Merge branch 'geneve-mtu'

Alexey Kodanev says:

====================
geneve: verify user specified MTU or adjust with a lower device

The first two patches don't introduce any functional changes and
contain minor cleanups for code readability.

The last one adds a new function geneve_link_config() similar to the
other tunnels. The function will be used on a new link creation or
when 'remote' parameter is changed. It adjusts a user specified MTU
or, if it finds a lower device, tunes the tunnel MTU using it.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/geneve.c

@@ -36,6 +36,8 @@ MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN");
 
 #define GENEVE_VER 0
 #define GENEVE_BASE_HLEN (sizeof(struct udphdr) + sizeof(struct genevehdr))
+#define GENEVE_IPV4_HLEN (ETH_HLEN + sizeof(struct iphdr) + GENEVE_BASE_HLEN)
+#define GENEVE_IPV6_HLEN (ETH_HLEN + sizeof(struct ipv6hdr) + GENEVE_BASE_HLEN)
 
 /* per-network namespace private data for this module */
 struct geneve_net {
@@ -826,8 +828,8 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 		return PTR_ERR(rt);
 
 	if (skb_dst(skb)) {
-		int mtu = dst_mtu(&rt->dst) - sizeof(struct iphdr) -
-			  GENEVE_BASE_HLEN - info->options_len - 14;
+		int mtu = dst_mtu(&rt->dst) - GENEVE_IPV4_HLEN -
+			  info->options_len;
 
 		skb_dst_update_pmtu(skb, mtu);
 	}
@@ -872,8 +874,7 @@ static int geneve6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 		return PTR_ERR(dst);
 
 	if (skb_dst(skb)) {
-		int mtu = dst_mtu(dst) - sizeof(struct ipv6hdr) -
-			  GENEVE_BASE_HLEN - info->options_len - 14;
+		int mtu = dst_mtu(dst) - GENEVE_IPV6_HLEN - info->options_len;
 
 		skb_dst_update_pmtu(skb, mtu);
 	}
@@ -941,11 +942,10 @@ static netdev_tx_t geneve_xmit(struct sk_buff *skb, struct net_device *dev)
 
 static int geneve_change_mtu(struct net_device *dev, int new_mtu)
 {
-	/* Only possible if called internally, ndo_change_mtu path's new_mtu
-	 * is guaranteed to be between dev->min_mtu and dev->max_mtu.
-	 */
 	if (new_mtu > dev->max_mtu)
 		new_mtu = dev->max_mtu;
+	else if (new_mtu < dev->min_mtu)
+		new_mtu = dev->min_mtu;
 
 	dev->mtu = new_mtu;
 	return 0;
@@ -1261,7 +1261,7 @@ static int geneve_nl2info(struct nlattr *tb[], struct nlattr *data[],
 	}
 
 	if (data[IFLA_GENEVE_REMOTE6]) {
- #if IS_ENABLED(CONFIG_IPV6)
+#if IS_ENABLED(CONFIG_IPV6)
 		if (changelink && (ip_tunnel_info_af(info) == AF_INET)) {
 			attrtype = IFLA_GENEVE_REMOTE6;
 			goto change_notsup;
@@ -1387,6 +1387,48 @@ static int geneve_nl2info(struct nlattr *tb[], struct nlattr *data[],
 	return -EOPNOTSUPP;
 }
 
+static void geneve_link_config(struct net_device *dev,
+			       struct ip_tunnel_info *info, struct nlattr *tb[])
+{
+	struct geneve_dev *geneve = netdev_priv(dev);
+	int ldev_mtu = 0;
+
+	if (tb[IFLA_MTU]) {
+		geneve_change_mtu(dev, nla_get_u32(tb[IFLA_MTU]));
+		return;
+	}
+
+	switch (ip_tunnel_info_af(info)) {
+	case AF_INET: {
+		struct flowi4 fl4 = { .daddr = info->key.u.ipv4.dst };
+		struct rtable *rt = ip_route_output_key(geneve->net, &fl4);
+
+		if (!IS_ERR(rt) && rt->dst.dev) {
+			ldev_mtu = rt->dst.dev->mtu - GENEVE_IPV4_HLEN;
+			ip_rt_put(rt);
+		}
+		break;
+	}
+#if IS_ENABLED(CONFIG_IPV6)
+	case AF_INET6: {
+		struct rt6_info *rt = rt6_lookup(geneve->net,
+						 &info->key.u.ipv6.dst, NULL, 0,
+						 NULL, 0);
+
+		if (rt && rt->dst.dev)
+			ldev_mtu = rt->dst.dev->mtu - GENEVE_IPV6_HLEN;
+		ip6_rt_put(rt);
+		break;
+	}
+#endif
+	}
+
+	if (ldev_mtu <= 0)
+		return;
+
+	geneve_change_mtu(dev, ldev_mtu - info->options_len);
+}
+
 static int geneve_newlink(struct net *net, struct net_device *dev,
 			  struct nlattr *tb[], struct nlattr *data[],
 			  struct netlink_ext_ack *extack)
@@ -1402,8 +1444,14 @@ static int geneve_newlink(struct net *net, struct net_device *dev,
 	if (err)
 		return err;
 
-	return geneve_configure(net, dev, extack, &info, metadata,
+	err = geneve_configure(net, dev, extack, &info, metadata,
 			       use_udp6_rx_checksums);
+	if (err)
+		return err;
+
+	geneve_link_config(dev, &info, tb);
+
+	return 0;
 }
 
 /* Quiesces the geneve device data path for both TX and RX.
@@ -1477,8 +1525,10 @@ static int geneve_changelink(struct net_device *dev, struct nlattr *tb[],
 	if (err)
 		return err;
 
-	if (!geneve_dst_addr_equal(&geneve->info, &info))
+	if (!geneve_dst_addr_equal(&geneve->info, &info)) {
 		dst_cache_reset(&info.dst_cache);
+		geneve_link_config(dev, &info, tb);
+	}
 
 	geneve_quiesce(geneve, &gs4, &gs6);
 	geneve->info = info;