tap: Split tap_ip4_send() into UDP and ICMP variants

tap_ip4_send() has special case logic to compute the checksums for UDP
and ICMP packets, which is a mild layering violation.  By using a suitable
helper we can split it into tap_udp4_send() and tap_icmp4_send() functions
without greatly increasing the code size, this removing that layering
violation.

We make some small changes to the interface while there.  In both cases
we make the destination IPv4 address a parameter, which will be useful
later.  For the UDP variant we make it take just the UDP payload, and it
will generate the UDP header.  For the ICMP variant we pass in the ICMP
header as before.  The inconsistency is because that's what seems to be
the more natural way to invoke the function in the callers in each case.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/tap.h b/tap.h
index d43c7a0..743bc58 100644
--- a/tap.h
+++ b/tap.h
@@ -7,10 +7,13 @@
 #define TAP_H
 
 in_addr_t tap_ip4_daddr(const struct ctx *c);
+void tap_udp4_send(const struct ctx *c, in_addr_t src, in_port_t sport,
+		   in_addr_t dst, in_port_t dport,
+		   const void *in, size_t len);
+void tap_icmp4_send(const struct ctx *c, in_addr_t src, in_addr_t dst,
+		    void *in, size_t len);
 const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
 				     const struct in6_addr *src);
-void tap_ip4_send(const struct ctx *c, in_addr_t src, uint8_t proto,
-		  const char *in, size_t len);
 void tap_udp6_send(const struct ctx *c,
 		   const struct in6_addr *src, in_port_t sport,
 		   const struct in6_addr *dst, in_port_t dport,