conntrack: Fix L4 csum for V6 extension hdr pkts.

It is a day one issue that got copied to subsequent code.

Fixes: a489b16 ("conntrack: New userspace connection tracker.")
Fixes: bd5e81a ("Userspace Datapath: Add ALG infra and FTP.")
CC: Daniele Di Proietto <diproiettod@ovn.org>
Signed-off-by: Darrell Ball <dlu998@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

lib/conntrack.c

@@ -687,10 +687,9 @@ reverse_nat_packet(struct dp_packet *pkt, const struct conn *conn)
                                  true);
         }
         reverse_pat_packet(pkt, conn);
-        uint32_t icmp6_csum = packet_csum_pseudoheader6(nh6);
         icmp6->icmp6_base.icmp6_cksum = 0;
-        icmp6->icmp6_base.icmp6_cksum = csum_finish(
-            csum_continue(icmp6_csum, icmp6, tail - (char *) icmp6 - pad));
+        icmp6->icmp6_base.icmp6_cksum = packet_csum_upperlayer6(nh6, icmp6,
+            IPPROTO_ICMPV6, tail - (char *) icmp6 - pad);
     }
     pkt->l3_ofs = orig_l3_ofs;
     pkt->l4_ofs = orig_l4_ofs;
@@ -1582,19 +1581,14 @@ static inline bool
 checksum_valid(const struct conn_key *key, const void *data, size_t size,
                const void *l3)
 {
-    uint32_t csum = 0;
-
     if (key->dl_type == htons(ETH_TYPE_IP)) {
-        csum = packet_csum_pseudoheader(l3);
+        uint32_t csum = packet_csum_pseudoheader(l3);
+        return csum_finish(csum_continue(csum, data, size)) == 0;
     } else if (key->dl_type == htons(ETH_TYPE_IPV6)) {
-        csum = packet_csum_pseudoheader6(l3);
+        return packet_csum_upperlayer6(l3, data, key->nw_proto, size) == 0;
     } else {
         return false;
     }
-
-    csum = csum_continue(csum, data, size);
-
-    return csum_finish(csum) == 0;
 }
 
 static inline bool
@@ -3256,16 +3250,14 @@ handle_ftp_ctl(struct conntrack *ct, const struct conn_lookup_ctx *ctx,
     }
 
     th->tcp_csum = 0;
-    uint32_t tcp_csum;
     if (ctx->key.dl_type == htons(ETH_TYPE_IPV6)) {
-        tcp_csum = packet_csum_pseudoheader6(nh6);
+        th->tcp_csum = packet_csum_upperlayer6(nh6, th, ctx->key.nw_proto,
+                           dp_packet_l4_size(pkt));
     } else {
-        tcp_csum = packet_csum_pseudoheader(l3_hdr);
+        uint32_t tcp_csum = packet_csum_pseudoheader(l3_hdr);
+        th->tcp_csum = csum_finish(
+             csum_continue(tcp_csum, th, dp_packet_l4_size(pkt)));
     }
-    const char *tail = dp_packet_tail(pkt);
-    uint8_t pad = dp_packet_l2_pad_size(pkt);
-    th->tcp_csum = csum_finish(
-        csum_continue(tcp_csum, th, tail - (char *) th - pad));
 
     if (seq_skew) {
         conn_seq_skew_set(ct, &ec->key, now, seq_skew + ec->seq_skew,