[PATCH v2 3/6] Use IPV4_IS_LOOPBACK more widely

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

This macro checks if an IPv4 address is in the loopback network
(127.0.0.0/8).  There are two places where we open code an identical check,
use the macro instead.

There are also a number of places we specifically exclude the loopback
address (127.0.0.1), but we should actually be excluding anything in the
loopback network.  Change those sites to use the macro as well.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 conf.c | 8 ++++----
 udp.c  | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/conf.c b/conf.c
index 6c2a9ad..c36403d 100644
--- a/conf.c
+++ b/conf.c
@@ -389,7 +389,7 @@ static void get_dns(struct ctx *c)
 			    dns4 - &c->ip4.dns[0] < ARRAY_SIZE(c->ip4.dns) - 1 &&
 			    inet_pton(AF_INET, p + 1, dns4)) {
 				/* We can only access local addresses via the gw redirect */
-				if (ntohl(*dns4) >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET) {
+				if (IPV4_IS_LOOPBACK(ntohl(*dns4))) {
 					if (c->no_map_gw) {
 						*dns4 = 0;
 						continue;
@@ -1190,7 +1190,7 @@ void conf(struct ctx *c, int argc, char **argv)
 			    inet_pton(AF_INET, optarg, &c->ip4.dns_fwd)	&&
 			    c->ip4.dns_fwd != htonl(INADDR_ANY)		&&
 			    c->ip4.dns_fwd != htonl(INADDR_BROADCAST)	&&
-			    c->ip4.dns_fwd != htonl(INADDR_LOOPBACK))
+			    !IPV4_IS_LOOPBACK(ntohl(c->ip4.dns_fwd)))
 				break;
 
 			err("Invalid DNS forwarding address: %s", optarg);
@@ -1389,7 +1389,7 @@ void conf(struct ctx *c, int argc, char **argv)
 			    inet_pton(AF_INET, optarg, &c->ip4.addr)	&&
 			    c->ip4.addr != htonl(INADDR_ANY)		&&
 			    c->ip4.addr != htonl(INADDR_BROADCAST)	&&
-			    c->ip4.addr != htonl(INADDR_LOOPBACK)	&&
+			    !IPV4_IS_LOOPBACK(ntohl(c->ip4.addr))	&&
 			    !IN_MULTICAST(ntohl(c->ip4.addr)))
 				break;
 
@@ -1425,7 +1425,7 @@ void conf(struct ctx *c, int argc, char **argv)
 			    inet_pton(AF_INET, optarg, &c->ip4.gw)	&&
 			    c->ip4.gw != htonl(INADDR_ANY)		&&
 			    c->ip4.gw != htonl(INADDR_BROADCAST)	&&
-			    c->ip4.gw != htonl(INADDR_LOOPBACK))
+			    !IPV4_IS_LOOPBACK(ntohl(c->ip4.gw)))
 				break;
 
 			err("Invalid gateway address: %s", optarg);
diff --git a/udp.c b/udp.c
index 4b201d3..7ce533d 100644
--- a/udp.c
+++ b/udp.c
@@ -680,7 +680,7 @@ static void udp_sock_fill_data_v4(const struct ctx *c, int n,
 	src = ntohl(b->s_in.sin_addr.s_addr);
 	src_port = ntohs(b->s_in.sin_port);
 
-	if (src >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET ||
+	if (IPV4_IS_LOOPBACK(src) ||
 	    src == INADDR_ANY || src == ntohl(c->ip4.addr_seen)) {
 		b->iph.saddr = c->ip4.gw;
 		udp_tap_map[V4][src_port].ts = now->tv_sec;
-- 
@@ -680,7 +680,7 @@ static void udp_sock_fill_data_v4(const struct ctx *c, int n,
 	src = ntohl(b->s_in.sin_addr.s_addr);
 	src_port = ntohs(b->s_in.sin_port);
 
-	if (src >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET ||
+	if (IPV4_IS_LOOPBACK(src) ||
 	    src == INADDR_ANY || src == ntohl(c->ip4.addr_seen)) {
 		b->iph.saddr = c->ip4.gw;
 		udp_tap_map[V4][src_port].ts = now->tv_sec;
-- 
2.38.1