set_sctp_state() reads the SCTP chunk header again in order to drive the IPVS SCTP state table. For IPv6 it computes the offset with sizeof(struct ipv6hdr), while the surrounding IPVS code uses iph->len from ip_vs_fill_iph_skb(), where ipv6_find_hdr() has already skipped extension headers and found the real transport header. This makes the state machine read from the wrong offset for IPv6 SCTP packets that carry extension headers. For example, an INIT packet with an 8-byte destination options header can be scheduled correctly by sctp_conn_schedule(), but set_sctp_state() reads the first byte of the SCTP verification tag as a DATA chunk type. The connection then moves from NONE to ESTABLISHED instead of INIT1, gets the longer established timeout, and updates the active/inactive destination counters incorrectly. This happens even though the SCTP handshake has not completed. Use ip_vs_fill_iph_skb() in set_sctp_state() and base the chunk-header offset on iph.len, matching sctp_conn_schedule() and the SCTP NAT handlers. For IPv4 and IPv6 packets without extension headers this preserves the existing offset. Fixes: 2906f66a5682 ("ipvs: SCTP Trasport Loadbalancing Support") Cc: stable@vger.kernel.org Reported-by: Yizhou Zhao Reported-by: Yuxiang Yang Reported-by: Ao Wang Reported-by: Xuewei Feng Reported-by: Qi Li Reported-by: Ke Xu Assisted-by: Claude-Code:GLM-5.2 Signed-off-by: Yizhou Zhao --- net/netfilter/ipvs/ip_vs_proto_sctp.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/net/netfilter/ipvs/ip_vs_proto_sctp.c b/net/netfilter/ipvs/ip_vs_proto_sctp.c index 63c78a1f3918..6e0fc23be305 100644 --- a/net/netfilter/ipvs/ip_vs_proto_sctp.c +++ b/net/netfilter/ipvs/ip_vs_proto_sctp.c @@ -375,17 +375,15 @@ set_sctp_state(struct ip_vs_proto_data *pd, struct ip_vs_conn *cp, int direction, const struct sk_buff *skb) { struct sctp_chunkhdr _sctpch, *sch; unsigned char chunk_type; + struct ip_vs_iphdr iph; int event, next_state; - int ihl, cofs; + int cofs; -#ifdef CONFIG_IP_VS_IPV6 - ihl = cp->af == AF_INET ? ip_hdrlen(skb) : sizeof(struct ipv6hdr); -#else - ihl = ip_hdrlen(skb); -#endif + if (!ip_vs_fill_iph_skb(cp->af, skb, false, &iph)) + return; - cofs = ihl + sizeof(struct sctphdr); + cofs = iph.len + sizeof(struct sctphdr); sch = skb_header_pointer(skb, cofs, sizeof(_sctpch), &_sctpch); if (sch == NULL) return; -- 2.47.3