[PATCH v2 06/14] Add helpers for normal inbound packet destination addresses

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

tap_ip_send() doesn't take a destination address, because it's specifically
for inbound packets, and the IP addresses of the guest/namespace are
already known to us.  Rather than open-coding this destination address
logic, make helper functions for it which will enable some later cleanups.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 tap.c | 33 ++++++++++++++++++++++++++++-----
 tap.h |  3 +++
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/tap.c b/tap.c
index de02c56..89be383 100644
--- a/tap.c
+++ b/tap.c
@@ -96,6 +96,32 @@ int tap_send(const struct ctx *c, const void *data, size_t len, int vnet_pre)
 	return write(c->fd_tap, (char *)data + (vnet_pre ? 4 : 0), len);
 }
 
+/**
+ * tap_ip4_daddr() - Normal IPv4 destination address for inbound packets
+ * @c:		Execution context
+ *
+ * Returns: IPv4 address, network order
+ */
+in_addr_t tap_ip4_daddr(const struct ctx *c)
+{
+	return c->ip4.addr_seen;
+}
+
+/**
+ * tap_ip6_daddr() - Normal IPv4 destination address for inbound packets
+ * @c:		Execution context
+ * @src:	Source address
+ *
+ * Returns: pointer to IPv6 address
+ */
+const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
+				     const struct in6_addr *src)
+{
+	if (IN6_IS_ADDR_LINKLOCAL(src))
+		return &c->ip6.addr_ll_seen;
+	return &c->ip6.addr_seen;
+}
+
 /**
  * tap_ip_send() - Send IP packet, with L2 headers, calculating L3/L4 checksums
  * @c:		Execution context
@@ -132,7 +158,7 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
 		iph->frag_off = 0;
 		iph->ttl = 255;
 		iph->protocol = proto;
-		iph->daddr = c->ip4.addr_seen;
+		iph->daddr = tap_ip4_daddr(c);
 		memcpy(&iph->saddr, &src->s6_addr[12], 4);
 
 		csum_ip4_header(iph);
@@ -163,10 +189,7 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
 		ip6h->priority = 0;
 
 		ip6h->saddr = *src;
-		if (IN6_IS_ADDR_LINKLOCAL(src))
-			ip6h->daddr = c->ip6.addr_ll_seen;
-		else
-			ip6h->daddr = c->ip6.addr_seen;
+		ip6h->daddr = *tap_ip6_daddr(c, src);
 
 		memcpy(data, in, len);
 
diff --git a/tap.h b/tap.h
index df3aec0..a6764b4 100644
--- a/tap.h
+++ b/tap.h
@@ -6,6 +6,9 @@
 #ifndef TAP_H
 #define TAP_H
 
+in_addr_t tap_ip4_daddr(const struct ctx *c);
+const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
+				     const struct in6_addr *src);
 void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
 		 const char *in, size_t len, uint32_t flow);
 int tap_send(const struct ctx *c, const void *data, size_t len, int vnet_pre);
-- 
@@ -6,6 +6,9 @@
 #ifndef TAP_H
 #define TAP_H
 
+in_addr_t tap_ip4_daddr(const struct ctx *c);
+const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
+				     const struct in6_addr *src);
 void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
 		 const char *in, size_t len, uint32_t flow);
 int tap_send(const struct ctx *c, const void *data, size_t len, int vnet_pre);
-- 
2.37.3