Split tap_ip_send() into IPv4 and IPv6 specific functions

The IPv4 and IPv6 paths in tap_ip_send() have very little in common, and
it turns out that every caller (statically) knows if it is using IPv4 or
IPv6.  So split into separate tap_ip4_send() and tap_ip6_send() functions.
Use a new tap_l2_hdr() function for the very small common part.

While we're there, make some minor cleanups:
  - We were double writing some fields in the IPv6 header, so that it
    temporary matched the pseudo-header for checksum calculation.  With
    recent checksum reworks, this isn't neccessary any more.
  - We don't use any IPv4 header options, so use some sizeof() constructs
    instead of some open coded values for header length.
  - The comment used to say that the flow label was for TCP over IPv6, but
    in fact the only thing we used it for was DHCPv6 over UDP traffic

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

1 files changed, 3 insertions, 3 deletions

diff --git a/dhcpv6.c b/dhcpv6.c
index e7640ce..7829968 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -531,8 +531,8 @@ int dhcpv6(struct ctx *c, const struct pool *p,
 
 			resp_not_on_link.hdr.xid = mh->xid;
 
-			tap_ip_send(c, src, IPPROTO_UDP,
-				    (char *)&resp_not_on_link, n, mh->xid);
+			tap_ip6_send(c, src, IPPROTO_UDP,
+				     (char *)&resp_not_on_link, n, mh->xid);
 
 			return 1;
 		}
@@ -580,7 +580,7 @@ int dhcpv6(struct ctx *c, const struct pool *p,
 
 	resp.hdr.xid = mh->xid;
 
-	tap_ip_send(c, src, IPPROTO_UDP, (char *)&resp, n, mh->xid);
+	tap_ip6_send(c, src, IPPROTO_UDP, (char *)&resp, n, mh->xid);
 	c->ip6.addr_seen = c->ip6.addr;
 
 	return 1;