--- /dev/null
+From 05cfe9863ef049d98141dc2969eefde72fb07625 Mon Sep 17 00:00:00 2001
+From: Julian Anastasov <ja@ssi.bg>
+Date: Sat, 14 Feb 2026 16:58:49 +0200
+Subject: ipvs: skip ipv6 extension headers for csum checks
+
+From: Julian Anastasov <ja@ssi.bg>
+
+commit 05cfe9863ef049d98141dc2969eefde72fb07625 upstream.
+
+Protocol checksum validation fails for IPv6 if there are extension
+headers before the protocol header. iph->len already contains its
+offset, so use it to fix the problem.
+
+Fixes: 2906f66a5682 ("ipvs: SCTP Trasport Loadbalancing Support")
+Fixes: 0bbdd42b7efa ("IPVS: Extend protocol DNAT/SNAT and state handlers")
+Signed-off-by: Julian Anastasov <ja@ssi.bg>
+Signed-off-by: Florian Westphal <fw@strlen.de>
+Signed-off-by: Nazar Kalashnikov <nazarkalashnikov0@gmail.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ net/netfilter/ipvs/ip_vs_proto_sctp.c | 18 ++++++------------
+ net/netfilter/ipvs/ip_vs_proto_tcp.c | 21 +++++++--------------
+ net/netfilter/ipvs/ip_vs_proto_udp.c | 20 +++++++-------------
+ 3 files changed, 20 insertions(+), 39 deletions(-)
+
+--- a/net/netfilter/ipvs/ip_vs_proto_sctp.c
++++ b/net/netfilter/ipvs/ip_vs_proto_sctp.c
+@@ -10,7 +10,8 @@
+ #include <net/ip_vs.h>
+
+ static int
+-sctp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp);
++sctp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
++ unsigned int sctphoff);
+
+ static int
+ sctp_conn_schedule(struct netns_ipvs *ipvs, int af, struct sk_buff *skb,
+@@ -108,7 +109,7 @@ sctp_snat_handler(struct sk_buff *skb, s
+ int ret;
+
+ /* Some checks before mangling */
+- if (!sctp_csum_check(cp->af, skb, pp))
++ if (!sctp_csum_check(cp->af, skb, pp, sctphoff))
+ return 0;
+
+ /* Call application helper if needed */
+@@ -156,7 +157,7 @@ sctp_dnat_handler(struct sk_buff *skb, s
+ int ret;
+
+ /* Some checks before mangling */
+- if (!sctp_csum_check(cp->af, skb, pp))
++ if (!sctp_csum_check(cp->af, skb, pp, sctphoff))
+ return 0;
+
+ /* Call application helper if needed */
+@@ -185,19 +186,12 @@ sctp_dnat_handler(struct sk_buff *skb, s
+ }
+
+ static int
+-sctp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp)
++sctp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
++ unsigned int sctphoff)
+ {
+- unsigned int sctphoff;
+ struct sctphdr *sh;
+ __le32 cmp, val;
+
+-#ifdef CONFIG_IP_VS_IPV6
+- if (af == AF_INET6)
+- sctphoff = sizeof(struct ipv6hdr);
+- else
+-#endif
+- sctphoff = ip_hdrlen(skb);
+-
+ sh = (struct sctphdr *)(skb->data + sctphoff);
+ cmp = sh->checksum;
+ val = sctp_compute_cksum(skb, sctphoff);
+--- a/net/netfilter/ipvs/ip_vs_proto_tcp.c
++++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c
+@@ -29,7 +29,8 @@
+ #include <net/ip_vs.h>
+
+ static int
+-tcp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp);
++tcp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
++ unsigned int tcphoff);
+
+ static int
+ tcp_conn_schedule(struct netns_ipvs *ipvs, int af, struct sk_buff *skb,
+@@ -166,7 +167,7 @@ tcp_snat_handler(struct sk_buff *skb, st
+ int ret;
+
+ /* Some checks before mangling */
+- if (!tcp_csum_check(cp->af, skb, pp))
++ if (!tcp_csum_check(cp->af, skb, pp, tcphoff))
+ return 0;
+
+ /* Call application helper if needed */
+@@ -244,7 +245,7 @@ tcp_dnat_handler(struct sk_buff *skb, st
+ int ret;
+
+ /* Some checks before mangling */
+- if (!tcp_csum_check(cp->af, skb, pp))
++ if (!tcp_csum_check(cp->af, skb, pp, tcphoff))
+ return 0;
+
+ /*
+@@ -301,17 +302,9 @@ tcp_dnat_handler(struct sk_buff *skb, st
+
+
+ static int
+-tcp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp)
++tcp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
++ unsigned int tcphoff)
+ {
+- unsigned int tcphoff;
+-
+-#ifdef CONFIG_IP_VS_IPV6
+- if (af == AF_INET6)
+- tcphoff = sizeof(struct ipv6hdr);
+- else
+-#endif
+- tcphoff = ip_hdrlen(skb);
+-
+ switch (skb->ip_summed) {
+ case CHECKSUM_NONE:
+ skb->csum = skb_checksum(skb, tcphoff, skb->len - tcphoff, 0);
+@@ -322,7 +315,7 @@ tcp_csum_check(int af, struct sk_buff *s
+ if (csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
+ &ipv6_hdr(skb)->daddr,
+ skb->len - tcphoff,
+- ipv6_hdr(skb)->nexthdr,
++ IPPROTO_TCP,
+ skb->csum)) {
+ IP_VS_DBG_RL_PKT(0, af, pp, skb, 0,
+ "Failed checksum for");
+--- a/net/netfilter/ipvs/ip_vs_proto_udp.c
++++ b/net/netfilter/ipvs/ip_vs_proto_udp.c
+@@ -25,7 +25,8 @@
+ #include <net/ip6_checksum.h>
+
+ static int
+-udp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp);
++udp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
++ unsigned int udphoff);
+
+ static int
+ udp_conn_schedule(struct netns_ipvs *ipvs, int af, struct sk_buff *skb,
+@@ -155,7 +156,7 @@ udp_snat_handler(struct sk_buff *skb, st
+ int ret;
+
+ /* Some checks before mangling */
+- if (!udp_csum_check(cp->af, skb, pp))
++ if (!udp_csum_check(cp->af, skb, pp, udphoff))
+ return 0;
+
+ /*
+@@ -238,7 +239,7 @@ udp_dnat_handler(struct sk_buff *skb, st
+ int ret;
+
+ /* Some checks before mangling */
+- if (!udp_csum_check(cp->af, skb, pp))
++ if (!udp_csum_check(cp->af, skb, pp, udphoff))
+ return 0;
+
+ /*
+@@ -297,17 +298,10 @@ udp_dnat_handler(struct sk_buff *skb, st
+
+
+ static int
+-udp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp)
++udp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
++ unsigned int udphoff)
+ {
+ struct udphdr _udph, *uh;
+- unsigned int udphoff;
+-
+-#ifdef CONFIG_IP_VS_IPV6
+- if (af == AF_INET6)
+- udphoff = sizeof(struct ipv6hdr);
+- else
+-#endif
+- udphoff = ip_hdrlen(skb);
+
+ uh = skb_header_pointer(skb, udphoff, sizeof(_udph), &_udph);
+ if (uh == NULL)
+@@ -325,7 +319,7 @@ udp_csum_check(int af, struct sk_buff *s
+ if (csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
+ &ipv6_hdr(skb)->daddr,
+ skb->len - udphoff,
+- ipv6_hdr(skb)->nexthdr,
++ IPPROTO_UDP,
+ skb->csum)) {
+ IP_VS_DBG_RL_PKT(0, af, pp, skb, 0,
+ "Failed checksum for");