selftests: net: csum: Clean up recv_verify_packet_ipv6

Rename ip_len to payload_len since the length in this case refers only
to the payload, and not the entire IP packet like for IPv4. While we're
at it, just use the variable directly when calling
recv_verify_packet_udp/tcp.

Signed-off-by: Sean Anderson <[e-mail]>
Reviewed-by: Willem de Bruijn <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/lib/csum.c

···
 {
 	struct ipv6hdr *ip6h = nh;
 	uint16_t proto = cfg_encap ? IPPROTO_UDP : cfg_proto;
-	uint16_t ip_len;
+	uint16_t payload_len;
 
 	if (len < sizeof(*ip6h) || ip6h->nexthdr != proto)
 		return -1;
 
-	ip_len = ntohs(ip6h->payload_len);
-	if (ip_len > len - sizeof(*ip6h))
+	payload_len = ntohs(ip6h->payload_len);
+	if (payload_len > len - sizeof(*ip6h))
 		return -1;
 
-	len = ip_len;
 	iph_addr_p = &ip6h->saddr;
-
 	if (proto == IPPROTO_TCP)
-		return recv_verify_packet_tcp(ip6h + 1, len);
+		return recv_verify_packet_tcp(ip6h + 1, payload_len);
 	else
-		return recv_verify_packet_udp(ip6h + 1, len);
+		return recv_verify_packet_udp(ip6h + 1, payload_len);
 }
 
 /* return whether auxdata includes TP_STATUS_CSUM_VALID */