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![R. Parameswaran](/assets/img/avatar_default.png)
Existing L2TP kernel code does not derive the optimal MTU for Ethernet pseudowires and instead leaves this to a userspace L2TP daemon or operator. If an MTU is not specified, the existing kernel code chooses an MTU that does not take account of all tunnel header overheads, which can lead to unwanted IP fragmentation. When L2TP is used without a control plane (userspace daemon), we would prefer that the kernel does a better job of choosing a default pseudowire MTU, taking account of all tunnel header overheads, including IP header options, if any. This patch addresses this. Change-set here uses the new kernel function, kernel_sock_ip_overhead(), to factor the outer IP overhead on the L2TP tunnel socket (including IP Options, if any) when calculating the default MTU for an Ethernet pseudowire, along with consideration of the inner Ethernet header. Signed-off-by: R. Parameswaran <rparames@brocade.com> Signed-off-by: David S. Miller <davem@davemloft.net>
402 lines
9.5 KiB
C
402 lines
9.5 KiB
C
/*
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* L2TPv3 ethernet pseudowire driver
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*
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* Copyright (c) 2008,2009,2010 Katalix Systems Ltd
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/socket.h>
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#include <linux/hash.h>
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#include <linux/l2tp.h>
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#include <linux/in.h>
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#include <linux/etherdevice.h>
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#include <linux/spinlock.h>
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#include <net/sock.h>
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#include <net/ip.h>
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#include <net/icmp.h>
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#include <net/udp.h>
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#include <net/inet_common.h>
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#include <net/inet_hashtables.h>
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#include <net/tcp_states.h>
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#include <net/protocol.h>
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#include <net/xfrm.h>
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#include <net/net_namespace.h>
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#include <net/netns/generic.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/udp.h>
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#include "l2tp_core.h"
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/* Default device name. May be overridden by name specified by user */
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#define L2TP_ETH_DEV_NAME "l2tpeth%d"
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/* via netdev_priv() */
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struct l2tp_eth {
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struct net_device *dev;
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struct sock *tunnel_sock;
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struct l2tp_session *session;
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struct list_head list;
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atomic_long_t tx_bytes;
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atomic_long_t tx_packets;
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atomic_long_t tx_dropped;
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atomic_long_t rx_bytes;
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atomic_long_t rx_packets;
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atomic_long_t rx_errors;
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};
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/* via l2tp_session_priv() */
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struct l2tp_eth_sess {
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struct net_device *dev;
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};
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/* per-net private data for this module */
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static unsigned int l2tp_eth_net_id;
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struct l2tp_eth_net {
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struct list_head l2tp_eth_dev_list;
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spinlock_t l2tp_eth_lock;
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};
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static inline struct l2tp_eth_net *l2tp_eth_pernet(struct net *net)
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{
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return net_generic(net, l2tp_eth_net_id);
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}
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static int l2tp_eth_dev_init(struct net_device *dev)
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{
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struct l2tp_eth *priv = netdev_priv(dev);
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priv->dev = dev;
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eth_hw_addr_random(dev);
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eth_broadcast_addr(dev->broadcast);
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netdev_lockdep_set_classes(dev);
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return 0;
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}
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static void l2tp_eth_dev_uninit(struct net_device *dev)
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{
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struct l2tp_eth *priv = netdev_priv(dev);
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struct l2tp_eth_net *pn = l2tp_eth_pernet(dev_net(dev));
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spin_lock(&pn->l2tp_eth_lock);
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list_del_init(&priv->list);
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spin_unlock(&pn->l2tp_eth_lock);
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dev_put(dev);
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}
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static int l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
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{
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struct l2tp_eth *priv = netdev_priv(dev);
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struct l2tp_session *session = priv->session;
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unsigned int len = skb->len;
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int ret = l2tp_xmit_skb(session, skb, session->hdr_len);
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if (likely(ret == NET_XMIT_SUCCESS)) {
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atomic_long_add(len, &priv->tx_bytes);
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atomic_long_inc(&priv->tx_packets);
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} else {
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atomic_long_inc(&priv->tx_dropped);
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}
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return NETDEV_TX_OK;
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}
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static void l2tp_eth_get_stats64(struct net_device *dev,
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struct rtnl_link_stats64 *stats)
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{
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struct l2tp_eth *priv = netdev_priv(dev);
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stats->tx_bytes = atomic_long_read(&priv->tx_bytes);
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stats->tx_packets = atomic_long_read(&priv->tx_packets);
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stats->tx_dropped = atomic_long_read(&priv->tx_dropped);
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stats->rx_bytes = atomic_long_read(&priv->rx_bytes);
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stats->rx_packets = atomic_long_read(&priv->rx_packets);
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stats->rx_errors = atomic_long_read(&priv->rx_errors);
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}
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static const struct net_device_ops l2tp_eth_netdev_ops = {
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.ndo_init = l2tp_eth_dev_init,
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.ndo_uninit = l2tp_eth_dev_uninit,
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.ndo_start_xmit = l2tp_eth_dev_xmit,
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.ndo_get_stats64 = l2tp_eth_get_stats64,
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.ndo_set_mac_address = eth_mac_addr,
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};
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static void l2tp_eth_dev_setup(struct net_device *dev)
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{
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ether_setup(dev);
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dev->priv_flags &= ~IFF_TX_SKB_SHARING;
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dev->features |= NETIF_F_LLTX;
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dev->netdev_ops = &l2tp_eth_netdev_ops;
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dev->destructor = free_netdev;
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}
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static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
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{
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struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
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struct net_device *dev = spriv->dev;
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struct l2tp_eth *priv = netdev_priv(dev);
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if (session->debug & L2TP_MSG_DATA) {
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unsigned int length;
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length = min(32u, skb->len);
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if (!pskb_may_pull(skb, length))
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goto error;
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pr_debug("%s: eth recv\n", session->name);
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print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
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}
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if (!pskb_may_pull(skb, ETH_HLEN))
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goto error;
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secpath_reset(skb);
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/* checksums verified by L2TP */
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skb->ip_summed = CHECKSUM_NONE;
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skb_dst_drop(skb);
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nf_reset(skb);
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if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
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atomic_long_inc(&priv->rx_packets);
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atomic_long_add(data_len, &priv->rx_bytes);
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} else {
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atomic_long_inc(&priv->rx_errors);
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}
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return;
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error:
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atomic_long_inc(&priv->rx_errors);
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kfree_skb(skb);
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}
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static void l2tp_eth_delete(struct l2tp_session *session)
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{
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struct l2tp_eth_sess *spriv;
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struct net_device *dev;
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if (session) {
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spriv = l2tp_session_priv(session);
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dev = spriv->dev;
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if (dev) {
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unregister_netdev(dev);
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spriv->dev = NULL;
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module_put(THIS_MODULE);
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}
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}
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}
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#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
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static void l2tp_eth_show(struct seq_file *m, void *arg)
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{
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struct l2tp_session *session = arg;
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struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
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struct net_device *dev = spriv->dev;
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seq_printf(m, " interface %s\n", dev->name);
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}
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#endif
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static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
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struct l2tp_session *session,
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struct net_device *dev)
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{
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unsigned int overhead = 0;
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struct dst_entry *dst;
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u32 l3_overhead = 0;
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/* if the encap is UDP, account for UDP header size */
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if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
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overhead += sizeof(struct udphdr);
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dev->needed_headroom += sizeof(struct udphdr);
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}
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if (session->mtu != 0) {
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dev->mtu = session->mtu;
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dev->needed_headroom += session->hdr_len;
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return;
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}
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l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
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if (l3_overhead == 0) {
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/* L3 Overhead couldn't be identified, this could be
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* because tunnel->sock was NULL or the socket's
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* address family was not IPv4 or IPv6,
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* dev mtu stays at 1500.
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*/
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return;
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}
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/* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
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* UDP overhead, if any, was already factored in above.
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*/
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overhead += session->hdr_len + ETH_HLEN + l3_overhead;
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/* If PMTU discovery was enabled, use discovered MTU on L2TP device */
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dst = sk_dst_get(tunnel->sock);
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if (dst) {
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/* dst_mtu will use PMTU if found, else fallback to intf MTU */
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u32 pmtu = dst_mtu(dst);
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if (pmtu != 0)
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dev->mtu = pmtu;
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dst_release(dst);
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}
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session->mtu = dev->mtu - overhead;
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dev->mtu = session->mtu;
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dev->needed_headroom += session->hdr_len;
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}
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static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
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{
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struct net_device *dev;
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char name[IFNAMSIZ];
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struct l2tp_tunnel *tunnel;
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struct l2tp_session *session;
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struct l2tp_eth *priv;
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struct l2tp_eth_sess *spriv;
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int rc;
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struct l2tp_eth_net *pn;
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tunnel = l2tp_tunnel_find(net, tunnel_id);
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if (!tunnel) {
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rc = -ENODEV;
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goto out;
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}
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if (cfg->ifname) {
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dev = dev_get_by_name(net, cfg->ifname);
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if (dev) {
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dev_put(dev);
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rc = -EEXIST;
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goto out;
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}
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strlcpy(name, cfg->ifname, IFNAMSIZ);
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} else
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strcpy(name, L2TP_ETH_DEV_NAME);
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session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
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peer_session_id, cfg);
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if (IS_ERR(session)) {
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rc = PTR_ERR(session);
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goto out;
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}
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dev = alloc_netdev(sizeof(*priv), name, NET_NAME_UNKNOWN,
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l2tp_eth_dev_setup);
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if (!dev) {
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rc = -ENOMEM;
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goto out_del_session;
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}
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dev_net_set(dev, net);
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dev->min_mtu = 0;
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dev->max_mtu = ETH_MAX_MTU;
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l2tp_eth_adjust_mtu(tunnel, session, dev);
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priv = netdev_priv(dev);
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priv->dev = dev;
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priv->session = session;
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INIT_LIST_HEAD(&priv->list);
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priv->tunnel_sock = tunnel->sock;
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session->recv_skb = l2tp_eth_dev_recv;
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session->session_close = l2tp_eth_delete;
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#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
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session->show = l2tp_eth_show;
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#endif
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spriv = l2tp_session_priv(session);
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spriv->dev = dev;
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rc = register_netdev(dev);
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if (rc < 0)
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goto out_del_dev;
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__module_get(THIS_MODULE);
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/* Must be done after register_netdev() */
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strlcpy(session->ifname, dev->name, IFNAMSIZ);
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dev_hold(dev);
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pn = l2tp_eth_pernet(dev_net(dev));
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spin_lock(&pn->l2tp_eth_lock);
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list_add(&priv->list, &pn->l2tp_eth_dev_list);
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spin_unlock(&pn->l2tp_eth_lock);
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return 0;
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out_del_dev:
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free_netdev(dev);
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spriv->dev = NULL;
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out_del_session:
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l2tp_session_delete(session);
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out:
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return rc;
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}
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static __net_init int l2tp_eth_init_net(struct net *net)
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{
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struct l2tp_eth_net *pn = net_generic(net, l2tp_eth_net_id);
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INIT_LIST_HEAD(&pn->l2tp_eth_dev_list);
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spin_lock_init(&pn->l2tp_eth_lock);
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return 0;
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}
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static struct pernet_operations l2tp_eth_net_ops = {
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.init = l2tp_eth_init_net,
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.id = &l2tp_eth_net_id,
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.size = sizeof(struct l2tp_eth_net),
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};
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static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
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.session_create = l2tp_eth_create,
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.session_delete = l2tp_session_delete,
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};
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static int __init l2tp_eth_init(void)
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{
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int err = 0;
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err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
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if (err)
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goto out;
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err = register_pernet_device(&l2tp_eth_net_ops);
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if (err)
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goto out_unreg;
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pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
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return 0;
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out_unreg:
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l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
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out:
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return err;
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}
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static void __exit l2tp_eth_exit(void)
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{
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unregister_pernet_device(&l2tp_eth_net_ops);
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l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
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}
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module_init(l2tp_eth_init);
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module_exit(l2tp_eth_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
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MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
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MODULE_VERSION("1.0");
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MODULE_ALIAS_L2TP_PWTYPE(5);
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