[3284] in linux-net channel archive
Fix check
daemon@ATHENA.MIT.EDU (Alan Cox)
Tue Jun 18 08:01:52 1996
Date: Mon, 17 Jun 96 21:54 BST
From: alan@lxorguk.ukuu.org.uk (Alan Cox)
To: linux-net@vger.rutgers.edu, schenk@rnode84.cs.toronto.edu
Can people seeing the TCP: **bug**: copy <=0 message try this fix
--- net/ipv4/tcp.c~ Mon Jun 17 22:48:06 1996
+++ net/ipv4/tcp.c Mon Jun 17 22:52:46 1996
@@ -950,40 +950,44 @@
return -EPIPE;
}
- /*
- * The following code can result in copy <= if sk->mss is ever
- * decreased. It shouldn't be. sk->mss is min(sk->mtu, sk->max_window).
- * sk->mtu is constant once SYN processing is finished. I.e. we
- * had better not get here until we've seen his SYN and at least one
- * valid ack. (The SYN sets sk->mtu and the ack sets sk->max_window.)
- * But ESTABLISHED should guarantee that. sk->max_window is by definition
- * non-decreasing. Note that any ioctl to set user_mss must be done
- * before the exchange of SYN's. If the initial ack from the other
- * end has a window of 0, max_window and thus mss will both be 0.
- */
+ /*
+ * The following code can result in copy <= if sk->mss is ever
+ * decreased. It shouldn't be. sk->mss is min(sk->mtu, sk->max_window).
+ * sk->mtu is constant once SYN processing is finished. I.e. we
+ * had better not get here until we've seen his SYN and at least one
+ * valid ack. (The SYN sets sk->mtu and the ack sets sk->max_window.)
+ * But ESTABLISHED should guarantee that. sk->max_window is by definition
+ * non-decreasing. Note that any ioctl to set user_mss must be done
+ * before the exchange of SYN's. If the initial ack from the other
+ * end has a window of 0, max_window and thus mss will both be 0.
+ */
- /*
- * Now we need to check if we have a half built packet.
- */
+ /*
+ * Now we need to check if we have a half built packet.
+ */
#ifndef CONFIG_NO_PATH_MTU_DISCOVERY
- /*
- * FIXME: I'm almost sure that this fragment is BUG,
- * but it works... I do not know why 8) --ANK
- *
- * Really, we should rebuild all the queues...
- * It's difficult. Temporary hack is to send all
- * queued segments with allowed fragmentation.
- */
- {
- int new_mss = min(sk->mtu, sk->max_window);
- if (new_mss < sk->mss)
+ /*
+ * FIXME: I'm almost sure that this fragment is BUG,
+ * but it works... I do not know why 8) --ANK
+ *
+ * Really, we should rebuild all the queues...
+ * It's difficult. Temporary hack is to send all
+ * queued segments with allowed fragmentation.
+ */
{
- tcp_send_partial(sk);
- sk->mss = new_mss;
+ int new_mss = min(sk->mtu, sk->max_window);
+ if (new_mss < sk->mss)
+ {
+ tcp_send_partial(sk);
+ sk->mss = new_mss;
+ }
}
- }
#endif
+ /*
+ * If there is a partly filled frame we can fill
+ * out.
+ */
if ((skb = tcp_dequeue_partial(sk)) != NULL)
{
int tcp_size;
@@ -994,11 +998,33 @@
if (!(flags & MSG_OOB))
{
copy = min(sk->mss - tcp_size, seglen);
+
+ /*
+ * Now we may find the frame is as big, or too
+ * big for our MSS. Thats all fine. It means the
+ * MSS shrank (from an ICMP) after we allocated
+ * this frame.
+ */
+
if (copy <= 0)
{
- printk(KERN_CRIT "TCP: **bug**: \"copy\" <= 0\n");
- return -EFAULT;
+ /*
+ * Send the now forced complete frame out.
+ *
+ * Note for 2.1: The MSS reduce code ought to
+ * flush any frames in partial that are now
+ * full sized. Not serious, potential tiny
+ * performance hit.
+ */
+ tcp_send_skb(sk,skb);
+ /*
+ * Get a new buffer and try again.
+ */
+ continue;
}
+ /*
+ * Otherwise continue to fill the buffer.
+ */
tcp_size += copy;
memcpy_fromfs(skb_put(skb,copy), from, copy);
skb->csum = csum_partial(skb->tail - tcp_size, tcp_size, 0);
