Add mtu6 option to override IPv6 MTU

Signed-off-by: Steven Barth <steven@midlink.org>

5 files changed, 35 insertions, 16 deletions

diff --git a/bridge.c b/bridge.c
index 9da5314..4a0cbe9 100644
--- a/bridge.c
+++ b/bridge.c
@@ -299,7 +299,7 @@ bridge_member_cb(struct device_user *dev, enum device_event ev)
 			 * bridge mtu is set
 			 */
 			system_if_apply_settings(&bst->dev, &bst->dev.settings,
-						 DEV_OPT_MTU);
+						 DEV_OPT_MTU | DEV_OPT_MTU6);
 		}
 
 		break;
diff --git a/device.c b/device.c
index dd2823d..1265c86 100644
--- a/device.c
+++ b/device.c
@@ -34,6 +34,7 @@ static bool default_ps = true;
 static const struct blobmsg_policy dev_attrs[__DEV_ATTR_MAX] = {
 	[DEV_ATTR_TYPE] = { .name = "type", .type = BLOBMSG_TYPE_STRING },
 	[DEV_ATTR_MTU] = { .name = "mtu", .type = BLOBMSG_TYPE_INT32 },
+	[DEV_ATTR_MTU6] = { .name = "mtu6", .type = BLOBMSG_TYPE_INT32 },
 	[DEV_ATTR_MACADDR] = { .name = "macaddr", .type = BLOBMSG_TYPE_STRING },
 	[DEV_ATTR_TXQUEUELEN] = { .name = "txqueuelen", .type = BLOBMSG_TYPE_INT32 },
 	[DEV_ATTR_ENABLED] = { .name = "enabled", .type = BLOBMSG_TYPE_BOOL },
@@ -154,6 +155,7 @@ device_merge_settings(struct device *dev, struct device_settings *n)
 
 	memset(n, 0, sizeof(*n));
 	n->mtu = s->flags & DEV_OPT_MTU ? s->mtu : os->mtu;
+	n->mtu6 = s->flags & DEV_OPT_MTU6 ? s->mtu6 : os->mtu6;
 	n->txqueuelen = s->flags & DEV_OPT_TXQUEUELEN ?
 		s->txqueuelen : os->txqueuelen;
 	memcpy(n->macaddr,
@@ -189,6 +191,11 @@ device_init_settings(struct device *dev, struct blob_attr **tb)
 		s->flags |= DEV_OPT_MTU;
 	}
 
+	if ((cur = tb[DEV_ATTR_MTU6])) {
+		s->mtu6 = blobmsg_get_u32(cur);
+		s->flags |= DEV_OPT_MTU6;
+	}
+
 	if ((cur = tb[DEV_ATTR_TXQUEUELEN])) {
 		s->txqueuelen = blobmsg_get_u32(cur);
 		s->flags |= DEV_OPT_TXQUEUELEN;
@@ -843,6 +850,8 @@ device_dump_status(struct blob_buf *b, struct device *dev)
 		device_merge_settings(dev, &st);
 		if (st.flags & DEV_OPT_MTU)
 			blobmsg_add_u32(b, "mtu", st.mtu);
+		if (st.flags & DEV_OPT_MTU6)
+			blobmsg_add_u32(b, "mtu6", st.mtu6);
 		if (st.flags & DEV_OPT_MACADDR)
 			blobmsg_add_string(b, "macaddr", format_macaddr(st.macaddr));
 		if (st.flags & DEV_OPT_TXQUEUELEN)
diff --git a/device.h b/device.h
index 3001f10..4d84d80 100644
--- a/device.h
+++ b/device.h
@@ -28,6 +28,7 @@ typedef int (*device_state_cb)(struct device *, bool up);
 enum {
 	DEV_ATTR_TYPE,
 	DEV_ATTR_MTU,
+	DEV_ATTR_MTU6,
 	DEV_ATTR_MACADDR,
 	DEV_ATTR_TXQUEUELEN,
 	DEV_ATTR_ENABLED,
@@ -80,6 +81,7 @@ enum {
 	DEV_OPT_NEIGHREACHABLETIME	= (1 << 9),
 	DEV_OPT_RPS			= (1 << 10),
 	DEV_OPT_XPS			= (1 << 11),
+	DEV_OPT_MTU6		= (1 << 12),
 };
 
 /* events broadcasted to all users of a device */
@@ -123,6 +125,7 @@ struct device_user {
 struct device_settings {
 	unsigned int flags;
 	unsigned int mtu;
+	unsigned int mtu6;
 	unsigned int txqueuelen;
 	uint8_t macaddr[6];
 	bool ipv6;
diff --git a/interface-ip.c b/interface-ip.c
index aec3892..7f8a451 100644
--- a/interface-ip.c
+++ b/interface-ip.c
@@ -767,10 +767,11 @@ interface_set_prefix_address(struct device_prefix_assignment *assignment,
 		route.metric = iface->metric;
 		system_add_route(l3_downlink, &route);
 
-		if (uplink && uplink->l3_dev.dev) {
-			int mtu = system_update_ipv6_mtu(
-					uplink->l3_dev.dev, 0);
-			if (mtu > 0)
+		if (uplink && uplink->l3_dev.dev && !(l3_downlink->settings.flags & DEV_OPT_MTU6)) {
+			int mtu = system_update_ipv6_mtu(uplink->l3_dev.dev, 0);
+			int mtu_old = system_update_ipv6_mtu(l3_downlink, 0);
+
+			if (mtu > 0 && mtu_old > mtu)
 				system_update_ipv6_mtu(l3_downlink, mtu);
 		}
 
diff --git a/system-linux.c b/system-linux.c
index 6dc9acd..b44eb76 100644
--- a/system-linux.c
+++ b/system-linux.c
@@ -1019,6 +1019,10 @@ system_if_get_settings(struct device *dev, struct device_settings *s)
 		s->flags |= DEV_OPT_MTU;
 	}
 
+	s->mtu6 = system_update_ipv6_mtu(dev, 0);
+	if (s->mtu6 > 0)
+		s->flags |= DEV_OPT_MTU6;
+
 	if (ioctl(sock_ioctl, SIOCGIFTXQLEN, &ifr) == 0) {
 		s->txqueuelen = ifr.ifr_qlen;
 		s->flags |= DEV_OPT_TXQUEUELEN;
@@ -1114,6 +1118,9 @@ system_if_apply_settings(struct device *dev, struct device_settings *s, unsigned
 		if (ioctl(sock_ioctl, SIOCSIFMTU, &ifr) < 0)
 			s->flags &= ~DEV_OPT_MTU;
 	}
+	if (s->flags & DEV_OPT_MTU6 & apply_mask) {
+		system_update_ipv6_mtu(dev, s->mtu6);
+	}
 	if (s->flags & DEV_OPT_TXQUEUELEN & apply_mask) {
 		ifr.ifr_qlen = s->txqueuelen;
 		if (ioctl(sock_ioctl, SIOCSIFTXQLEN, &ifr) < 0)
@@ -2163,19 +2170,18 @@ int system_update_ipv6_mtu(struct device *dev, int mtu)
 			dev->ifname);
 
 	int fd = open(buf, O_RDWR);
-	ssize_t len = read(fd, buf, sizeof(buf) - 1);
-	if (len < 0)
-		goto out;
 
-	buf[len] = 0;
-	ret = atoi(buf);
+	if (!mtu) {
+		ssize_t len = read(fd, buf, sizeof(buf) - 1);
+		if (len < 0)
+			goto out;
 
-	if (!mtu || ret <= mtu)
-		goto out;
-
-	lseek(fd, 0, SEEK_SET);
-	if (write(fd, buf, snprintf(buf, sizeof(buf), "%i", mtu)) <= 0)
-		ret = -1;
+		buf[len] = 0;
+		ret = atoi(buf);
+	} else {
+		if (write(fd, buf, snprintf(buf, sizeof(buf), "%i", mtu)) > 0)
+			ret = mtu;
+	}
 
 out:
 	close(fd);