net: ipv6: fix TCP GSO segmentation with NAT

When updating the source/destination address, the TCP/UDP checksum needs to
be updated as well.

Fixes: bee88cd5bd83 ("net: add support for segmenting TCP fraglist GSO packets")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://patch.msgid.link/20250311212530.91519-1-nbd@nbd.name
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/ipv6/tcpv6_offload.c b/net/ipv6/tcpv6_offload.c
index a45bf17cb2a172d4612cb42f51481b97bbf364cd..ae2da28f9dfb1c052b1f86ba37497a011621fea8 100644 (file)
--- a/net/ipv6/tcpv6_offload.c
+++ b/net/ipv6/tcpv6_offload.c
@@ -94,14 +94,23 @@ INDIRECT_CALLABLE_SCOPE int tcp6_gro_complete(struct sk_buff *skb, int thoff)
 }
 
 static void __tcpv6_gso_segment_csum(struct sk_buff *seg,
+                                    struct in6_addr *oldip,
+                                    const struct in6_addr *newip,
                                     __be16 *oldport, __be16 newport)
 {
-       struct tcphdr *th;
+       struct tcphdr *th = tcp_hdr(seg);
+
+       if (!ipv6_addr_equal(oldip, newip)) {
+               inet_proto_csum_replace16(&th->check, seg,
+                                         oldip->s6_addr32,
+                                         newip->s6_addr32,
+                                         true);
+               *oldip = *newip;
+       }
 
        if (*oldport == newport)
                return;
 
-       th = tcp_hdr(seg);
        inet_proto_csum_replace2(&th->check, seg, *oldport, newport, false);
        *oldport = newport;
 }
@@ -129,10 +138,10 @@ static struct sk_buff *__tcpv6_gso_segment_list_csum(struct sk_buff *segs)
                th2 = tcp_hdr(seg);
                iph2 = ipv6_hdr(seg);
 
-               iph2->saddr = iph->saddr;
-               iph2->daddr = iph->daddr;
-               __tcpv6_gso_segment_csum(seg, &th2->source, th->source);
-               __tcpv6_gso_segment_csum(seg, &th2->dest, th->dest);
+               __tcpv6_gso_segment_csum(seg, &iph2->saddr, &iph->saddr,
+                                        &th2->source, th->source);
+               __tcpv6_gso_segment_csum(seg, &iph2->daddr, &iph->daddr,
+                                        &th2->dest, th->dest);
        }
 
        return segs;