netifd: Add interface config support to enable/disable IPv6 in the kernel per device

Main use case is being able to disable IPv6 on (a) WAN interface(s) when only IPv4 connectivity is offered or 6rd is used.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

1 files changed, 42 insertions, 2 deletions

diff --git a/system-linux.c b/system-linux.c
index 7cec649..8f46705 100644
--- a/system-linux.c
+++ b/system-linux.c
@@ -211,6 +211,40 @@ static void system_set_disable_ipv6(struct device *dev, const char *val)
 	system_set_dev_sysctl("/proc/sys/net/ipv6/conf/%s/disable_ipv6", dev->ifname, val);
 }
 
+static int system_get_sysctl(const char *path, char *buf, const size_t buf_sz)
+{
+	int fd = -1, ret = -1;
+
+	fd = open(path, O_RDONLY);
+	if (fd < 0)
+		goto out;
+
+	ssize_t len = read(fd, buf, buf_sz - 1);
+	if (len < 0)
+		goto out;
+
+	ret = buf[len] = 0;
+
+out:
+	if (fd >= 0)
+		close(fd);
+
+	return ret;
+}
+
+static int
+system_get_dev_sysctl(const char *path, const char *device, char *buf, const size_t buf_sz)
+{
+	snprintf(dev_buf, sizeof(dev_buf), path, device);
+	return system_get_sysctl(dev_buf, buf, buf_sz);
+}
+
+static int system_get_disable_ipv6(struct device *dev, char *buf, const size_t buf_sz)
+{
+	return system_get_dev_sysctl("/proc/sys/net/ipv6/conf/%s/disable_ipv6",
+			dev->ifname, buf, buf_sz);
+}
+
 #ifndef IFF_LOWER_UP
 #define IFF_LOWER_UP	0x10000
 #endif
@@ -380,7 +414,6 @@ int system_bridge_addif(struct device *bridge, struct device *dev)
 {
 	char *oldbr;
 
-	system_set_disable_ipv6(dev, "1");
 	oldbr = system_get_bridge(dev->ifname, dev_buf, sizeof(dev_buf));
 	if (oldbr && !strcmp(oldbr, bridge->ifname))
 		return 0;
@@ -390,7 +423,6 @@ int system_bridge_addif(struct device *bridge, struct device *dev)
 
 int system_bridge_delif(struct device *bridge, struct device *dev)
 {
-	system_set_disable_ipv6(dev, "0");
 	return system_bridge_if(bridge->ifname, dev, SIOCBRDELIF, NULL);
 }
 
@@ -777,6 +809,7 @@ static void
 system_if_get_settings(struct device *dev, struct device_settings *s)
 {
 	struct ifreq ifr;
+	char buf[10];
 
 	memset(&ifr, 0, sizeof(ifr));
 	strncpy(ifr.ifr_name, dev->ifname, sizeof(ifr.ifr_name));
@@ -795,6 +828,11 @@ system_if_get_settings(struct device *dev, struct device_settings *s)
 		memcpy(s->macaddr, &ifr.ifr_hwaddr.sa_data, sizeof(s->macaddr));
 		s->flags |= DEV_OPT_MACADDR;
 	}
+
+	if (!system_get_disable_ipv6(dev, buf, sizeof(buf))) {
+		s->ipv6 = !strtoul(buf, NULL, 0);
+		s->flags |= DEV_OPT_IPV6;
+	}
 }
 
 void
@@ -823,6 +861,8 @@ system_if_apply_settings(struct device *dev, struct device_settings *s, unsigned
 		if (ioctl(sock_ioctl, SIOCSIFHWADDR, &ifr) < 0)
 			s->flags &= ~DEV_OPT_MACADDR;
 	}
+	if (s->flags & DEV_OPT_IPV6 & apply_mask)
+		system_set_disable_ipv6(dev, s->ipv6 ? "0" : "1");
 }
 
 int system_if_up(struct device *dev)