RHEL7 kernel backported 5a21232983aa ("net: Support for csum_bad in skbuff")
That's a broken commit because skb_clone() leaves ->csum_bad field
uninitialized. Later this leads to checksum failures
(e.g. tcp_v4_rcv() -> skb_checksum_init()) and loosing packets.
The upstream kernel is not affected by this, because the bug was silently
fixed up by b19372273164 ("net: reorganize sk_buff for faster
__copy_skb_header()")
in the same kernel version.
We don't want to backport b19372273164 because it changes KABI and we would
like to avoid that. Instead, lets directly copy ->csum_bad along with
->csum_level and ->remcsum_offload fields which are also copied in the
upstream kernel after b19372273164 commit.
Note that we already have stepped on this in
https://jira.sw.ru/browse/PSBM-38924
but this wasn't properly fixed at the time.
https://jira.sw.ru/browse/PSBM-47290
Signed-off-by: Andrey Ryabinin <[email protected]>
---
net/core/skbuff.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 686ae59..7334046 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -817,6 +817,9 @@ static void __copy_skb_header(struct sk_buff *new, const
struct sk_buff *old)
new->encap_hdr_csum = old->encap_hdr_csum;
new->csum_valid = old->csum_valid;
new->csum_complete_sw = old->csum_complete_sw;
+ new->csum_bad = old->csum_bad;
+ new->csum_level = old->csum_level;
+ new->remcsum_offload = old->remcsum_offload;
#ifdef CONFIG_XFRM
new->sp = secpath_get(old->sp);
#endif
--
2.7.3
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