[maint,v2,2/2] batman-adv: invalidate checksum on fragment reassembly

Message ID 3f5713999a5f61ed7221944276393b4ff40a9416.1516701590.git.mschiffer@universe-factory.net (mailing list archive)
State Accepted, archived
Delegated to: Simon Wunderlich
Series [maint,v2,1/2] batman-adv: fix packet checksum in receive path |

Commit Message

Matthias Schiffer Jan. 23, 2018, 9:59 a.m. UTC
  A more sophisticated implementation could try to combine fragment checksums
when all fragments have CHECKSUM_COMPLETE and are split at even offsets.
For now, we just set ip_summed to CHECKSUM_NONE to avoid "hw csum failure"
warnings in the kernel log when fragmented frames are received. In
consequence, skb_pull_rcsum() can be replaced with skb_pull().

Note that in usual setups, packets don't reach batman-adv with
CHECKSUM_COMPLETE (I assume NICs bail out of checksumming when they see
batadv's ethtype?), which is why the log messages do nor occur on every
system using batman-adv. I could reproduce this issue by stacking
batman-adv on top of a VXLAN interface.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
 net/batman-adv/fragmentation.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)


diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
index ebe6e389..1bb2b43f 100644
--- a/net/batman-adv/fragmentation.c
+++ b/net/batman-adv/fragmentation.c
@@ -287,7 +287,8 @@  batadv_frag_merge_packets(struct hlist_head *chain)
 	/* Move the existing MAC header to just before the payload. (Override
 	 * the fragment header.)
-	skb_pull_rcsum(skb_out, hdr_size);
+	skb_pull(skb_out, hdr_size);
+	skb_out->ip_summed = CHECKSUM_NONE;
 	memmove(skb_out->data - ETH_HLEN, skb_mac_header(skb_out), ETH_HLEN);
 	skb_set_mac_header(skb_out, -ETH_HLEN);