cregit-Linux how code gets into the kernel

Release 4.11 net/ipv4/ip_tunnel.c

Directory: net/ipv4
/*
 * Copyright (c) 2013 Nicira, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA
 */


#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/capability.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/in.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/if_arp.h>
#include <linux/init.h>
#include <linux/in6.h>
#include <linux/inetdevice.h>
#include <linux/igmp.h>
#include <linux/netfilter_ipv4.h>
#include <linux/etherdevice.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/rculist.h>
#include <linux/err.h>

#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/protocol.h>
#include <net/ip_tunnels.h>
#include <net/arp.h>
#include <net/checksum.h>
#include <net/dsfield.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/rtnetlink.h>
#include <net/udp.h>
#include <net/dst_metadata.h>

#if IS_ENABLED(CONFIG_IPV6)
#include <net/ipv6.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#endif




static unsigned int ip_tunnel_hash(__be32 key, __be32 remote)
{
	return hash_32((__force u32)key ^ (__force u32)remote,
			 IP_TNL_HASH_BITS);
}


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static bool ip_tunnel_key_match(const struct ip_tunnel_parm *p,
				__be16 flags, __be32 key)
{
	if (p->i_flags & TUNNEL_KEY) {
		if (flags & TUNNEL_KEY)
			return key == p->i_key;
		else
			/* key expected, none present */
			return false;
	} else
		return !(flags & TUNNEL_KEY);
}


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/* Fallback tunnel: no source, no destination, no key, no options

   Tunnel hash table:
   We require exact key match i.e. if a key is present in packet
   it will match only tunnel with the same key; if it is not present,
   it will match only keyless tunnel.

   All keysless packets, if not matched configured keyless tunnels
   will match fallback tunnel.
   Given src, dst and key, find appropriate for input tunnel.
*/



struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
				   int link, __be16 flags,
				   __be32 remote, __be32 local,
				   __be32 key)
{
	unsigned int hash;
	struct ip_tunnel *t, *cand = NULL;
	struct hlist_head *head;

	hash = ip_tunnel_hash(key, remote);
	head = &itn->tunnels[hash];

	hlist_for_each_entry_rcu(t, head, hash_node) {
		if (local != t->parms.iph.saddr ||
		    remote != t->parms.iph.daddr ||
		    !(t->dev->flags & IFF_UP))
			continue;

		if (!ip_tunnel_key_match(&t->parms, flags, key))
			continue;

		if (t->parms.link == link)
			return t;
		else
			cand = t;
	}

	hlist_for_each_entry_rcu(t, head, hash_node) {
		if (remote != t->parms.iph.daddr ||
		    t->parms.iph.saddr != 0 ||
		    !(t->dev->flags & IFF_UP))
			continue;

		if (!ip_tunnel_key_match(&t->parms, flags, key))
			continue;

		if (t->parms.link == link)
			return t;
		else if (!cand)
			cand = t;
	}

	hash = ip_tunnel_hash(key, 0);
	head = &itn->tunnels[hash];

	hlist_for_each_entry_rcu(t, head, hash_node) {
		if ((local != t->parms.iph.saddr || t->parms.iph.daddr != 0) &&
		    (local != t->parms.iph.daddr || !ipv4_is_multicast(local)))
			continue;

		if (!(t->dev->flags & IFF_UP))
			continue;

		if (!ip_tunnel_key_match(&t->parms, flags, key))
			continue;

		if (t->parms.link == link)
			return t;
		else if (!cand)
			cand = t;
	}

	if (flags & TUNNEL_NO_KEY)
		goto skip_key_lookup;

	hlist_for_each_entry_rcu(t, head, hash_node) {
		if (t->parms.i_key != key ||
		    t->parms.iph.saddr != 0 ||
		    t->parms.iph.daddr != 0 ||
		    !(t->dev->flags & IFF_UP))
			continue;

		if (t->parms.link == link)
			return t;
		else if (!cand)
			cand = t;
	}

skip_key_lookup:
	if (cand)
		return cand;

	t = rcu_dereference(itn->collect_md_tun);
	if (t)
		return t;

	if (itn->fb_tunnel_dev && itn->fb_tunnel_dev->flags & IFF_UP)
		return netdev_priv(itn->fb_tunnel_dev);

	return NULL;
}

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EXPORT_SYMBOL_GPL(ip_tunnel_lookup);




static struct hlist_head *ip_bucket(struct ip_tunnel_net *itn,
				    struct ip_tunnel_parm *parms)
{
	unsigned int h;
	__be32 remote;
	__be32 i_key = parms->i_key;

	if (parms->iph.daddr && !ipv4_is_multicast(parms->iph.daddr))
		remote = parms->iph.daddr;
	else
		remote = 0;

	if (!(parms->i_flags & TUNNEL_KEY) && (parms->i_flags & VTI_ISVTI))
		i_key = 0;

	h = ip_tunnel_hash(i_key, remote);
	return &itn->tunnels[h];
}


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static void ip_tunnel_add(struct ip_tunnel_net *itn, struct ip_tunnel *t)
{
	struct hlist_head *head = ip_bucket(itn, &t->parms);

	if (t->collect_md)
		rcu_assign_pointer(itn->collect_md_tun, t);
	hlist_add_head_rcu(&t->hash_node, head);
}


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static void ip_tunnel_del(struct ip_tunnel_net *itn, struct ip_tunnel *t)
{
	if (t->collect_md)
		rcu_assign_pointer(itn->collect_md_tun, NULL);
	hlist_del_init_rcu(&t->hash_node);
}


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static struct ip_tunnel *ip_tunnel_find(struct ip_tunnel_net *itn,
					struct ip_tunnel_parm *parms,
					int type)
{
	__be32 remote = parms->iph.daddr;
	__be32 local = parms->iph.saddr;
	__be32 key = parms->i_key;
	__be16 flags = parms->i_flags;
	int link = parms->link;
	struct ip_tunnel *t = NULL;
	struct hlist_head *head = ip_bucket(itn, parms);

	hlist_for_each_entry_rcu(t, head, hash_node) {
		if (local == t->parms.iph.saddr &&
		    remote == t->parms.iph.daddr &&
		    link == t->parms.link &&
		    type == t->dev->type &&
		    ip_tunnel_key_match(&t->parms, flags, key))
			break;
	}
	return t;
}


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static struct net_device *__ip_tunnel_create(struct net *net,
					     const struct rtnl_link_ops *ops,
					     struct ip_tunnel_parm *parms)
{
	int err;
	struct ip_tunnel *tunnel;
	struct net_device *dev;
	char name[IFNAMSIZ];

	if (parms->name[0])
		strlcpy(name, parms->name, IFNAMSIZ);
	else {
		if (strlen(ops->kind) > (IFNAMSIZ - 3)) {
			err = -E2BIG;
			goto failed;
		}
		strlcpy(name, ops->kind, IFNAMSIZ);
		strncat(name, "%d", 2);
	}

	ASSERT_RTNL();
	dev = alloc_netdev(ops->priv_size, name, NET_NAME_UNKNOWN, ops->setup);
	if (!dev) {
		err = -ENOMEM;
		goto failed;
	}
	dev_net_set(dev, net);

	dev->rtnl_link_ops = ops;

	tunnel = netdev_priv(dev);
	tunnel->parms = *parms;
	tunnel->net = net;

	err = register_netdevice(dev);
	if (err)
		goto failed_free;

	return dev;

failed_free:
	free_netdev(dev);
failed:
	return ERR_PTR(err);
}


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static inline void init_tunnel_flow(struct flowi4 *fl4,
				    int proto,
				    __be32 daddr, __be32 saddr,
				    __be32 key, __u8 tos, int oif)
{
	memset(fl4, 0, sizeof(*fl4));
	fl4->flowi4_oif = oif;
	fl4->daddr = daddr;
	fl4->saddr = saddr;
	fl4->flowi4_tos = tos;
	fl4->flowi4_proto = proto;
	fl4->fl4_gre_key = key;
}


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static int ip_tunnel_bind_dev(struct net_device *dev)
{
	struct net_device *tdev = NULL;
	struct ip_tunnel *tunnel = netdev_priv(dev);
	const struct iphdr *iph;
	int hlen = LL_MAX_HEADER;
	int mtu = ETH_DATA_LEN;
	int t_hlen = tunnel->hlen + sizeof(struct iphdr);

	iph = &tunnel->parms.iph;

	/* Guess output device to choose reasonable mtu and needed_headroom */
	if (iph->daddr) {
		struct flowi4 fl4;
		struct rtable *rt;

		init_tunnel_flow(&fl4, iph->protocol, iph->daddr,
				 iph->saddr, tunnel->parms.o_key,
				 RT_TOS(iph->tos), tunnel->parms.link);
		rt = ip_route_output_key(tunnel->net, &fl4);

		if (!IS_ERR(rt)) {
			tdev = rt->dst.dev;
			ip_rt_put(rt);
		}
		if (dev->type != ARPHRD_ETHER)
			dev->flags |= IFF_POINTOPOINT;

		dst_cache_reset(&tunnel->dst_cache);
	}

	if (!tdev && tunnel->parms.link)
		tdev = __dev_get_by_index(tunnel->net, tunnel->parms.link);

	if (tdev) {
		hlen = tdev->hard_header_len + tdev->needed_headroom;
		mtu = tdev->mtu;
	}

	dev->needed_headroom = t_hlen + hlen;
	mtu -= (dev->hard_header_len + t_hlen);

	if (mtu < 68)
		mtu = 68;

	return mtu;
}


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static struct ip_tunnel *ip_tunnel_create(struct net *net,
					  struct ip_tunnel_net *itn,
					  struct ip_tunnel_parm *parms)
{
	struct ip_tunnel *nt;
	struct net_device *dev;
	int t_hlen;

	BUG_ON(!itn->fb_tunnel_dev);
	dev = __ip_tunnel_create(net, itn->fb_tunnel_dev->rtnl_link_ops, parms);
	if (IS_ERR(dev))
		return ERR_CAST(dev);

	dev->mtu = ip_tunnel_bind_dev(dev);

	nt = netdev_priv(dev);
	t_hlen = nt->hlen + sizeof(struct iphdr);
	dev->min_mtu = ETH_MIN_MTU;
	dev->max_mtu = 0xFFF8 - dev->hard_header_len - t_hlen;
	ip_tunnel_add(itn, nt);
	return nt;
}


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int ip_tunnel_rcv(struct ip_tunnel *tunnel, struct sk_buff *skb,
		  const struct tnl_ptk_info *tpi, struct metadata_dst *tun_dst,
		  bool log_ecn_error)
{
	struct pcpu_sw_netstats *tstats;
	const struct iphdr *iph = ip_hdr(skb);
	int err;

#ifdef CONFIG_NET_IPGRE_BROADCAST
	if (ipv4_is_multicast(iph->daddr)) {
		tunnel->dev->stats.multicast++;
		skb->pkt_type = PACKET_BROADCAST;
	}
#endif

	if ((!(tpi->flags&TUNNEL_CSUM) &&  (tunnel->parms.i_flags&TUNNEL_CSUM)) ||
	     ((tpi->flags&TUNNEL_CSUM) && !(tunnel->parms.i_flags&TUNNEL_CSUM))) {
		tunnel->dev->stats.rx_crc_errors++;
		tunnel->dev->stats.rx_errors++;
		goto drop;
	}

	if (tunnel->parms.i_flags&TUNNEL_SEQ) {
		if (!(tpi->flags&TUNNEL_SEQ) ||
		    (tunnel->i_seqno && (s32)(ntohl(tpi->seq) - tunnel->i_seqno) < 0)) {
			tunnel->dev->stats.rx_fifo_errors++;
			tunnel->dev->stats.rx_errors++;
			goto drop;
		}
		tunnel->i_seqno = ntohl(tpi->seq) + 1;
	}

	skb_reset_network_header(skb);

	err = IP_ECN_decapsulate(iph, skb);
	if (unlikely(err)) {
		if (log_ecn_error)
			net_info_ratelimited("non-ECT from %pI4 with TOS=%#x\n",
					&iph->saddr, iph->tos);
		if (err > 1) {
			++tunnel->dev->stats.rx_frame_errors;
			++tunnel->dev->stats.rx_errors;
			goto drop;
		}
	}

	tstats = this_cpu_ptr(tunnel->dev->tstats);
	u64_stats_update_begin(&tstats->syncp);
	tstats->rx_packets++;
	tstats->rx_bytes += skb->len;
	u64_stats_update_end(&tstats->syncp);

	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(tunnel->dev)));

	if (tunnel->dev->type == ARPHRD_ETHER) {
		skb->protocol = eth_type_trans(skb, tunnel->dev);
		skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
	} else {
		skb->dev = tunnel->dev;
	}

	if (tun_dst)
		skb_dst_set(skb, (struct dst_entry *)tun_dst);

	gro_cells_receive(&tunnel->gro_cells, skb);
	return 0;

drop:
	kfree_skb(skb);
	return 0;
}

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EXPORT_SYMBOL_GPL(ip_tunnel_rcv);




int ip_tunnel_encap_add_ops(const struct ip_tunnel_encap_ops *ops,
			    unsigned int num)
{
	if (num >= MAX_IPTUN_ENCAP_OPS)
		return -ERANGE;

	return !cmpxchg((const struct ip_tunnel_encap_ops **)
			&iptun_encaps[num],
			NULL, ops) ? 0 : -1;
}

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EXPORT_SYMBOL(ip_tunnel_encap_add_ops);




int ip_tunnel_encap_del_ops(const struct ip_tunnel_encap_ops *ops,
			    unsigned int num)
{
	int ret;

	if (num >= MAX_IPTUN_ENCAP_OPS)
		return -ERANGE;

	ret = (cmpxchg((const struct ip_tunnel_encap_ops **)
		       &iptun_encaps[num],
		       ops, NULL) == ops) ? 0 : -1;

	synchronize_net();

	return ret;
}

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EXPORT_SYMBOL(ip_tunnel_encap_del_ops);




int ip_tunnel_encap_setup(struct ip_tunnel *t,
			  struct ip_tunnel_encap *ipencap)
{
	int hlen;

	memset(&t->encap, 0, sizeof(t->encap));

	hlen = ip_encap_hlen(ipencap);
	if (hlen < 0)
		return hlen;

	t->encap.type = ipencap->type;
	t->encap.sport = ipencap->sport;
	t->encap.dport = ipencap->dport;
	t->encap.flags = ipencap->flags;

	t->encap_hlen = hlen;
	t->hlen = t->encap_hlen + t->tun_hlen;

	return 0;
}

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EXPORT_SYMBOL_GPL(ip_tunnel_encap_setup);




static int tnl_update_pmtu(struct net_device *dev, struct sk_buff *skb,
			    struct rtable *rt, __be16 df,
			    const struct iphdr *inner_iph)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	int pkt_size = skb->len - tunnel->hlen - dev->hard_header_len;
	int mtu;

	if (df)
		mtu = dst_mtu(&rt->dst) - dev->hard_header_len
					- sizeof(struct iphdr) - tunnel->hlen;
	else
		mtu = skb_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;

	if (skb_dst(skb))
		skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);

	if (skb->protocol == htons(ETH_P_IP)) {
		if (!skb_is_gso(skb) &&
		    (inner_iph->frag_off & htons(IP_DF)) &&
		    mtu < pkt_size) {
			memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
			return -E2BIG;
		}
	}
#if IS_ENABLED(CONFIG_IPV6)
	else if (skb->protocol == htons(ETH_P_IPV6)) {
		struct rt6_info *rt6 = (struct rt6_info *)skb_dst(skb);

		if (rt6 && mtu < dst_mtu(skb_dst(skb)) &&
			   mtu >= IPV6_MIN_MTU) {
			if ((tunnel->parms.iph.daddr &&
			    !ipv4_is_multicast(tunnel->parms.iph.daddr)) ||
			    rt6->rt6i_dst.plen == 128) {
				rt6->rt6i_flags |= RTF_MODIFIED;
				dst_metric_set(skb_dst(skb), RTAX_MTU, mtu);
			}
		}

		if (!skb_is_gso(skb) && mtu >= IPV6_MIN_MTU &&
					mtu < pkt_size) {
			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
			return -E2BIG;
		}
	}
#endif
	return 0;
}


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void ip_md_tunnel_xmit(struct sk_buff *skb, struct net_device *dev, u8 proto)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	u32 headroom = sizeof(struct iphdr);
	struct ip_tunnel_info *tun_info;
	const struct ip_tunnel_key *key;
	const struct iphdr *inner_iph;
	struct rtable *rt;
	struct flowi4 fl4;
	__be16 df = 0;
	u8 tos, ttl;

	tun_info = skb_tunnel_info(skb);
	if (unlikely(!tun_info || !(tun_info->mode & IP_TUNNEL_INFO_TX) ||
		     ip_tunnel_info_af(tun_info) != AF_INET))
		goto tx_error;
	key = &tun_info->key;
	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
	inner_iph = (const struct iphdr *)skb_inner_network_header(skb);
	tos = key->tos;
	if (tos == 1) {
		if (skb->protocol == htons(ETH_P_IP))
			tos = inner_iph->tos;
		else if (skb->protocol == htons(ETH_P_IPV6))
			tos = ipv6_get_dsfield((const struct ipv6hdr *)inner_iph);
	}
	init_tunnel_flow(&fl4, proto, key->u.ipv4.dst, key->u.ipv4.src, 0,
			 RT_TOS(tos), tunnel->parms.link);
	if (tunnel->encap.type != TUNNEL_ENCAP_NONE)
		goto tx_error;
	rt = ip_route_output_key(tunnel->net, &fl4);
	if (IS_ERR(rt)) {
		dev->stats.tx_carrier_errors++;
		goto tx_error;
	}
	if (rt->dst.dev == dev) {
		ip_rt_put(rt);
		dev->stats.collisions++;
		goto tx_error;
	}
	tos = ip_tunnel_ecn_encap(tos, inner_iph