We need to update the skb->csum after pulling the skb, otherwise
checksum validation will fail. This fixes multicast packet loss for
bridges and splats like the following:
[...]
[ 43.986968] eth0: hw csum failure
[ 43.990344] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.4.0 #2
[ 43.996193] Hardware name: BCM2709
[ 43.999647] [<800204e0>] (unwind_backtrace) from [<8001cf14>]
(show_stack+0x10/0x14)
[ 44.007432] [<8001cf14>] (show_stack) from [<801ab614>]
(dump_stack+0x80/0x90)
[ 44.014695] [<801ab614>] (dump_stack) from [<802e4548>]
(__skb_checksum_complete+0x6c/0xac)
[ 44.023090] [<802e4548>] (__skb_checksum_complete) from [<803a055c>]
(ipv6_mc_validate_checksum+0x104/0x178)
[ 44.032959] [<803a055c>] (ipv6_mc_validate_checksum) from [<802e111c>]
(skb_checksum_trimmed+0x130/0x188)
[ 44.042565] [<802e111c>] (skb_checksum_trimmed) from [<803a06e8>]
(ipv6_mc_check_mld+0x118/0x338)
[ 44.051501] [<803a06e8>] (ipv6_mc_check_mld) from [<803b2c98>]
(br_multicast_rcv+0x5dc/0xd00)
[ 44.060077] [<803b2c98>] (br_multicast_rcv) from [<803aa510>]
(br_handle_frame_finish+0xac/0x51c)
[...]
Fixes: 9afd85c9e455 ("net: Export IGMP/MLD message validation code")
Reported-by: Álvaro Fernández Rojas <nolt...@gmail.com>
Signed-off-by: Linus Lüssing <linus.luess...@c0d3.blue>
---
Steinar, can you check whether this fixes the bridge issues you reported on
bugzilla #99081? Not quite sure whether it is the same as yours as you
do not seem to have any such call traces.
I am not super happy with how this patch looks, but there is no "skb_push_rcsum"
available and skb_pull_rcsum() seems non-reversible as is. Alternative
suggestions
always welcome.
net/core/skbuff.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 5bf88f5..6c34ef6 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4076,6 +4076,11 @@ struct sk_buff *skb_checksum_trimmed(struct sk_buff *skb,
struct sk_buff *skb_chk;
unsigned int offset = skb_transport_offset(skb);
__sum16 ret;
+ int ip_summed;
+ int csum_valid;
+ int csum_level;
+ int csum_bad;
+ __wsum csum;
skb_chk = skb_checksum_maybe_trim(skb, transport_len);
if (!skb_chk)
@@ -4084,10 +4089,22 @@ struct sk_buff *skb_checksum_trimmed(struct sk_buff
*skb,
if (!pskb_may_pull(skb_chk, offset))
goto err;
- __skb_pull(skb_chk, offset);
+ ip_summed = skb->ip_summed;
+ csum_valid = skb->csum_valid;
+ csum_level = skb->csum_level;
+ csum_bad = skb->csum_bad;
+ csum = skb->csum;
+
+ skb_pull_rcsum(skb_chk, offset);
ret = skb_chkf(skb_chk);
__skb_push(skb_chk, offset);
+ skb->ip_summed = ip_summed;
+ skb->csum_valid = csum_valid;
+ skb->csum_level = csum_level;
+ skb->csum_bad = csum_bad;
+ skb->csum = csum;
+
if (ret)
goto err;
--
1.7.10.4
