Add csum_icmp6() helper for calculating ICMPv6 checksums

At least two places in passt calculate ICMPv6 checksums, ndp() and
tap_ip_send().  Add a helper to handle this calculation in both places.
For future flexibility, the new helper takes parameters for the fields in
the IPv6 pseudo-header, so an IPv6 header or pseudo-header doesn't need to
be explicitly constructed.  It also allows the ICMPv6 header and payload to
be in separate buffers, although we don't use this yet.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 2 insertions, 4 deletions

diff --git a/tap.c b/tap.c
index 8b6d9bc..aafc92b 100644
--- a/tap.c
+++ b/tap.c
@@ -191,10 +191,8 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
 		} else if (proto == IPPROTO_ICMPV6) {
 			struct icmp6hdr *ih = (struct icmp6hdr *)(ip6h + 1);
 
-			ih->icmp6_cksum = 0;
-			ih->icmp6_cksum = csum_unaligned(ip6h,
-							 len + sizeof(*ip6h),
-							 0);
+			csum_icmp6(ih, &ip6h->saddr, &ip6h->daddr,
+				   ih + 1, len - sizeof(*ih));
 		}
 		ip6h->version = 6;
 		ip6h->nexthdr = proto;