Separate IPv4 and IPv6 configuration

After recent changes, conf_ip() now has essentially entirely disjoint paths
for IPv4 and IPv6 configuration.  So, it's cleaner to split them out into
different functions conf_ip4() and conf_ip6().

Splitting these out also lets us make the interface a bit nicer, having
them return success or failure directly, rather than manipulating c->v4
and c->v6 to indicate success/failure of the two versions.

Since these functions may also initialize the interface index for each
protocol, it turns out we can then drop c->v4 and c->v6 entirely, replacing
tests on those with tests on whether c->ifi4 or c->ifi6 is non-zero (since
a 0 interface index is never valid).

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

7 files changed, 102 insertions, 94 deletions

diff --git a/conf.c b/conf.c
index 2b3263f..735b722 100644
--- a/conf.c
+++ b/conf.c
@@ -411,8 +411,8 @@ static void get_dns(struct ctx *c)
 	int line_len;
 	char *line, *p, *end;
 
-	dns4_set = !c->v4  || !!*dns4;
-	dns6_set = !c->v6  || !IN6_IS_ADDR_UNSPECIFIED(dns6);
+	dns4_set = !c->ifi4 || !!*dns4;
+	dns6_set = !c->ifi6 || !IN6_IS_ADDR_UNSPECIFIED(dns6);
 	dnss_set = !!*s->n || c->no_dns_search;
 	dns_set = (dns4_set && dns6_set) || c->no_dns;
 
@@ -611,87 +611,93 @@ static int conf_ns_opt(struct ctx *c,
 }
 
 /**
- * conf_ip() - Verify or detect IPv4/IPv6 support, get relevant addresses
+ * conf_ip4() - Verify or detect IPv4 support, get relevant addresses
  * @c:		Execution context
+ * @ifi:	Host interface to attempt (0 to determine one)
+ *
+ * Return:	Interface index for IPv4, or 0 on failure.
  */
-static void conf_ip(struct ctx *c)
+static unsigned int conf_ip4(struct ctx *c, unsigned int ifi)
 {
-	if (c->v4) {
-		if (!c->ifi4)
-			c->ifi4 = nl_get_ext_if(AF_INET);
-		if (!c->ifi4) {
-			warn("No external routable interface for IPv4");
-			c->v4 = 0;
-		}
-	}
+	if (!ifi)
+		ifi = nl_get_ext_if(AF_INET);
 
-	if (c->v6) {
-		if (!c->ifi6)
-			c->ifi6 = nl_get_ext_if(AF_INET6);
-		if (!c->ifi6) {
-			warn("No external routable interface for IPv6");
-			c->v6 = 0;
-		}
+	if (!ifi) {
+		warn("No external routable interface for IPv4");
+		return 0;
 	}
 
-	if (c->v4) {
-		if (!c->gw4)
-			nl_route(0, c->ifi4, AF_INET, &c->gw4);
+	if (!c->gw4)
+		nl_route(0, ifi, AF_INET, &c->gw4);
 
-		if (!c->addr4) {
-			int mask_len = 0;
+	if (!c->addr4) {
+		int mask_len = 0;
 
-			nl_addr(0, c->ifi4, AF_INET, &c->addr4, &mask_len, NULL);
-			c->mask4 = htonl(0xffffffff << (32 - mask_len));
-		}
+		nl_addr(0, ifi, AF_INET, &c->addr4, &mask_len, NULL);
+		c->mask4 = htonl(0xffffffff << (32 - mask_len));
+	}
 
-		if (!c->mask4) {
-			if (IN_CLASSA(ntohl(c->addr4)))
-				c->mask4 = htonl(IN_CLASSA_NET);
-			else if (IN_CLASSB(ntohl(c->addr4)))
-				c->mask4 = htonl(IN_CLASSB_NET);
-			else if (IN_CLASSC(ntohl(c->addr4)))
-				c->mask4 = htonl(IN_CLASSC_NET);
-			else
-				c->mask4 = 0xffffffff;
-		}
+	if (!c->mask4) {
+		if (IN_CLASSA(ntohl(c->addr4)))
+			c->mask4 = htonl(IN_CLASSA_NET);
+		else if (IN_CLASSB(ntohl(c->addr4)))
+			c->mask4 = htonl(IN_CLASSB_NET);
+		else if (IN_CLASSC(ntohl(c->addr4)))
+			c->mask4 = htonl(IN_CLASSC_NET);
+		else
+			c->mask4 = 0xffffffff;
+	}
 
-		memcpy(&c->addr4_seen, &c->addr4, sizeof(c->addr4_seen));
+	memcpy(&c->addr4_seen, &c->addr4, sizeof(c->addr4_seen));
 
-		if (MAC_IS_ZERO(c->mac))
-			nl_link(0, c->ifi4, c->mac, 0, 0);
-	}
+	if (MAC_IS_ZERO(c->mac))
+		nl_link(0, ifi, c->mac, 0, 0);
 
-	if (c->v6) {
-		int prefix_len = 0;
+	if (!c->gw4 || !c->addr4 || MAC_IS_ZERO(c->mac))
+		return 0;
 
-		if (IN6_IS_ADDR_UNSPECIFIED(&c->gw6))
-			nl_route(0, c->ifi6, AF_INET6, &c->gw6);
+	return ifi;
+}
 
-		nl_addr(0, c->ifi6, AF_INET6,
-			IN6_IS_ADDR_UNSPECIFIED(&c->addr6) ? &c->addr6 : NULL,
-			&prefix_len, &c->addr6_ll);
+/**
+ * conf_ip6() - Verify or detect IPv6 support, get relevant addresses
+ * @c:		Execution context
+ * @ifi:	Host interface to attempt (0 to determine one)
+ *
+ * Return:	Interface index for IPv6, or 0 on failure.
+ */
+static unsigned int conf_ip6(struct ctx *c, unsigned int ifi)
+{
+	int prefix_len = 0;
 
-		memcpy(&c->addr6_seen, &c->addr6, sizeof(c->addr6));
-		memcpy(&c->addr6_ll_seen, &c->addr6_ll, sizeof(c->addr6_ll));
+	if (!ifi)
+		ifi = nl_get_ext_if(AF_INET6);
 
-		if (MAC_IS_ZERO(c->mac))
-			nl_link(0, c->ifi6, c->mac, 0, 0);
+	if (!ifi) {
+		warn("No external routable interface for IPv6");
+		return 0;
 	}
 
-	if (!c->gw4 || !c->addr4 || MAC_IS_ZERO(c->mac))
-		c->v4 = 0;
+	if (IN6_IS_ADDR_UNSPECIFIED(&c->gw6))
+		nl_route(0, ifi, AF_INET6, &c->gw6);
+
+	nl_addr(0, ifi, AF_INET6,
+		IN6_IS_ADDR_UNSPECIFIED(&c->addr6) ? &c->addr6 : NULL,
+		&prefix_len, &c->addr6_ll);
+
+	memcpy(&c->addr6_seen, &c->addr6, sizeof(c->addr6));
+	memcpy(&c->addr6_ll_seen, &c->addr6_ll, sizeof(c->addr6_ll));
+
+	if (MAC_IS_ZERO(c->mac))
+		nl_link(0, ifi, c->mac, 0, 0);
 
 	if (IN6_IS_ADDR_UNSPECIFIED(&c->gw6) ||
 	    IN6_IS_ADDR_UNSPECIFIED(&c->addr6) ||
 	    IN6_IS_ADDR_UNSPECIFIED(&c->addr6_ll) ||
 	    MAC_IS_ZERO(c->mac))
-		c->v6 = 0;
+		return 0;
 
-	if (!c->v4 && !c->v6) {
-		err("External interface not usable");
-		exit(EXIT_FAILURE);
-	}
+	return ifi;
 }
 
 /**
@@ -889,7 +895,7 @@ static void conf_print(const struct ctx *c)
 	     c->mac[0], c->mac[1], c->mac[2],
 	     c->mac[3], c->mac[4], c->mac[5]);
 
-	if (c->v4) {
+	if (c->ifi4) {
 		if (!c->no_dhcp) {
 			info("DHCP:");
 			info("    assign: %s",
@@ -914,7 +920,7 @@ static void conf_print(const struct ctx *c)
 		}
 	}
 
-	if (c->v6) {
+	if (c->ifi6) {
 		char buf6[INET6_ADDRSTRLEN];
 
 		if (!c->no_ndp && !c->no_dhcpv6)
@@ -1063,6 +1069,7 @@ void conf(struct ctx *c, int argc, char **argv)
 	struct in6_addr *dns6 = c->dns6;
 	int name, ret, mask, b, i;
 	uint32_t *dns4 = c->dns4;
+	unsigned int ifi = 0;
 
 	if (c->mode == MODE_PASTA)
 		c->no_dhcp_dns = c->no_dhcp_dns_search = 1;
@@ -1390,12 +1397,12 @@ void conf(struct ctx *c, int argc, char **argv)
 			usage(argv[0]);
 			break;
 		case 'i':
-			if (c->ifi4 || c->ifi6) {
+			if (ifi) {
 				err("Redundant interface: %s", optarg);
 				usage(argv[0]);
 			}
 
-			if (!(c->ifi4 = c->ifi6 = if_nametoindex(optarg))) {
+			if (!(ifi = if_nametoindex(optarg))) {
 				err("Invalid interface name %s: %s", optarg,
 				    strerror(errno));
 				usage(argv[0]);
@@ -1503,9 +1510,14 @@ void conf(struct ctx *c, int argc, char **argv)
 		err("Options ipv4-only and ipv6-only are mutually exclusive");
 		usage(argv[0]);
 	}
-	c->v4 = !v6_only;
-	c->v6 = !v4_only;
-	conf_ip(c);
+	if (!v6_only)
+		c->ifi4 = conf_ip4(c, ifi);
+	if (!v4_only)
+		c->ifi6 = conf_ip6(c, ifi);
+	if (!c->ifi4 && !c->ifi6) {
+		err("External interface not usable");
+		exit(EXIT_FAILURE);
+	}
 
 	/* Now we can process port configuration options */
 	optind = 1;
@@ -1542,10 +1554,10 @@ void conf(struct ctx *c, int argc, char **argv)
 		}
 	} while (name != -1);
 
-	if (!c->v4)
+	if (!c->ifi4)
 		c->no_dhcp = 1;
 
-	if (!c->v6) {
+	if (!c->ifi6) {
 		c->no_ndp = 1;
 		c->no_dhcpv6 = 1;
 	}
diff --git a/passt.c b/passt.c
index 01eed1b..5d0b3cd 100644
--- a/passt.c
+++ b/passt.c
@@ -365,10 +365,10 @@ int main(int argc, char **argv)
 
 	proto_update_l2_buf(c.mac_guest, c.mac, &c.addr4);
 
-	if (c.v4 && !c.no_dhcp)
+	if (c.ifi4 && !c.no_dhcp)
 		dhcp_init();
 
-	if (c.v6 && !c.no_dhcpv6)
+	if (c.ifi6 && !c.no_dhcpv6)
 		dhcpv6_init(&c);
 
 	if (c.debug)
diff --git a/passt.h b/passt.h
index 23145c6..a8d5992 100644
--- a/passt.h
+++ b/passt.h
@@ -121,8 +121,7 @@ enum passt_modes {
  * @fd_tap:		File descriptor for AF_UNIX socket or tuntap device
  * @mac:		Host MAC address
  * @mac_guest:		MAC address of guest or namespace, seen or configured
- * @v4:			Enable IPv4 transport
- * @ifi4:		Index of routable interface for IPv4
+ * @ifi4:		Index of routable interface for IPv4, 0 if IPv4 disabled
  * @addr4:		IPv4 address for external, routable interface
  * @addr4_seen:		Latest IPv4 address seen as source from tap
  * @mask4:		IPv4 netmask, network order
@@ -130,8 +129,7 @@ enum passt_modes {
  * @dns4:		IPv4 DNS addresses, zero-terminated, network order
  * @dns4_fwd:		Address forwarded (UDP) to first IPv4 DNS, network order
  * @dns_search:		DNS search list
- * @v6:			Enable IPv6 transport
- * @ifi6:		Index of routable interface for IPv6
+ * @ifi6:		Index of routable interface for IPv6, 0 if IPv6 disabled
  * @addr6:		IPv6 address for external, routable interface
  * @addr6_ll:		Link-local IPv6 address on external, routable interface
  * @addr6_seen:		Latest IPv6 global/site address seen as source from tap
@@ -193,7 +191,6 @@ struct ctx {
 	unsigned char mac[ETH_ALEN];
 	unsigned char mac_guest[ETH_ALEN];
 
-	int v4;
 	unsigned int ifi4;
 	uint32_t addr4;
 	uint32_t addr4_seen;
@@ -204,7 +201,6 @@ struct ctx {
 
 	struct fqdn dns_search[MAXDNSRCH];
 
-	int v6;
 	unsigned int ifi6;
 	struct in6_addr addr6;
 	struct in6_addr addr6_ll;
diff --git a/pasta.c b/pasta.c
index cd37d16..2d7b5a1 100644
--- a/pasta.c
+++ b/pasta.c
@@ -195,14 +195,14 @@ void pasta_ns_conf(struct ctx *c)
 
 		nl_link(1, c->pasta_ifi, c->mac_guest, 1, c->mtu);
 
-		if (c->v4) {
+		if (c->ifi4) {
 			prefix_len = __builtin_popcount(c->mask4);
 			nl_addr(1, c->pasta_ifi, AF_INET, &c->addr4,
 				&prefix_len, NULL);
 			nl_route(1, c->pasta_ifi, AF_INET, &c->gw4);
 		}
 
-		if (c->v6) {
+		if (c->ifi6) {
 			prefix_len = 64;
 			nl_addr(1, c->pasta_ifi, AF_INET6, &c->addr6,
 				&prefix_len, NULL);
diff --git a/tap.c b/tap.c
index 43a7372..8d552e9 100644
--- a/tap.c
+++ b/tap.c
@@ -318,7 +318,7 @@ static int tap4_handler(struct ctx *c, const struct pool *in,
 	unsigned int i, j, seq_count;
 	struct tap4_l4_t *seq;
 
-	if (!c->v4 || !in->count)
+	if (!c->ifi4 || !in->count)
 		return in->count;
 
 	i = 0;
@@ -471,7 +471,7 @@ static int tap6_handler(struct ctx *c, const struct pool *in,
 	unsigned int i, j, seq_count = 0;
 	struct tap6_l4_t *seq;
 
-	if (!c->v6 || !in->count)
+	if (!c->ifi6 || !in->count)
 		return in->count;
 
 	i = 0;
diff --git a/tcp.c b/tcp.c
index 3b27f11..3382dfd 100644
--- a/tcp.c
+++ b/tcp.c
@@ -3252,7 +3252,7 @@ static int tcp_sock_refill(void *arg)
 		p6 = init_sock_pool6;
 	}
 
-	for (i = 0; a->c->v4 && i < TCP_SOCK_POOL_SIZE; i++, p4++) {
+	for (i = 0; a->c->ifi4 && i < TCP_SOCK_POOL_SIZE; i++, p4++) {
 		if (*p4 >= 0)
 			break;
 
@@ -3267,7 +3267,7 @@ static int tcp_sock_refill(void *arg)
 			tcp_sock_set_bufsize(a->c, *p4);
 	}
 
-	for (i = 0; a->c->v6 && i < TCP_SOCK_POOL_SIZE; i++, p6++) {
+	for (i = 0; a->c->ifi6 && i < TCP_SOCK_POOL_SIZE; i++, p6++) {
 		if (*p6 >= 0)
 			break;
 
@@ -3327,10 +3327,10 @@ int tcp_init(struct ctx *c)
 	for (i = 0; i < ARRAY_SIZE(tcp_l2_mh); i++)
 		tcp_l2_mh[i] = (struct mmsghdr) { .msg_hdr.msg_iovlen = 1 };
 
-	if (c->v4)
+	if (c->ifi4)
 		tcp_sock4_iov_init();
 
-	if (c->v6)
+	if (c->ifi6)
 		tcp_sock6_iov_init();
 
 	memset(init_sock_pool4,		0xff,	sizeof(init_sock_pool4));
@@ -3431,8 +3431,8 @@ static int tcp_port_rebind(void *arg)
 			if (bitmap_isset(a->c->tcp.port_to_tap, port))
 				continue;
 
-			if ((a->c->v4 && tcp_sock_ns[port][V4] == -1) ||
-			    (a->c->v6 && tcp_sock_ns[port][V6] == -1))
+			if ((a->c->ifi4 && tcp_sock_ns[port][V4] == -1) ||
+			    (a->c->ifi6 && tcp_sock_ns[port][V6] == -1))
 				tcp_sock_init(a->c, 1, AF_UNSPEC, NULL, port);
 		}
 	} else {
@@ -3464,8 +3464,8 @@ static int tcp_port_rebind(void *arg)
 			if (bitmap_isset(a->c->tcp.port_to_init, port))
 				continue;
 
-			if ((a->c->v4 && tcp_sock_init_ext[port][V4] == -1) ||
-			    (a->c->v6 && tcp_sock_init_ext[port][V6] == -1))
+			if ((a->c->ifi4 && tcp_sock_init_ext[port][V4] == -1) ||
+			    (a->c->ifi6 && tcp_sock_init_ext[port][V6] == -1))
 				tcp_sock_init(a->c, 0, AF_UNSPEC, NULL, port);
 		}
 	}
@@ -3512,8 +3512,8 @@ void tcp_timer(struct ctx *c, const struct timespec *ts)
 	tcp_sock_refill(&refill_arg);
 	if (c->mode == MODE_PASTA) {
 		refill_arg.ns = 1;
-		if ((c->v4 && ns_sock_pool4[TCP_SOCK_POOL_TSH] < 0) ||
-		    (c->v6 && ns_sock_pool6[TCP_SOCK_POOL_TSH] < 0))
+		if ((c->ifi4 && ns_sock_pool4[TCP_SOCK_POOL_TSH] < 0) ||
+		    (c->ifi6 && ns_sock_pool6[TCP_SOCK_POOL_TSH] < 0))
 			NS_CALL(tcp_sock_refill, &refill_arg);
 
 		tcp_splice_timer(c);
diff --git a/udp.c b/udp.c
index 98e3eaa..856429f 100644
--- a/udp.c
+++ b/udp.c
@@ -1266,10 +1266,10 @@ static void udp_splice_iov_init(void)
  */
 int udp_init(const struct ctx *c)
 {
-	if (c->v4)
+	if (c->ifi4)
 		udp_sock4_iov_init();
 
-	if (c->v6)
+	if (c->ifi6)
 		udp_sock6_iov_init();
 
 	if (c->mode == MODE_PASTA) {
@@ -1341,7 +1341,7 @@ void udp_timer(struct ctx *c, const struct timespec *ts)
 	unsigned int i;
 	long *word, tmp;
 
-	if (!c->v4)
+	if (!c->ifi4)
 		v6 = 1;
 v6:
 	for (t = 0; t < UDP_ACT_TYPE_MAX; t++) {
@@ -1356,7 +1356,7 @@ v6:
 		}
 	}
 
-	if (!v6 && c->v6) {
+	if (!v6 && c->ifi6) {
 		v6 = 1;
 		goto v6;
 	}