opposite manner.) Right fix is appended.

Explanation: in do_fault we must undo effect of enqueueing new segment
in the case the segment remained empty. tp->send_head points to
the first unsent skb in queue and it is NULL when and only when
all the skbs are already sent. (Invariant is: tp->send_head==NULL ||
tp->send_head->seq == tp->snd_nxt)
I crapped this case except for the case when queue is completely empty,
so that the last sent skb was accounted in packets_out twice...

Damn, what a silly mistake was it... shame.

Alexey


--- ../vger3-010426/linux/net/ipv4/tcp.c Wed Apr 25 21:02:18 2001
+++ linux/net/ipv4/tcp.c Tue May 1 20:38:44 2001
@@ -1185,7 +1187,7 @@
if (skb->len==0) {
if (tp->send_head == skb) {
tp->send_head = skb->prev;
- if (tp->send_head == (struct sk_buff*)&sk->write_queue)
+ if (TCP_SKB_CB(skb)->seq == tp->snd_nxt)
tp->send_head = NULL;
}
__skb_unlink(skb, skb->list);
-
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