>Could the problem be that the e100 can do IP receive checksumming on
>the board,
>but the eepro driver doesn't enable it. When the board is doing checksum
>offload, then the csum field isn't set.
>
>Please try disabling receive checksumming on the e100 driver
>
> modprobe e100 XsumRX=0
>
>If this is the problem, it exists both 2.4 and 2.6.
Indeed: with XsumRX=0,0 the BUG doesn't happen. I put some debugging
code in dev.c:
=== CUT HERE ===
--- dev.c.orig 2003-08-28 20:00:22.000000000 +0200
+++ dev.c 2003-08-28 20:59:19.000000000 +0200
@@ -987,9 +987,29 @@
offset = skb->tail - skb->h.raw;
if (offset <= 0)
BUG();
- if (skb->csum+2 > offset)
+/* if (skb->csum+2 > offset)
BUG();
-
+*/
+ if (skb->csum+2 > offset) {
+ printk (KERN_EMERG "skb->csum+2=%d, offset=%d,
skb->ip_summed=%d\n", skb->csum+2, offset, (int)(skb->ip_summed));
+ printk (KERN_EMERG
"skb->mac.ethernet->h_dest=%0.2x:%0.2x:%0.2x:%0.2x:%0.2x:%0.2x\n",
+ (unsigned int)(skb->mac.ethernet->h_dest [0]),
+ (unsigned int)(skb->mac.ethernet->h_dest [1]),
+ (unsigned int)(skb->mac.ethernet->h_dest [2]),
+ (unsigned int)(skb->mac.ethernet->h_dest [3]),
+ (unsigned int)(skb->mac.ethernet->h_dest [4]),
+ (unsigned int)(skb->mac.ethernet->h_dest [5])
+ );
+ printk (KERN_EMERG
"skb->mac.ethernet->h_source=%0.2x:%0.2x:%0.2x:%0.2x:%0.2x:%0.2x\n",
+ (unsigned
int)(skb->mac.ethernet->h_source [0]),
+ (unsigned
int)(skb->mac.ethernet->h_source [1]),
+ (unsigned
int)(skb->mac.ethernet->h_source [2]),
+ (unsigned
int)(skb->mac.ethernet->h_source [3]),
+ (unsigned
int)(skb->mac.ethernet->h_source [4]),
+ (unsigned int)(skb->mac.ethernet->h_source [5])
+ );
+ BUG ();
+ }
*(u16*)(skb->h.raw + skb->csum) = csum_fold(csum);
skb->ip_summed = CHECKSUM_NONE;
return skb;
=== CUT HERE ===
It says (just before the BUG):
skb->csum+2=33323, offset=168, skb->ip_summed=1
skb->mac.ethernet->h_dest=ff:ff:ff:ff:ff:ff
skb->mac.ethernet->h_source=00:d0:b7:3c:78:0a
I also put a few lines in e100_main.c:
=== CUT HERE ===
--- e100_main.c.orig 2003-08-28 21:01:07.000000000 +0200
+++ e100_main.c 2003-08-28 21:07:10.000000000 +0200
@@ -2051,11 +2051,14 @@
if (bdp->flags & DF_CSUM_OFFLOAD) {
if (bdp->rev_id >= D102_REV_ID) {
skb->ip_summed = e100_D102_check_checksum(rfd);
+ printk (KERN_ERR "e100_D102:
skb->csum+2=%d,offset=%d, skb->ip_summed=%d\n", skb->csum+2,
skb->tail - skb->h.raw, (int)(skb->ip_summed));
} else {
skb->ip_summed = e100_D101M_checksum(bdp, skb);
+ printk (KERN_ERR "e100_D101M:
skb->csum+2=%d,offset=%d, skb->ip_summed=%d\n", skb->csum+2,
skb->tail - skb->h.raw, (int)(skb->ip_summed));
}
} else {
skb->ip_summed = CHECKSUM_NONE;
+ printk (KERN_ERR "e100_NOOFF:
skb->csum+2=%d,offset=%d, skb->ip_summed=%d\n", skb->csum+2,
skb->tail - skb->h.raw, (int)(skb->ip_summed));
}
bdp->drv_stats.net_stats.rx_bytes += skb->len;
=== CUT HERE ===
and my console was flooded with these:
e100_D101M: skb->csum+2=47564,offset=-2789414, skb->ip_summed=1
e100_D101M: skb->csum+2=38865,offset=3991018, skb->ip_summed=0
e100_D101M: skb->csum+2=33998,offset=4009612, skb->ip_summed=1
e100_D101M: skb->csum+2=11471,offset=845290, skb->ip_summed=1
e100_D101M: skb->csum+2=33323,offset=4036692, skb->ip_summed=1
^^^^^
this line was printed just above the BUG. The bug itself is
essentially the same as before; just different offsets.
I think the packet in question is a broadcast of linux-ha sent out by
a completely unrelated machine that happens to be on the same network:
uml:/usr/src/linux/drivers/net/e100# tcpdump -i br0 -e -n -q ether
host 00:d0:b7:3c:78:0a
tcpdump: listening on br0
22:11:40.413171 0:d0:b7:3c:78:a ff:ff:ff:ff:ff:ff 182:
10.96.96.25.1025 > 10.96.96.255.694: udp 140
22:11:42.413154 0:d0:b7:3c:78:a ff:ff:ff:ff:ff:ff 182:
10.96.96.25.1025 > 10.96.96.255.694: udp 140
[and so on; the machine is idle at that time of the day]
Q: the 'offset' looks wrong in my code in e100_main.c [I didn't
further investigate this]; but the skb->csum shows strong
coincidence. What is happening here ?
Thanks in advance
Hannes
