[PATCH 6/6] udp: Clean up UDP checksum generation for inbound IPv6 packets

[David Gibson <david@gibson.dropbear.id.au>]

Currently we open code the calculation of the UDP checksum, which involves
temporarily mangling the IPv6 header to match the UDP checksum
pseudo-header.  It also assumes that the payload is contiguous with the
headers, which is true for now, but we want to change in future.

We already have a helper which correcly calculates UDP over IPv6 checksums,
which doesn't require temporarily modifying the headers and which handles
a non-contiguous payload, so use it.  It turns out we were already
initializing the IPv6 version, nexthdr and hop_limit fields, even though
we overwrote them for each packet here, so we can just leave those in
place now.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 udp.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/udp.c b/udp.c
index a0080b1a..ee1481f9 100644
--- a/udp.c
+++ b/udp.c
@@ -676,13 +676,7 @@ static size_t udp_update_hdr6(const struct ctx *c, struct udp6_l2_buf_t *b,
 	b->uh.source = htons(srcport);
 	b->uh.dest = htons(dstport);
 	b->uh.len = b->ip6h.payload_len;
-
-	b->ip6h.hop_limit = IPPROTO_UDP;
-	b->ip6h.version = b->ip6h.nexthdr = b->uh.check = 0;
-	b->uh.check = csum(&b->ip6h, ip_len, 0);
-	b->ip6h.version = 6;
-	b->ip6h.nexthdr = IPPROTO_UDP;
-	b->ip6h.hop_limit = 255;
+	csum_udp6(&b->uh, src, dst, b->data, datalen);
 
 	return tap_iov_len(c, &b->taph, ip_len);
 }
-- 
@@ -676,13 +676,7 @@ static size_t udp_update_hdr6(const struct ctx *c, struct udp6_l2_buf_t *b,
 	b->uh.source = htons(srcport);
 	b->uh.dest = htons(dstport);
 	b->uh.len = b->ip6h.payload_len;
-
-	b->ip6h.hop_limit = IPPROTO_UDP;
-	b->ip6h.version = b->ip6h.nexthdr = b->uh.check = 0;
-	b->uh.check = csum(&b->ip6h, ip_len, 0);
-	b->ip6h.version = 6;
-	b->ip6h.nexthdr = IPPROTO_UDP;
-	b->ip6h.hop_limit = 255;
+	csum_udp6(&b->uh, src, dst, b->data, datalen);
 
 	return tap_iov_len(c, &b->taph, ip_len);
 }
-- 
2.44.0