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TCP state handling reparses the skb to find the TCP header. For IPv6 it
uses sizeof(struct ipv6hdr), while the surrounding IPVS code already
parsed the packet with ip_vs_fill_iph_skb() and has the real
transport-header offset in iph.len.
This makes TCP state handling look at the wrong bytes when an IPv6
packet carries extension headers. Use the parsed transport offset passed
down from ip_vs_set_state() when reading the TCP header.
For IPv4 and for IPv6 packets without extension headers, the passed
offset matches the previous value.
Fixes: 0bbdd42b7efa6 ("IPVS: Extend protocol DNAT/SNAT and state handlers")
Link:
https://lore.kernel.org/netdev/20260705125659.37744-1-zhaoyz24@xxxxxxxxxxxxxxxxxxxxx/
Reported-by: Yizhou Zhao <zhaoyz24@xxxxxxxxxxxxxxxxxxxxx>
Reported-by: Yuxiang Yang <yangyx22@xxxxxxxxxxxxxxxxxxxxx>
Reported-by: Ao Wang <wangao@xxxxxxxxxx>
Reported-by: Xuewei Feng <fengxw06@xxxxxxx>
Reported-by: Qi Li <qli01@xxxxxxxxxxxxxxx>
Reported-by: Ke Xu <xuke@xxxxxxxxxxxxxxx>
Assisted-by: Claude Code:GLM-5.2
Signed-off-by: Yizhou Zhao <zhaoyz24@xxxxxxxxxxxxxxxxxxxxx>
---
net/netfilter/ipvs/ip_vs_proto_tcp.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/net/netfilter/ipvs/ip_vs_proto_tcp.c
b/net/netfilter/ipvs/ip_vs_proto_tcp.c
index 2d3f6aeafe52..f86b763efcc4 100644
--- a/net/netfilter/ipvs/ip_vs_proto_tcp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c
@@ -584,13 +584,7 @@ tcp_state_transition(struct ip_vs_conn *cp, int direction,
{
struct tcphdr _tcph, *th;
-#ifdef CONFIG_IP_VS_IPV6
- int ihl = cp->af == AF_INET ? ip_hdrlen(skb) : sizeof(struct ipv6hdr);
-#else
- int ihl = ip_hdrlen(skb);
-#endif
-
- th = skb_header_pointer(skb, ihl, sizeof(_tcph), &_tcph);
+ th = skb_header_pointer(skb, iph_len, sizeof(_tcph), &_tcph);
if (th == NULL)
return;
--
2.34.1
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