// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *	NET3:	Implementation of the ICMP protocol layer.
 *
 *		Alan Cox, <alan@lxorguk.ukuu.org.uk>
 *
 *	Some of the function names and the icmp unreach table for this
 *	module were derived from [icmp.c 1.0.11 06/02/93] by
 *	Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
 *	Other than that this module is a complete rewrite.
 *
 *	Fixes:
 *	Clemens Fruhwirth	:	introduce global icmp rate limiting
 *					with icmp type masking ability instead
 *					of broken per type icmp timeouts.
 *		Mike Shaver	:	RFC1122 checks.
 *		Alan Cox	:	Multicast ping reply as self.
 *		Alan Cox	:	Fix atomicity lockup in ip_build_xmit
 *					call.
 *		Alan Cox	:	Added 216,128 byte paths to the MTU
 *					code.
 *		Martin Mares	:	RFC1812 checks.
 *		Martin Mares	:	Can be configured to follow redirects
 *					if acting as a router _without_ a
 *					routing protocol (RFC 1812).
 *		Martin Mares	:	Echo requests may be configured to
 *					be ignored (RFC 1812).
 *		Martin Mares	:	Limitation of ICMP error message
 *					transmit rate (RFC 1812).
 *		Martin Mares	:	TOS and Precedence set correctly
 *					(RFC 1812).
 *		Martin Mares	:	Now copying as much data from the
 *					original packet as we can without
 *					exceeding 576 bytes (RFC 1812).
 *	Willy Konynenberg	:	Transparent proxying support.
 *		Keith Owens	:	RFC1191 correction for 4.2BSD based
 *					path MTU bug.
 *		Thomas Quinot	:	ICMP Dest Unreach codes up to 15 are
 *					valid (RFC 1812).
 *		Andi Kleen	:	Check all packet lengths properly
 *					and moved all kfree_skb() up to
 *					icmp_rcv.
 *		Andi Kleen	:	Move the rate limit bookkeeping
 *					into the dest entry and use a token
 *					bucket filter (thanks to ANK). Make
 *					the rates sysctl configurable.
 *		Yu Tianli	:	Fixed two ugly bugs in icmp_send
 *					- IP option length was accounted wrongly
 *					- ICMP header length was not accounted
 *					  at all.
 *              Tristan Greaves :       Added sysctl option to ignore bogus
 *              			broadcast responses from broken routers.
 *
 * To Fix:
 *
 *	- Should use skb_pull() instead of all the manual checking.
 *	  This would also greatly simply some upper layer error handlers. --AK
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/types.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/nospec.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/string.h>
#include <linux/netfilter_ipv4.h>
#include <linux/slab.h>
#include <net/flow.h>
#include <net/snmp.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/protocol.h>
#include <net/icmp.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/raw.h>
#include <net/ping.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <net/checksum.h>
#include <net/xfrm.h>
#include <net/inet_common.h>
#include <net/ip_fib.h>
#include <net/l3mdev.h>
#include <net/addrconf.h>
#include <net/inet_dscp.h>
#define CREATE_TRACE_POINTS
#include <trace/events/icmp.h>

/*
 *	Build xmit assembly blocks
 */

struct icmp_bxm {
	struct sk_buff *skb;
	int offset;
	int data_len;

	struct {
		struct icmphdr icmph;
		__be32	       times[3];
	} data;
	int head_len;

	/* Must be last as it ends in a flexible-array member. */
	struct ip_options_rcu replyopts;
};

/* An array of errno for error messages from dest unreach. */
/* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */

const struct icmp_err icmp_err_convert[] = {
	{
		.errno = ENETUNREACH,	/* ICMP_NET_UNREACH */
		.fatal = 0,
	},
	{
		.errno = EHOSTUNREACH,	/* ICMP_HOST_UNREACH */
		.fatal = 0,
	},
	{
		.errno = ENOPROTOOPT	/* ICMP_PROT_UNREACH */,
		.fatal = 1,
	},
	{
		.errno = ECONNREFUSED,	/* ICMP_PORT_UNREACH */
		.fatal = 1,
	},
	{
		.errno = EMSGSIZE,	/* ICMP_FRAG_NEEDED */
		.fatal = 0,
	},
	{
		.errno = EOPNOTSUPP,	/* ICMP_SR_FAILED */
		.fatal = 0,
	},
	{
		.errno = ENETUNREACH,	/* ICMP_NET_UNKNOWN */
		.fatal = 1,
	},
	{
		.errno = EHOSTDOWN,	/* ICMP_HOST_UNKNOWN */
		.fatal = 1,
	},
	{
		.errno = ENONET,	/* ICMP_HOST_ISOLATED */
		.fatal = 1,
	},
	{
		.errno = ENETUNREACH,	/* ICMP_NET_ANO	*/
		.fatal = 1,
	},
	{
		.errno = EHOSTUNREACH,	/* ICMP_HOST_ANO */
		.fatal = 1,
	},
	{
		.errno = ENETUNREACH,	/* ICMP_NET_UNR_TOS */
		.fatal = 0,
	},
	{
		.errno = EHOSTUNREACH,	/* ICMP_HOST_UNR_TOS */
		.fatal = 0,
	},
	{
		.errno = EHOSTUNREACH,	/* ICMP_PKT_FILTERED */
		.fatal = 1,
	},
	{
		.errno = EHOSTUNREACH,	/* ICMP_PREC_VIOLATION */
		.fatal = 1,
	},
	{
		.errno = EHOSTUNREACH,	/* ICMP_PREC_CUTOFF */
		.fatal = 1,
	},
};
EXPORT_SYMBOL(icmp_err_convert);

/*
 *	ICMP control array. This specifies what to do with each ICMP.
 */

struct icmp_control {
	enum skb_drop_reason (*handler)(struct sk_buff *skb);
	short   error;		/* This ICMP is classed as an error message */
};

static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];

static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);

/* Called with BH disabled */
static inline struct sock *icmp_xmit_lock(struct net *net)
{
	struct sock *sk;

	sk = this_cpu_read(ipv4_icmp_sk);

	if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
		/* This can happen if the output path signals a
		 * dst_link_failure() for an outgoing ICMP packet.
		 */
		return NULL;
	}
	sock_net_set(sk, net);
	return sk;
}

static inline void icmp_xmit_unlock(struct sock *sk)
{
	sock_net_set(sk, &init_net);
	spin_unlock(&sk->sk_lock.slock);
}

/**
 * icmp_global_allow - Are we allowed to send one more ICMP message ?
 * @net: network namespace
 *
 * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
 * Returns false if we reached the limit and can not send another packet.
 * Works in tandem with icmp_global_consume().
 */
bool icmp_global_allow(struct net *net)
{
	u32 delta, now, oldstamp;
	int incr, new, old;

	/* Note: many cpus could find this condition true.
	 * Then later icmp_global_consume() could consume more credits,
	 * this is an acceptable race.
	 */
	if (atomic_read(&net->ipv4.icmp_global_credit) > 0)
		return true;

	now = jiffies;
	oldstamp = READ_ONCE(net->ipv4.icmp_global_stamp);
	delta = min_t(u32, now - oldstamp, HZ);
	if (delta < HZ / 50)
		return false;

	incr = READ_ONCE(net->ipv4.sysctl_icmp_msgs_per_sec);
	incr = div_u64((u64)incr * delta, HZ);
	if (!incr)
		return false;

	if (cmpxchg(&net->ipv4.icmp_global_stamp, oldstamp, now) == oldstamp) {
		old = atomic_read(&net->ipv4.icmp_global_credit);
		do {
			new = min(old + incr, READ_ONCE(net->ipv4.sysctl_icmp_msgs_burst));
		} while (!atomic_try_cmpxchg(&net->ipv4.icmp_global_credit, &old, new));
	}
	return true;
}

void icmp_global_consume(struct net *net)
{
	int credits = get_random_u32_below(3);

	/* Note: this might make icmp_global.credit negative. */
	if (credits)
		atomic_sub(credits, &net->ipv4.icmp_global_credit);
}

static bool icmpv4_mask_allow(struct net *net, int type, int code)
{
	if (type > NR_ICMP_TYPES)
		return true;

	/* Don't limit PMTU discovery. */
	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
		return true;

	/* Limit if icmp type is enabled in ratemask. */
	if (!((1 << type) & READ_ONCE(net->ipv4.sysctl_icmp_ratemask)))
		return true;

	return false;
}

static bool icmpv4_global_allow(struct net *net, int type, int code,
				bool *apply_ratelimit)
{
	if (icmpv4_mask_allow(net, type, code))
		return true;

	if (icmp_global_allow(net)) {
		*apply_ratelimit = true;
		return true;
	}
	__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
	return false;
}

/*
 *	Send an ICMP frame.
 */

static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
			       struct flowi4 *fl4, int type, int code,
			       bool apply_ratelimit)
{
	struct dst_entry *dst = &rt->dst;
	struct inet_peer *peer;
	struct net_device *dev;
	int peer_timeout;
	bool rc = true;

	if (!apply_ratelimit)
		return true;

	peer_timeout = READ_ONCE(net->ipv4.sysctl_icmp_ratelimit);
	if (!peer_timeout)
		goto out;

	/* No rate limit on loopback */
	rcu_read_lock();
	dev = dst_dev_rcu(dst);
	if (dev && (dev->flags & IFF_LOOPBACK))
		goto out_unlock;

	peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr,
			       l3mdev_master_ifindex_rcu(dev));
	rc = inet_peer_xrlim_allow(peer, peer_timeout);

out_unlock:
	rcu_read_unlock();
out:
	if (!rc)
		__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
	else
		icmp_global_consume(net);
	return rc;
}

/*
 *	Maintain the counters used in the SNMP statistics for outgoing ICMP
 */
void icmp_out_count(struct net *net, unsigned char type)
{
	ICMPMSGOUT_INC_STATS(net, type);
	ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
}

/*
 *	Checksum each fragment, and on the first include the headers and final
 *	checksum.
 */
static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
			  struct sk_buff *skb)
{
	DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
			IP_OPTIONS_DATA_FIXED_SIZE);
	__wsum csum;

	icmp_param = from;

	csum = skb_copy_and_csum_bits(icmp_param->skb,
				      icmp_param->offset + offset,
				      to, len);

	skb->csum = csum_block_add(skb->csum, csum, odd);
	if (icmp_param->data.icmph.type <= NR_ICMP_TYPES &&
	    icmp_pointers[array_index_nospec(icmp_param->data.icmph.type,
					     NR_ICMP_TYPES + 1)].error)
		nf_ct_attach(skb, icmp_param->skb);
	return 0;
}

static void icmp_push_reply(struct sock *sk,
			    struct icmp_bxm *icmp_param,
			    struct flowi4 *fl4,
			    struct ipcm_cookie *ipc, struct rtable **rt)
{
	struct sk_buff *skb;

	if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
			   icmp_param->data_len+icmp_param->head_len,
			   icmp_param->head_len,
			   ipc, rt, MSG_DONTWAIT) < 0) {
		__ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
		ip_flush_pending_frames(sk);
	} else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
		struct icmphdr *icmph = icmp_hdr(skb);
		__wsum csum;
		struct sk_buff *skb1;

		csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
						 (char *)icmph,
						 icmp_param->head_len);
		skb_queue_walk(&sk->sk_write_queue, skb1) {
			csum = csum_add(csum, skb1->csum);
		}
		icmph->checksum = csum_fold(csum);
		skb->ip_summed = CHECKSUM_NONE;
		ip_push_pending_frames(sk, fl4);
	}
}

/*
 *	Driving logic for building and sending ICMP messages.
 */

static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
{
	struct rtable *rt = skb_rtable(skb);
	struct net *net = dev_net_rcu(rt->dst.dev);
	bool apply_ratelimit = false;
	struct ipcm_cookie ipc;
	struct flowi4 fl4;
	struct sock *sk;
	__be32 daddr, saddr;
	u32 mark = IP4_REPLY_MARK(net, skb->mark);
	int type = icmp_param->data.icmph.type;
	int code = icmp_param->data.icmph.code;

	if (ip_options_echo(net, &icmp_param->replyopts.opt, skb))
		return;

	/* Needed by both icmpv4_global_allow and icmp_xmit_lock */
	local_bh_disable();

	/* is global icmp_msgs_per_sec exhausted ? */
	if (!icmpv4_global_allow(net, type, code, &apply_ratelimit))
		goto out_bh_enable;

	sk = icmp_xmit_lock(net);
	if (!sk)
		goto out_bh_enable;

	icmp_param->data.icmph.checksum = 0;

	ipcm_init(&ipc);
	ipc.tos = ip_hdr(skb)->tos;
	ipc.sockc.mark = mark;
	daddr = ipc.addr = ip_hdr(skb)->saddr;
	saddr = fib_compute_spec_dst(skb);

	if (icmp_param->replyopts.opt.optlen) {
		ipc.opt = &icmp_param->replyopts;
		if (ipc.opt->opt.srr)
			daddr = icmp_param->replyopts.opt.faddr;
	}
	memset(&fl4, 0, sizeof(fl4));
	fl4.daddr = daddr;
	fl4.saddr = saddr;
	fl4.flowi4_mark = mark;
	fl4.flowi4_uid = sock_net_uid(net, NULL);
	fl4.flowi4_dscp = ip4h_dscp(ip_hdr(skb));
	fl4.flowi4_proto = IPPROTO_ICMP;
	fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
	security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
	rt = ip_route_output_key(net, &fl4);
	if (IS_ERR(rt))
		goto out_unlock;
	if (icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
		icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
	ip_rt_put(rt);
out_unlock:
	icmp_xmit_unlock(sk);
out_bh_enable:
	local_bh_enable();
}

/*
 * The device used for looking up which routing table to use for sending an ICMP
 * error is preferably the source whenever it is set, which should ensure the
 * icmp error can be sent to the source host, else lookup using the routing
 * table of the destination device, else use the main routing table (index 0).
 */
static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
{
	struct net_device *dev = skb->dev;
	const struct dst_entry *dst;

	if (dev)
		return dev;
	dst = skb_dst(skb);
	return dst ? dst_dev(dst) : NULL;
}

static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4,
					struct sk_buff *skb_in,
					const struct iphdr *iph, __be32 saddr,
					dscp_t dscp, u32 mark, int type,
					int code, struct icmp_bxm *param)
{
	struct net_device *route_lookup_dev;
	struct dst_entry *dst, *dst2;
	struct rtable *rt, *rt2;
	struct flowi4 fl4_dec;
	int err;

	memset(fl4, 0, sizeof(*fl4));
	fl4->daddr = (param->replyopts.opt.srr ?
		      param->replyopts.opt.faddr : iph->saddr);
	fl4->saddr = saddr;
	fl4->flowi4_mark = mark;
	fl4->flowi4_uid = sock_net_uid(net, NULL);
	fl4->flowi4_dscp = dscp;
	fl4->flowi4_proto = IPPROTO_ICMP;
	fl4->fl4_icmp_type = type;
	fl4->fl4_icmp_code = code;
	route_lookup_dev = icmp_get_route_lookup_dev(skb_in);
	fl4->flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);

	security_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));
	rt = ip_route_output_key_hash(net, fl4, skb_in);
	if (IS_ERR(rt))
		return rt;

	/* No need to clone since we're just using its address. */
	rt2 = rt;

	dst = xfrm_lookup(net, &rt->dst,
			  flowi4_to_flowi(fl4), NULL, 0);
	rt = dst_rtable(dst);
	if (!IS_ERR(dst)) {
		if (rt != rt2)
			return rt;
		if (inet_addr_type_dev_table(net, route_lookup_dev,
					     fl4->daddr) == RTN_LOCAL)
			return rt;
	} else if (PTR_ERR(dst) == -EPERM) {
		rt = NULL;
	} else {
		return rt;
	}
	err = xfrm_decode_session_reverse(net, skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
	if (err)
		goto relookup_failed;

	if (inet_addr_type_dev_table(net, route_lookup_dev,
				     fl4_dec.saddr) == RTN_LOCAL) {
		rt2 = __ip_route_output_key(net, &fl4_dec);
		if (IS_ERR(rt2))
			err = PTR_ERR(rt2);
	} else {
		struct flowi4 fl4_2 = fl4_dec;
		unsigned long orefdst;

		swap(fl4_2.daddr, fl4_2.saddr);
		switch (fl4_2.flowi4_proto) {
		case IPPROTO_TCP:
		case IPPROTO_UDP:
		case IPPROTO_SCTP:
		case IPPROTO_DCCP:
			swap(fl4_2.fl4_sport, fl4_2.fl4_dport);
			break;
		}

		fl4_2.flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);
		fl4_2.flowi4_flags |= FLOWI_FLAG_ANYSRC;

		rt2 = __ip_route_output_key(net, &fl4_2);
		if (IS_ERR(rt2)) {
			err = PTR_ERR(rt2);
			goto relookup_failed;
		}
		/* Ugh! */
		orefdst = skb_dstref_steal(skb_in);
		err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
				     dscp, rt2->dst.dev) ? -EINVAL : 0;

		dst_release(&rt2->dst);
		rt2 = skb_rtable(skb_in);
		/* steal dst entry from skb_in, don't drop refcnt */
		skb_dstref_steal(skb_in);
		skb_dstref_restore(skb_in, orefdst);

		/*
		 * At this point, fl4_dec.daddr should NOT be local (we
		 * checked fl4_dec.saddr above). However, a race condition
		 * may occur if the address is added to the interface
		 * concurrently. In that case, ip_route_input() returns a
		 * LOCAL route with dst.output=ip_rt_bug, which must not
		 * be used for output.
		 */
		if (!err && rt2 && rt2->rt_type == RTN_LOCAL) {
			net_warn_ratelimited("detected local route for %pI4 during ICMP sending, src %pI4\n",
					     &fl4_dec.daddr, &fl4_dec.saddr);
			dst_release(&rt2->dst);
			err = -EINVAL;
		}
	}

	if (err)
		goto relookup_failed;

	dst2 = xfrm_lookup(net, &rt2->dst, flowi4_to_flowi(&fl4_dec), NULL,
			   XFRM_LOOKUP_ICMP);
	rt2 = dst_rtable(dst2);
	if (!IS_ERR(dst2)) {
		dst_release(&rt->dst);
		rt = rt2;
	} else if (PTR_ERR(dst2) == -EPERM) {
		if (rt)
			dst_release(&rt->dst);
		return rt2;
	} else {
		err = PTR_ERR(dst2);
		goto relookup_failed;
	}
	return rt;

relookup_failed:
	if (rt)
		return rt;
	return ERR_PTR(err);
}

struct icmp_ext_iio_addr4_subobj {
	__be16 afi;
	__be16 reserved;
	__be32 addr4;
};

static unsigned int icmp_ext_iio_len(void)
{
	return sizeof(struct icmp_extobj_hdr) +
		/* ifIndex */
		sizeof(__be32) +
		/* Interface Address Sub-Object */
		sizeof(struct icmp_ext_iio_addr4_subobj) +
		/* Interface Name Sub-Object. Length must be a multiple of 4
		 * bytes.
		 */
		ALIGN(sizeof(struct icmp_ext_iio_name_subobj), 4) +
		/* MTU */
		sizeof(__be32);
}

static unsigned int icmp_ext_max_len(u8 ext_objs)
{
	unsigned int ext_max_len;

	ext_max_len = sizeof(struct icmp_ext_hdr);

	if (ext_objs & BIT(ICMP_ERR_EXT_IIO_IIF))
		ext_max_len += icmp_ext_iio_len();

	return ext_max_len;
}

static __be32 icmp_ext_iio_addr4_find(const struct net_device *dev)
{
	struct in_device *in_dev;
	struct in_ifaddr *ifa;

	in_dev = __in_dev_get_rcu(dev);
	if (!in_dev)
		return 0;

	/* It is unclear from RFC 5837 which IP address should be chosen, but
	 * it makes sense to choose a global unicast address.
	 */
	in_dev_for_each_ifa_rcu(ifa, in_dev) {
		if (READ_ONCE(ifa->ifa_flags) & IFA_F_SECONDARY)
			continue;
		if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
		    ipv4_is_multicast(ifa->ifa_address))
			continue;
		return ifa->ifa_address;
	}

	return 0;
}

static void icmp_ext_iio_iif_append(struct net *net, struct sk_buff *skb,
				    int iif)
{
	struct icmp_ext_iio_name_subobj *name_subobj;
	struct icmp_extobj_hdr *objh;
	struct net_device *dev;
	__be32 data;

	if (!iif)
		return;

	/* Add the fields in the order specified by RFC 5837. */
	objh = skb_put(skb, sizeof(*objh));
	objh->class_num = ICMP_EXT_OBJ_CLASS_IIO;
	objh->class_type = ICMP_EXT_CTYPE_IIO_ROLE(ICMP_EXT_CTYPE_IIO_ROLE_IIF);

	data = htonl(iif);
	skb_put_data(skb, &data, sizeof(__be32));
	objh->class_type |= ICMP_EXT_CTYPE_IIO_IFINDEX;

	rcu_read_lock();

	dev = dev_get_by_index_rcu(net, iif);
	if (!dev)
		goto out;

	data = icmp_ext_iio_addr4_find(dev);
	if (data) {
		struct icmp_ext_iio_addr4_subobj *addr4_subobj;

		addr4_subobj = skb_put_zero(skb, sizeof(*addr4_subobj));
		addr4_subobj->afi = htons(ICMP_AFI_IP);
		addr4_subobj->addr4 = data;
		objh->class_type |= ICMP_EXT_CTYPE_IIO_IPADDR;
	}

	name_subobj = skb_put_zero(skb, ALIGN(sizeof(*name_subobj), 4));
	name_subobj->len = ALIGN(sizeof(*name_subobj), 4);
	netdev_copy_name(dev, name_subobj->name);
	objh->class_type |= ICMP_EXT_CTYPE_IIO_NAME;

	data = htonl(READ_ONCE(dev->mtu));
	skb_put_data(skb, &data, sizeof(__be32));
	objh->class_type |= ICMP_EXT_CTYPE_IIO_MTU;

out:
	rcu_read_unlock();
	objh->length = htons(skb_tail_pointer(skb) - (unsigned char *)objh);
}

static void icmp_ext_objs_append(struct net *net, struct sk_buff *skb,
				 u8 ext_objs, int iif)
{
	if (ext_objs & BIT(ICMP_ERR_EXT_IIO_IIF))
		icmp_ext_iio_iif_append(net, skb, iif);
}

static struct sk_buff *
icmp_ext_append(struct net *net, struct sk_buff *skb_in, struct icmphdr *icmph,
		unsigned int room, int iif)
{
	unsigned int payload_len, ext_max_len, ext_len;
	struct icmp_ext_hdr *ext_hdr;
	struct sk_buff *skb;
	u8 ext_objs;
	int nhoff;

	switch (icmph->type) {
	case ICMP_DEST_UNREACH:
	case ICMP_TIME_EXCEEDED:
	case ICMP_PARAMETERPROB:
		break;
	default:
		return NULL;
	}

	ext_objs = READ_ONCE(net->ipv4.sysctl_icmp_errors_extension_mask);
	if (!ext_objs)
		return NULL;

	ext_max_len = icmp_ext_max_len(ext_objs);
	if (ICMP_EXT_ORIG_DGRAM_MIN_LEN + ext_max_len > room)
		return NULL;

	skb = skb_clone(skb_in, GFP_ATOMIC);
	if (!skb)
		return NULL;

	nhoff = skb_network_offset(skb);
	payload_len = min(skb->len - nhoff, ICMP_EXT_ORIG_DGRAM_MIN_LEN);

	if (!pskb_network_may_pull(skb, payload_len))
		goto free_skb;

	if (pskb_trim(skb, nhoff + ICMP_EXT_ORIG_DGRAM_MIN_LEN) ||
	    __skb_put_padto(skb, nhoff + ICMP_EXT_ORIG_DGRAM_MIN_LEN, false))
		goto free_skb;

	if (pskb_expand_head(skb, 0, ext_max_len, GFP_ATOMIC))
		goto free_skb;

	ext_hdr = skb_put_zero(skb, sizeof(*ext_hdr));
	ext_hdr->version = ICMP_EXT_VERSION_2;

	icmp_ext_objs_append(net, skb, ext_objs, iif);

	/* Do not send an empty extension structure. */
	ext_len = skb_tail_pointer(skb) - (unsigned char *)ext_hdr;
	if (ext_len == sizeof(*ext_hdr))
		goto free_skb;

	ext_hdr->checksum = ip_compute_csum(ext_hdr, ext_len);
	/* The length of the original datagram in 32-bit words (RFC 4884). */
	icmph->un.reserved[1] = ICMP_EXT_ORIG_DGRAM_MIN_LEN / sizeof(u32);

	return skb;

free_skb:
	consume_skb(skb);
	return NULL;
}

/*
 *	Send an ICMP message in response to a situation
 *
 *	RFC 1122: 3.2.2	MUST send at least the IP header and 8 bytes of header.
 *		  MAY send more (we do).
 *			MUST NOT change this header information.
 *			MUST NOT reply to a multicast/broadcast IP address.
 *			MUST NOT reply to a multicast/broadcast MAC address.
 *			MUST reply to only the first fragment.
 */

void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
		 const struct inet_skb_parm *parm)
{
	DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
			IP_OPTIONS_DATA_FIXED_SIZE);
	struct iphdr *iph;
	int room;
	struct rtable *rt = skb_rtable(skb_in);
	bool apply_ratelimit = false;
	struct sk_buff *ext_skb;
	struct ipcm_cookie ipc;
	struct flowi4 fl4;
	__be32 saddr;
	u8  tos;
	u32 mark;
	struct net *net;
	struct sock *sk;

	if (!rt)
		return;

	rcu_read_lock();

	if (rt->dst.dev)
		net = dev_net_rcu(rt->dst.dev);
	else if (skb_in->dev)
		net = dev_net_rcu(skb_in->dev);
	else
		goto out;

	/*
	 *	Find the original header. It is expected to be valid, of course.
	 *	Check this, icmp_send is called from the most obscure devices
	 *	sometimes.
	 */
	iph = ip_hdr(skb_in);

	if ((u8 *)iph < skb_in->head ||
	    (skb_network_header(skb_in) + sizeof(*iph)) >
	    skb_tail_pointer(skb_in))
		goto out;

	/*
	 *	No replies to physical multicast/broadcast
	 */
	if (skb_in->pkt_type != PACKET_HOST)
		goto out;

	/*
	 *	Now check at the protocol level
	 */
	if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
		goto out;

	/*
	 *	Only reply to fragment 0. We byte re-order the constant
	 *	mask for efficiency.
	 */
	if (iph->frag_off & htons(IP_OFFSET))
		goto out;

	/*
	 *	If we send an ICMP error to an ICMP error a mess would result..
	 */
	if (icmp_pointers[type].error) {
		/*
		 *	We are an error, check if we are replying to an
		 *	ICMP error
		 */
		if (iph->protocol == IPPROTO_ICMP) {
			u8 _inner_type, *itp;

			itp = skb_header_pointer(skb_in,
						 skb_network_header(skb_in) +
						 (iph->ihl << 2) +
						 offsetof(struct icmphdr,
							  type) -
						 skb_in->data,
						 sizeof(_inner_type),
						 &_inner_type);
			if (!itp)
				goto out;

			/*
			 *	Assume any unknown ICMP type is an error. This
			 *	isn't specified by the RFC, but think about it..
			 */
			if (*itp > NR_ICMP_TYPES ||
			    icmp_pointers[*itp].error)
				goto out;
		}
	}

	/* Needed by both icmpv4_global_allow and icmp_xmit_lock */
	local_bh_disable();

	/* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
	 * incoming dev is loopback.  If outgoing dev change to not be
	 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
	 */
	if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
	      !icmpv4_global_allow(net, type, code, &apply_ratelimit))
		goto out_bh_enable;

	sk = icmp_xmit_lock(net);
	if (!sk)
		goto out_bh_enable;

	/*
	 *	Construct source address and options.
	 */

	saddr = iph->daddr;
	if (!(rt->rt_flags & RTCF_LOCAL)) {
		struct net_device *dev = NULL;

		rcu_read_lock();
		if (rt_is_input_route(rt) &&
		    READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
			dev = dev_get_by_index_rcu(net, parm->iif ? parm->iif :
						   inet_iif(skb_in));

		if (dev)
			saddr = inet_select_addr(dev, iph->saddr,
						 RT_SCOPE_LINK);
		else
			saddr = 0;
		rcu_read_unlock();
	}

	tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
					   IPTOS_PREC_INTERNETCONTROL) :
					   iph->tos;
	mark = IP4_REPLY_MARK(net, skb_in->mark);

	if (__ip_options_echo(net, &icmp_param->replyopts.opt, skb_in,
			      &parm->opt))
		goto out_unlock;


	/*
	 *	Prepare data for ICMP header.
	 */

	icmp_param->data.icmph.type	 = type;
	icmp_param->data.icmph.code	 = code;
	icmp_param->data.icmph.un.gateway = info;
	icmp_param->data.icmph.checksum	 = 0;
	icmp_param->skb	  = skb_in;
	icmp_param->offset = skb_network_offset(skb_in);
	ipcm_init(&ipc);
	ipc.tos = tos;
	ipc.addr = iph->saddr;
	ipc.opt = &icmp_param->replyopts;
	ipc.sockc.mark = mark;

	rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr,
			       inet_dsfield_to_dscp(tos), mark, type, code,
			       icmp_param);
	if (IS_ERR(rt))
		goto out_unlock;

	if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
		goto ende;

	/* peer icmp_ratelimit */
	if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
		goto ende;

	/* RFC says return as much as we can without exceeding 576 bytes. */

	room = dst4_mtu(&rt->dst);
	if (room > 576)
		room = 576;
	room -= sizeof(struct iphdr) + icmp_param->replyopts.opt.optlen;
	room -= sizeof(struct icmphdr);
	/* Guard against tiny mtu. We need to include at least one
	 * IP network header for this message to make any sense.
	 */
	if (room <= (int)sizeof(struct iphdr))
		goto ende;

	ext_skb = icmp_ext_append(net, skb_in, &icmp_param->data.icmph, room,
				  parm->iif);
	if (ext_skb)
		icmp_param->skb = ext_skb;

	icmp_param->data_len = icmp_param->skb->len - icmp_param->offset;
	if (icmp_param->data_len > room)
		icmp_param->data_len = room;
	icmp_param->head_len = sizeof(struct icmphdr);

	/* if we don't have a source address at this point, fall back to the
	 * dummy address instead of sending out a packet with a source address
	 * of 0.0.0.0
	 */
	if (!fl4.saddr)
		fl4.saddr = htonl(INADDR_DUMMY);

	trace_icmp_send(skb_in, type, code);

	icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);

	if (ext_skb)
		consume_skb(ext_skb);
ende:
	ip_rt_put(rt);
out_unlock:
	icmp_xmit_unlock(sk);
out_bh_enable:
	local_bh_enable();
out:
	rcu_read_unlock();
}
EXPORT_SYMBOL(__icmp_send);

#if IS_ENABLED(CONFIG_NF_NAT)
#include <net/netfilter/nf_conntrack.h>
void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
{
	struct sk_buff *cloned_skb = NULL;
	enum ip_conntrack_info ctinfo;
	enum ip_conntrack_dir dir;
	struct inet_skb_parm parm;
	struct nf_conn *ct;
	__be32 orig_ip;

	memset(&parm, 0, sizeof(parm));
	ct = nf_ct_get(skb_in, &ctinfo);
	if (!ct || !(READ_ONCE(ct->status) & IPS_NAT_MASK)) {
		__icmp_send(skb_in, type, code, info, &parm);
		return;
	}

	if (skb_shared(skb_in))
		skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);

	if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
	    (skb_network_header(skb_in) + sizeof(struct iphdr)) >
	    skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
	    skb_network_offset(skb_in) + sizeof(struct iphdr))))
		goto out;

	orig_ip = ip_hdr(skb_in)->saddr;
	dir = CTINFO2DIR(ctinfo);
	ip_hdr(skb_in)->saddr = ct->tuplehash[dir].tuple.src.u3.ip;
	__icmp_send(skb_in, type, code, info, &parm);
	ip_hdr(skb_in)->saddr = orig_ip;
out:
	consume_skb(cloned_skb);
}
EXPORT_SYMBOL(icmp_ndo_send);
#endif

static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
{
	const struct iphdr *iph = (const struct iphdr *)skb->data;
	const struct net_protocol *ipprot;
	int protocol = iph->protocol;

	/* Checkin full IP header plus 8 bytes of protocol to
	 * avoid additional coding at protocol handlers.
	 */
	if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
		goto out;

	/* IPPROTO_RAW sockets are not supposed to receive anything. */
	if (protocol == IPPROTO_RAW)
		goto out;

	raw_icmp_error(skb, protocol, info);

	ipprot = rcu_dereference(inet_protos[protocol]);
	if (ipprot && ipprot->err_handler)
		ipprot->err_handler(skb, info);
	return;

out:
	__ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
}

static bool icmp_tag_validation(int proto)
{
	const struct net_protocol *ipprot;
	bool ok;

	rcu_read_lock();
	ipprot = rcu_dereference(inet_protos[proto]);
	ok = ipprot ? ipprot->icmp_strict_tag_validation : false;
	rcu_read_unlock();
	return ok;
}

/*
 *	Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
 *	ICMP_PARAMETERPROB.
 */

static enum skb_drop_reason icmp_unreach(struct sk_buff *skb)
{
	enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
	const struct iphdr *iph;
	struct icmphdr *icmph;
	struct net *net;
	u32 info = 0;

	net = skb_dst_dev_net_rcu(skb);

	/*
	 *	Incomplete header ?
	 * 	Only checks for the IP header, there should be an
	 *	additional check for longer headers in upper levels.
	 */

	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
		goto out_err;

	icmph = icmp_hdr(skb);
	iph   = (const struct iphdr *)skb->data;

	if (iph->ihl < 5)  { /* Mangled header, drop. */
		reason = SKB_DROP_REASON_IP_INHDR;
		goto out_err;
	}

	switch (icmph->type) {
	case ICMP_DEST_UNREACH:
		switch (icmph->code & 15) {
		case ICMP_NET_UNREACH:
		case ICMP_HOST_UNREACH:
		case ICMP_PROT_UNREACH:
		case ICMP_PORT_UNREACH:
			break;
		case ICMP_FRAG_NEEDED:
			/* for documentation of the ip_no_pmtu_disc
			 * values please see
			 * Documentation/networking/ip-sysctl.rst
			 */
			switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
			default:
				net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
						    &iph->daddr);
				break;
			case 2:
				goto out;
			case 3:
				if (!icmp_tag_validation(iph->protocol))
					goto out;
				fallthrough;
			case 0:
				info = ntohs(icmph->un.frag.mtu);
			}
			break;
		case ICMP_SR_FAILED:
			net_dbg_ratelimited("%pI4: Source Route Failed\n",
					    &iph->daddr);
			break;
		default:
			break;
		}
		if (icmph->code > NR_ICMP_UNREACH)
			goto out;
		break;
	case ICMP_PARAMETERPROB:
		info = ntohl(icmph->un.gateway) >> 24;
		break;
	case ICMP_TIME_EXCEEDED:
		__ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
		if (icmph->code == ICMP_EXC_FRAGTIME)
			goto out;
		break;
	}

	/*
	 *	Throw it at our lower layers
	 *
	 *	RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
	 *		  header.
	 *	RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
	 *		  transport layer.
	 *	RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
	 *		  transport layer.
	 */

	/*
	 *	Check the other end isn't violating RFC 1122. Some routers send
	 *	bogus responses to broadcast frames. If you see this message
	 *	first check your netmask matches at both ends, if it does then
	 *	get the other vendor to fix their kit.
	 */

	if (!READ_ONCE(net->ipv4.sysctl_icmp_ignore_bogus_error_responses) &&
	    inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
		net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
				     &ip_hdr(skb)->saddr,
				     icmph->type, icmph->code,
				     &iph->daddr, skb->dev->name);
		goto out;
	}

	icmp_socket_deliver(skb, info);

out:
	return reason;
out_err:
	__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
	return reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
}


/*
 *	Handle ICMP_REDIRECT.
 */

static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
{
	if (skb->len < sizeof(struct iphdr)) {
		__ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
		return SKB_DROP_REASON_PKT_TOO_SMALL;
	}

	if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
		/* there aught to be a stat */
		return SKB_DROP_REASON_NOMEM;
	}

	icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
	return SKB_NOT_DROPPED_YET;
}

/*
 *	Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") requests.
 *
 *	RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
 *		  requests.
 *	RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
 *		  included in the reply.
 *	RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
 *		  echo requests, MUST have default=NOT.
 *	RFC 8335: 8 MUST have a config option to enable/disable ICMP
 *		  Extended Echo Functionality, MUST be disabled by default
 *	See also WRT handling of options once they are done and working.
 */

static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
{
	DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
			IP_OPTIONS_DATA_FIXED_SIZE);
	struct net *net;

	net = skb_dst_dev_net_rcu(skb);
	/* should there be an ICMP stat for ignored echos? */
	if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
		return SKB_NOT_DROPPED_YET;

	icmp_param->data.icmph	   = *icmp_hdr(skb);
	icmp_param->skb		   = skb;
	icmp_param->offset	   = 0;
	icmp_param->data_len	   = skb->len;
	icmp_param->head_len	   = sizeof(struct icmphdr);

	if (icmp_param->data.icmph.type == ICMP_ECHO)
		icmp_param->data.icmph.type = ICMP_ECHOREPLY;
	else if (!icmp_build_probe(skb, &icmp_param->data.icmph))
		return SKB_NOT_DROPPED_YET;

	icmp_reply(icmp_param, skb);
	return SKB_NOT_DROPPED_YET;
}

/*	Helper for icmp_echo and icmpv6_echo_reply.
 *	Searches for net_device that matches PROBE interface identifier
 *		and builds PROBE reply message in icmphdr.
 *
 *	Returns false if PROBE responses are disabled via sysctl
 */

bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
{
	struct net *net = dev_net_rcu(skb->dev);
	struct icmp_ext_hdr *ext_hdr, _ext_hdr;
	struct icmp_ext_echo_iio *iio, _iio;
	struct inet6_dev *in6_dev;
	struct in_device *in_dev;
	struct net_device *dev;
	char buff[IFNAMSIZ];
	u16 ident_len;
	u8 status;

	if (!READ_ONCE(net->ipv4.sysctl_icmp_echo_enable_probe))
		return false;

	/* We currently only support probing interfaces on the proxy node
	 * Check to ensure L-bit is set
	 */
	if (!(ntohs(icmphdr->un.echo.sequence) & 1))
		return false;
	/* Clear status bits in reply message */
	icmphdr->un.echo.sequence &= htons(0xFF00);
	if (icmphdr->type == ICMP_EXT_ECHO)
		icmphdr->type = ICMP_EXT_ECHOREPLY;
	else
		icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
	ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
	/* Size of iio is class_type dependent.
	 * Only check header here and assign length based on ctype in the switch statement
	 */
	iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_iio);
	if (!ext_hdr || !iio)
		goto send_mal_query;
	if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
	    ntohs(iio->extobj_hdr.length) > sizeof(_iio))
		goto send_mal_query;
	ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
	iio = skb_header_pointer(skb, sizeof(_ext_hdr),
				 sizeof(iio->extobj_hdr) + ident_len, &_iio);
	if (!iio)
		goto send_mal_query;

	status = 0;
	dev = NULL;
	switch (iio->extobj_hdr.class_type) {
	case ICMP_EXT_ECHO_CTYPE_NAME:
		if (ident_len >= IFNAMSIZ)
			goto send_mal_query;
		memset(buff, 0, sizeof(buff));
		memcpy(buff, &iio->ident.name, ident_len);
		dev = dev_get_by_name(net, buff);
		break;
	case ICMP_EXT_ECHO_CTYPE_INDEX:
		if (ident_len != sizeof(iio->ident.ifindex))
			goto send_mal_query;
		dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
		break;
	case ICMP_EXT_ECHO_CTYPE_ADDR:
		if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
		    ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
				 iio->ident.addr.ctype3_hdr.addrlen)
			goto send_mal_query;
		switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
		case ICMP_AFI_IP:
			if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
				goto send_mal_query;
			dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr);
			break;
#if IS_ENABLED(CONFIG_IPV6)
		case ICMP_AFI_IP6:
			if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
				goto send_mal_query;
			dev = ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
			dev_hold(dev);
			break;
#endif
		default:
			goto send_mal_query;
		}
		break;
	default:
		goto send_mal_query;
	}
	if (!dev) {
		icmphdr->code = ICMP_EXT_CODE_NO_IF;
		return true;
	}
	/* Fill bits in reply message */
	if (dev->flags & IFF_UP)
		status |= ICMP_EXT_ECHOREPLY_ACTIVE;

	in_dev = __in_dev_get_rcu(dev);
	if (in_dev && rcu_access_pointer(in_dev->ifa_list))
		status |= ICMP_EXT_ECHOREPLY_IPV4;

	in6_dev = __in6_dev_get(dev);
	if (in6_dev && !list_empty(&in6_dev->addr_list))
		status |= ICMP_EXT_ECHOREPLY_IPV6;

	dev_put(dev);
	icmphdr->un.echo.sequence |= htons(status);
	return true;
send_mal_query:
	icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
	return true;
}

/*
 *	Handle ICMP Timestamp requests.
 *	RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
 *		  SHOULD be in the kernel for minimum random latency.
 *		  MUST be accurate to a few minutes.
 *		  MUST be updated at least at 15Hz.
 */
static enum skb_drop_reason icmp_timestamp(struct sk_buff *skb)
{
	DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
			IP_OPTIONS_DATA_FIXED_SIZE);
	/*
	 *	Too short.
	 */
	if (skb->len < 4)
		goto out_err;

	/*
	 *	Fill in the current time as ms since midnight UT:
	 */
	icmp_param->data.times[1] = inet_current_timestamp();
	icmp_param->data.times[2] = icmp_param->data.times[1];

	BUG_ON(skb_copy_bits(skb, 0, &icmp_param->data.times[0], 4));

	icmp_param->data.icmph	   = *icmp_hdr(skb);
	icmp_param->data.icmph.type = ICMP_TIMESTAMPREPLY;
	icmp_param->data.icmph.code = 0;
	icmp_param->skb		   = skb;
	icmp_param->offset	   = 0;
	icmp_param->data_len	   = 0;
	icmp_param->head_len	   = sizeof(struct icmphdr) + 12;
	icmp_reply(icmp_param, skb);
	return SKB_NOT_DROPPED_YET;

out_err:
	__ICMP_INC_STATS(skb_dst_dev_net_rcu(skb), ICMP_MIB_INERRORS);
	return SKB_DROP_REASON_PKT_TOO_SMALL;
}

static enum skb_drop_reason icmp_discard(struct sk_buff *skb)
{
	/* pretend it was a success */
	return SKB_NOT_DROPPED_YET;
}

/*
 *	Deal with incoming ICMP packets.
 */
int icmp_rcv(struct sk_buff *skb)
{
	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
	struct rtable *rt = skb_rtable(skb);
	struct net *net = dev_net_rcu(rt->dst.dev);
	struct icmphdr *icmph;

	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
		struct sec_path *sp = skb_sec_path(skb);
		int nh;

		if (!(sp && sp->xvec[sp->len - 1]->props.flags &
				 XFRM_STATE_ICMP)) {
			reason = SKB_DROP_REASON_XFRM_POLICY;
			goto drop;
		}

		if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
			goto drop;

		nh = skb_network_offset(skb);
		skb_set_network_header(skb, sizeof(*icmph));

		if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN,
						skb)) {
			reason = SKB_DROP_REASON_XFRM_POLICY;
			goto drop;
		}

		skb_set_network_header(skb, nh);
	}

	__ICMP_INC_STATS(net, ICMP_MIB_INMSGS);

	if (skb_checksum_simple_validate(skb))
		goto csum_error;

	if (!pskb_pull(skb, sizeof(*icmph)))
		goto error;

	icmph = icmp_hdr(skb);

	ICMPMSGIN_INC_STATS(net, icmph->type);

	/* Check for ICMP Extended Echo (PROBE) messages */
	if (icmph->type == ICMP_EXT_ECHO) {
		/* We can't use icmp_pointers[].handler() because it is an array of
		 * size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
		 */
		reason = icmp_echo(skb);
		goto reason_check;
	}

	/*
	 *	Parse the ICMP message
	 */

	if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
		/*
		 *	RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
		 *	  silently ignored (we let user decide with a sysctl).
		 *	RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
		 *	  discarded if to broadcast/multicast.
		 */
		if ((icmph->type == ICMP_ECHO ||
		     icmph->type == ICMP_TIMESTAMP) &&
		    READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
			reason = SKB_DROP_REASON_INVALID_PROTO;
			goto error;
		}
		if (icmph->type != ICMP_ECHO &&
		    icmph->type != ICMP_TIMESTAMP &&
		    icmph->type != ICMP_ADDRESS &&
		    icmph->type != ICMP_ADDRESSREPLY) {
			reason = SKB_DROP_REASON_INVALID_PROTO;
			goto error;
		}
	}

	if (icmph->type == ICMP_EXT_ECHOREPLY ||
	    icmph->type == ICMP_ECHOREPLY) {
		reason = ping_rcv(skb);
		return reason ? NET_RX_DROP : NET_RX_SUCCESS;
	}

	/*
	 *	18 is the highest 'known' ICMP type. Anything else is a mystery
	 *
	 *	RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
	 *		  discarded.
	 */
	if (icmph->type > NR_ICMP_TYPES) {
		reason = SKB_DROP_REASON_UNHANDLED_PROTO;
		goto error;
	}

	reason = icmp_pointers[icmph->type].handler(skb);
reason_check:
	if (!reason)  {
		consume_skb(skb);
		return NET_RX_SUCCESS;
	}

drop:
	kfree_skb_reason(skb, reason);
	return NET_RX_DROP;
csum_error:
	reason = SKB_DROP_REASON_ICMP_CSUM;
	__ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
error:
	__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
	goto drop;
}

static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
{
	struct icmp_extobj_hdr *objh, _objh;
	struct icmp_ext_hdr *exth, _exth;
	u16 olen;

	exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
	if (!exth)
		return false;
	if (exth->version != 2)
		return true;

	if (exth->checksum &&
	    csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
		return false;

	off += sizeof(_exth);
	while (off < skb->len) {
		objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
		if (!objh)
			return false;

		olen = ntohs(objh->length);
		if (olen < sizeof(_objh))
			return false;

		off += olen;
		if (off > skb->len)
			return false;
	}

	return true;
}

void ip_icmp_error_rfc4884(const struct sk_buff *skb,
			   struct sock_ee_data_rfc4884 *out,
			   int thlen, int off)
{
	int hlen;

	/* original datagram headers: end of icmph to payload (skb->data) */
	hlen = -skb_transport_offset(skb) - thlen;

	/* per rfc 4884: minimal datagram length of 128 bytes */
	if (off < 128 || off < hlen)
		return;

	/* kernel has stripped headers: return payload offset in bytes */
	off -= hlen;
	if (off + sizeof(struct icmp_ext_hdr) > skb->len)
		return;

	out->len = off;

	if (!ip_icmp_error_rfc4884_validate(skb, off))
		out->flags |= SO_EE_RFC4884_FLAG_INVALID;
}

int icmp_err(struct sk_buff *skb, u32 info)
{
	struct iphdr *iph = (struct iphdr *)skb->data;
	int offset = iph->ihl<<2;
	struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
	struct net *net = dev_net_rcu(skb->dev);
	int type = icmp_hdr(skb)->type;
	int code = icmp_hdr(skb)->code;

	/*
	 * Use ping_err to handle all icmp errors except those
	 * triggered by ICMP_ECHOREPLY which sent from kernel.
	 */
	if (icmph->type != ICMP_ECHOREPLY) {
		ping_err(skb, offset, info);
		return 0;
	}

	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
		ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
	else if (type == ICMP_REDIRECT)
		ipv4_redirect(skb, net, 0, IPPROTO_ICMP);

	return 0;
}

/*
 *	This table is the definition of how we handle ICMP.
 */
static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
	[ICMP_ECHOREPLY] = {
		.handler = ping_rcv,
	},
	[1] = {
		.handler = icmp_discard,
		.error = 1,
	},
	[2] = {
		.handler = icmp_discard,
		.error = 1,
	},
	[ICMP_DEST_UNREACH] = {
		.handler = icmp_unreach,
		.error = 1,
	},
	[ICMP_SOURCE_QUENCH] = {
		.handler = icmp_unreach,
		.error = 1,
	},
	[ICMP_REDIRECT] = {
		.handler = icmp_redirect,
		.error = 1,
	},
	[6] = {
		.handler = icmp_discard,
		.error = 1,
	},
	[7] = {
		.handler = icmp_discard,
		.error = 1,
	},
	[ICMP_ECHO] = {
		.handler = icmp_echo,
	},
	[9] = {
		.handler = icmp_discard,
		.error = 1,
	},
	[10] = {
		.handler = icmp_discard,
		.error = 1,
	},
	[ICMP_TIME_EXCEEDED] = {
		.handler = icmp_unreach,
		.error = 1,
	},
	[ICMP_PARAMETERPROB] = {
		.handler = icmp_unreach,
		.error = 1,
	},
	[ICMP_TIMESTAMP] = {
		.handler = icmp_timestamp,
	},
	[ICMP_TIMESTAMPREPLY] = {
		.handler = icmp_discard,
	},
	[ICMP_INFO_REQUEST] = {
		.handler = icmp_discard,
	},
	[ICMP_INFO_REPLY] = {
		.handler = icmp_discard,
	},
	[ICMP_ADDRESS] = {
		.handler = icmp_discard,
	},
	[ICMP_ADDRESSREPLY] = {
		.handler = icmp_discard,
	},
};

static int __net_init icmp_sk_init(struct net *net)
{
	/* Control parameters for ECHO replies. */
	net->ipv4.sysctl_icmp_echo_ignore_all = 0;
	net->ipv4.sysctl_icmp_echo_enable_probe = 0;
	net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;

	/* Control parameter - ignore bogus broadcast responses? */
	net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;

	/*
	 * 	Configurable global rate limit.
	 *
	 *	ratelimit defines tokens/packet consumed for dst->rate_token
	 *	bucket ratemask defines which icmp types are ratelimited by
	 *	setting	it's bit position.
	 *
	 *	default:
	 *	dest unreachable (3), source quench (4),
	 *	time exceeded (11), parameter problem (12)
	 */

	net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
	net->ipv4.sysctl_icmp_ratemask = 0x1818;
	net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
	net->ipv4.sysctl_icmp_errors_extension_mask = 0;
	net->ipv4.sysctl_icmp_msgs_per_sec = 10000;
	net->ipv4.sysctl_icmp_msgs_burst = 10000;

	return 0;
}

static struct pernet_operations __net_initdata icmp_sk_ops = {
       .init = icmp_sk_init,
};

int __init icmp_init(void)
{
	int err, i;

	for_each_possible_cpu(i) {
		struct sock *sk;

		err = inet_ctl_sock_create(&sk, PF_INET,
					   SOCK_RAW, IPPROTO_ICMP, &init_net);
		if (err < 0)
			return err;

		per_cpu(ipv4_icmp_sk, i) = sk;

		/* Enough space for 2 64K ICMP packets, including
		 * sk_buff/skb_shared_info struct overhead.
		 */
		sk->sk_sndbuf =	2 * SKB_TRUESIZE(64 * 1024);

		/*
		 * Speedup sock_wfree()
		 */
		sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
		inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
	}
	return register_pernet_subsys(&icmp_sk_ops);
}
