Allow changing the MTU

2 files changed, 37 insertions, 12 deletions

diff --git a/fastd.c b/fastd.c
index 7373e86..1ce476f 100644
--- a/fastd.c
+++ b/fastd.c
@@ -60,11 +60,12 @@
 #include "fastd.h"
 
 
-#define FASTD_HEADROOM \
+#define FASTD_HDRLEN \
 	(ETH_HLEN + sizeof(struct ipv6hdr) + sizeof(struct udphdr) + 24)
 
 #define FASTD_DEFAULT_MTU 1500
 #define FASTD_MIN_MTU 68
+#define FASTD_MAX_MTU 65535
 
 
 static LIST_HEAD(fastd_list);
@@ -126,10 +127,23 @@ static struct notifier_block nl_notifier = {
 };
 
 
+
+static int fastd_ndo_change_mtu(struct net_device *dev, int mtu)
+{
+	if (mtu < FASTD_MIN_MTU || mtu > (FASTD_MAX_MTU-dev->hard_header_len))
+		return -EINVAL;
+
+	dev->mtu = mtu;
+	return 0;
+}
+
+
 static const struct net_device_ops fastd_netdev_ops_eth = {
+	.ndo_change_mtu		= fastd_ndo_change_mtu,
 };
 
 static const struct net_device_ops fastd_netdev_ops_ip = {
+	.ndo_change_mtu		= fastd_ndo_change_mtu,
 };
 
 
@@ -163,7 +177,8 @@ static const struct ethtool_ops fastd_ethtool_ops = {
 };
 
 
-static void fastd_netdev_free(struct net_device *dev) {
+static void fastd_netdev_free(struct net_device *dev)
+{
 	struct fastd_struct *fastd = netdev_priv(dev);
 
 	put_net(fastd->net);
@@ -178,6 +193,17 @@ static void fastd_netdev_setup(struct net_device *dev)
 	dev->destructor = fastd_netdev_free;
 }
 
+static inline u16 fastd_header_len(u16 mode)
+{
+	switch (mode) {
+	case FASTD_MODE_ETH:
+		return FASTD_HDRLEN + ETH_HLEN;
+
+	default:
+		return FASTD_HDRLEN;
+	}
+}
+
 static void fastd_netdev_init(struct net_device *dev)
 {
 	struct fastd_struct *fastd = netdev_priv(dev);
@@ -189,19 +215,17 @@ static void fastd_netdev_init(struct net_device *dev)
 		eth_hw_addr_random(dev);
 		ether_setup(dev);
 
-		dev->hard_header_len = FASTD_HEADROOM + ETH_HLEN;
-
 		break;
 
 	case FASTD_MODE_IP:
-		dev->netdev_ops = &fastd_netdev_ops_eth;
+		dev->netdev_ops = &fastd_netdev_ops_ip;
 
 		dev->addr_len = 0;
-		dev->hard_header_len = FASTD_HEADROOM;
-
 		dev->type = ARPHRD_NONE;
 		dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
 	}
+
+	dev->hard_header_len = fastd_header_len(fastd->mode);
 }
 
 static void fastd_destroy_work(struct work_struct *work)
@@ -240,10 +264,9 @@ static int fastd_cmd_create(struct sk_buff *skb, struct genl_info *info)
 	if (info->attrs[FASTD_A_MTU])
 		mtu = nla_get_u16(info->attrs[FASTD_A_MTU]);
 
-	if (mtu < FASTD_MIN_MTU)
+	if (mtu < FASTD_MIN_MTU || mtu > (FASTD_MAX_MTU-fastd_header_len(mode)))
 		return -EINVAL;
 
-
 	if (info->attrs[FASTD_A_IFNAME])
 		name = nla_data(info->attrs[FASTD_A_IFNAME]);
 
diff --git a/fastd.h b/fastd.h
index 5c3ca86..8b89130 100644
--- a/fastd.h
+++ b/fastd.h
@@ -39,9 +39,11 @@
 #ifndef __LINUX_FASTD_H
 #define __LINUX_FASTD_H
 
-#define FASTD_MODE_ETH	0x0001
-#define FASTD_MODE_IP	0x0002
-
+enum {
+	FASTD_MODE_UNSPEC,
+	FASTD_MODE_ETH,
+	FASTD_MODE_IP
+};
 
 enum {
 	FASTD_CMD_UNSPEC,