text: // 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/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/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>
  
  /*
   *	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;
  	struct ip_options_data 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 {
  	bool (*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];
  
  /*
   *	The ICMP socket(s). This is the most convenient way to flow control
   *	our ICMP output as well as maintain a clean interface throughout
   *	all layers. All Socketless IP sends will soon be gone.
   *
   *	On SMP we have one ICMP socket per-cpu.
   */
  static struct sock *icmp_sk(struct net *net)
  {
  	return this_cpu_read(*net->ipv4.icmp_sk);
  }
  
  /* Called with BH disabled */
  static inline struct sock *icmp_xmit_lock(struct net *net)
  {
  	struct sock *sk;
  
  	sk = icmp_sk(net);
  
  	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;
  	}
  	return sk;
  }
  
  static inline void icmp_xmit_unlock(struct sock *sk)
  {
  	spin_unlock(&sk->sk_lock.slock);
  }
  
  int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
  int sysctl_icmp_msgs_burst __read_mostly = 50;
  
  static struct {
  	spinlock_t	lock;
  	u32		credit;
  	u32		stamp;
  } icmp_global = {
  	.lock		= __SPIN_LOCK_UNLOCKED(icmp_global.lock),
  };
  
  /**
   * icmp_global_allow - Are we allowed to send one more ICMP message ?
   *
   * 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.
   * Note: called with BH disabled
   */
  bool icmp_global_allow(void)
  {
  	u32 credit, delta, incr = 0, now = (u32)jiffies;
  	bool rc = false;
  
  	/* Check if token bucket is empty and cannot be refilled
  	 * without taking the spinlock. The READ_ONCE() are paired
  	 * with the following WRITE_ONCE() in this same function.
  	 */
  	if (!READ_ONCE(icmp_global.credit)) {
  		delta = min_t(u32, now - READ_ONCE(icmp_global.stamp), HZ);
  		if (delta < HZ / 50)
  			return false;
  	}
  
  	spin_lock(&icmp_global.lock);
  	delta = min_t(u32, now - icmp_global.stamp, HZ);
  	if (delta >= HZ / 50) {
  		incr = sysctl_icmp_msgs_per_sec * delta / HZ ;
  		if (incr)
  			WRITE_ONCE(icmp_global.stamp, now);
  	}
  	credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst);
  	if (credit) {
  		/* We want to use a credit of one in average, but need to randomize
  		 * it for security reasons.
  		 */
  		credit = max_t(int, credit - prandom_u32_max(3), 0);
  		rc = true;
  	}
  	WRITE_ONCE(icmp_global.credit, credit);
  	spin_unlock(&icmp_global.lock);
  	return rc;
  }
  EXPORT_SYMBOL(icmp_global_allow);
  
  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) & net->ipv4.sysctl_icmp_ratemask))
  		return true;
  
  	return false;
  }
  
  static bool icmpv4_global_allow(struct net *net, int type, int code)
  {
  	if (icmpv4_mask_allow(net, type, code))
  		return true;
  
  	if (icmp_global_allow())
  		return true;
  
  	return false;
  }
  
  /*
   *	Send an ICMP frame.
   */
  
  static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
  			       struct flowi4 *fl4, int type, int code)
  {
  	struct dst_entry *dst = &rt->dst;
  	struct inet_peer *peer;
  	bool rc = true;
  	int vif;
  
  	if (icmpv4_mask_allow(net, type, code))
  		goto out;
  
  	/* No rate limit on loopback */
  	if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
  		goto out;
  
  	vif = l3mdev_master_ifindex(dst->dev);
  	peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1);
  	rc = inet_peer_xrlim_allow(peer, net->ipv4.sysctl_icmp_ratelimit);
  	if (peer)
  		inet_putpeer(peer);
  out:
  	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)
  {
  	struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
  	__wsum csum;
  
  	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_pointers[icmp_param->data.icmph.type].error)
  		nf_ct_attach(skb, icmp_param->skb);
  	return 0;
  }
  
  static void icmp_push_reply(struct icmp_bxm *icmp_param,
  			    struct flowi4 *fl4,
  			    struct ipcm_cookie *ipc, struct rtable **rt)
  {
  	struct sock *sk;
  	struct sk_buff *skb;
  
  	sk = icmp_sk(dev_net((*rt)->dst.dev));
  	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 ipcm_cookie ipc;
  	struct rtable *rt = skb_rtable(skb);
  	struct net *net = dev_net(rt->dst.dev);
  	struct flowi4 fl4;
  	struct sock *sk;
  	struct inet_sock *inet;
  	__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.opt, skb))
  		return;
  
  	/* Needed by both icmp_global_allow and icmp_xmit_lock */
  	local_bh_disable();
  
  	/* global icmp_msgs_per_sec */
  	if (!icmpv4_global_allow(net, type, code))
  		goto out_bh_enable;
  
  	sk = icmp_xmit_lock(net);
  	if (!sk)
  		goto out_bh_enable;
  	inet = inet_sk(sk);
  
  	icmp_param->data.icmph.checksum = 0;
  
  	ipcm_init(&ipc);
  	inet->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.opt.optlen) {
  		ipc.opt = &icmp_param->replyopts.opt;
  		if (ipc.opt->opt.srr)
  			daddr = icmp_param->replyopts.opt.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_tos = RT_TOS(ip_hdr(skb)->tos);
  	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))
  		icmp_push_reply(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 *route_lookup_dev = NULL;
  
  	if (skb->dev)
  		route_lookup_dev = skb->dev;
  	else if (skb_dst(skb))
  		route_lookup_dev = skb_dst(skb)->dev;
  	return route_lookup_dev;
  }
  
  static struct rtable *icmp_route_lookup(struct net *net,
  					struct flowi4 *fl4,
  					struct sk_buff *skb_in,
  					const struct iphdr *iph,
  					__be32 saddr, u8 tos, u32 mark,
  					int type, int code,
  					struct icmp_bxm *param)
  {
  	struct net_device *route_lookup_dev;
  	struct rtable *rt, *rt2;
  	struct flowi4 fl4_dec;
  	int err;
  
  	memset(fl4, 0, sizeof(*fl4));
  	fl4->daddr = (param->replyopts.opt.opt.srr ?
  		      param->replyopts.opt.opt.faddr : iph->saddr);
  	fl4->saddr = saddr;
  	fl4->flowi4_mark = mark;
  	fl4->flowi4_uid = sock_net_uid(net, NULL);
  	fl4->flowi4_tos = RT_TOS(tos);
  	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;
  
  	rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
  					   flowi4_to_flowi(fl4), NULL, 0);
  	if (!IS_ERR(rt)) {
  		if (rt != rt2)
  			return rt;
  	} else if (PTR_ERR(rt) == -EPERM) {
  		rt = NULL;
  	} else
  		return rt;
  
  	err = xfrm_decode_session_reverse(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 = {};
  		unsigned long orefdst;
  
  		fl4_2.daddr = fl4_dec.saddr;
  		rt2 = ip_route_output_key(net, &fl4_2);
  		if (IS_ERR(rt2)) {
  			err = PTR_ERR(rt2);
  			goto relookup_failed;
  		}
  		/* Ugh! */
  		orefdst = skb_in->_skb_refdst; /* save old refdst */
  		skb_dst_set(skb_in, NULL);
  		err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
  				     RT_TOS(tos), rt2->dst.dev);
  
  		dst_release(&rt2->dst);
  		rt2 = skb_rtable(skb_in);
  		skb_in->_skb_refdst = orefdst; /* restore old refdst */
  	}
  
  	if (err)
  		goto relookup_failed;
  
  	rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
  					    flowi4_to_flowi(&fl4_dec), NULL,
  					    XFRM_LOOKUP_ICMP);
  	if (!IS_ERR(rt2)) {
  		dst_release(&rt->dst);
  		memcpy(fl4, &fl4_dec, sizeof(*fl4));
  		rt = rt2;
  	} else if (PTR_ERR(rt2) == -EPERM) {
  		if (rt)
  			dst_release(&rt->dst);
  		return rt2;
  	} else {
  		err = PTR_ERR(rt2);
  		goto relookup_failed;
  	}
  	return rt;
  
  relookup_failed:
  	if (rt)
  		return rt;
  	return ERR_PTR(err);
  }
  
  /*
   *	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 ip_options *opt)
  {
  	struct iphdr *iph;
  	int room;
  	struct icmp_bxm icmp_param;
  	struct rtable *rt = skb_rtable(skb_in);
  	struct ipcm_cookie ipc;
  	struct flowi4 fl4;
  	__be32 saddr;
  	u8  tos;
  	u32 mark;
  	struct net *net;
  	struct sock *sk;
  
  	if (!rt)
  		goto out;
  
  	if (rt->dst.dev)
  		net = dev_net(rt->dst.dev);
  	else if (skb_in->dev)
  		net = dev_net(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 icmp_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))
  		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) &&
  		    net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
  			dev = dev_get_by_index_rcu(net, 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.opt, skb_in, 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);
  	inet_sk(sk)->tos = tos;
  	ipcm_init(&ipc);
  	ipc.addr = iph->saddr;
  	ipc.opt = &icmp_param.replyopts.opt;
  	ipc.sockc.mark = mark;
  
  	rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,
  			       type, code, &icmp_param);
  	if (IS_ERR(rt))
  		goto out_unlock;
  
  	/* peer icmp_ratelimit */
  	if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
  		goto ende;
  
  	/* RFC says return as much as we can without exceeding 576 bytes. */
  
  	room = dst_mtu(&rt->dst);
  	if (room > 576)
  		room = 576;
  	room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
  	room -= sizeof(struct icmphdr);
  
  	icmp_param.data_len = skb_in->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);
  
  	icmp_push_reply(&icmp_param, &fl4, &ipc, &rt);
  ende:
  	ip_rt_put(rt);
  out_unlock:
  	icmp_xmit_unlock(sk);
  out_bh_enable:
  	local_bh_enable();
  out:;
  }
  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;
  	struct ip_options opts = { 0 };
  	enum ip_conntrack_info ctinfo;
  	struct nf_conn *ct;
  	__be32 orig_ip;
  
  	ct = nf_ct_get(skb_in, &ctinfo);
  	if (!ct || !(ct->status & IPS_SRC_NAT)) {
  		__icmp_send(skb_in, type, code, info, &opts);
  		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;
  	ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
  	__icmp_send(skb_in, type, code, info, &opts);
  	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)) {
  		__ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
  		return;
  	}
  
  	raw_icmp_error(skb, protocol, info);
  
  	ipprot = rcu_dereference(inet_protos[protocol]);
  	if (ipprot && ipprot->err_handler)
  		ipprot->err_handler(skb, info);
  }
  
  static bool icmp_tag_validation(int proto)
  {
  	bool ok;
  
  	rcu_read_lock();
  	ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
  	rcu_read_unlock();
  	return ok;
  }
  
  /*
   *	Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
   *	ICMP_PARAMETERPROB.
   */
  
  static bool icmp_unreach(struct sk_buff *skb)
  {
  	const struct iphdr *iph;
  	struct icmphdr *icmph;
  	struct net *net;
  	u32 info = 0;
  
  	net = dev_net(skb_dst(skb)->dev);
  
  	/*
  	 *	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. */
  		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 (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 (!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 true;
  out_err:
  	__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
  	return false;
  }
  
  
  /*
   *	Handle ICMP_REDIRECT.
   */
  
  static bool icmp_redirect(struct sk_buff *skb)
  {
  	if (skb->len < sizeof(struct iphdr)) {
  		__ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
  		return false;
  	}
  
  	if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
  		/* there aught to be a stat */
  		return false;
  	}
  
  	icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
  	return true;
  }
  
  /*
   *	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 bool icmp_echo(struct sk_buff *skb)
  {
  	struct icmp_bxm icmp_param;
  	struct net *net;
  
  	net = dev_net(skb_dst(skb)->dev);
  	/* should there be an ICMP stat for ignored echos? */
  	if (net->ipv4.sysctl_icmp_echo_ignore_all)
  		return true;
  
  	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 true;
  
  	icmp_reply(&icmp_param, skb);
  	return true;
  }
  
  /*	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 icmp_ext_hdr *ext_hdr, _ext_hdr;
  	struct icmp_ext_echo_iio *iio, _iio;
  	struct net *net = dev_net(skb->dev);
  	struct net_device *dev;
  	char buff[IFNAMSIZ];
  	u16 ident_len;
  	u8 status;
  
  	if (!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_stub->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;
  	if (__in_dev_get_rcu(dev) && __in_dev_get_rcu(dev)->ifa_list)
  		status |= ICMP_EXT_ECHOREPLY_IPV4;
  	if (!list_empty(&rcu_dereference(dev->ip6_ptr)->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;
  }
  EXPORT_SYMBOL_GPL(icmp_build_probe);
  
  /*
   *	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 bool icmp_timestamp(struct sk_buff *skb)
  {
  	struct icmp_bxm icmp_param;
  	/*
  	 *	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 true;
  
  out_err:
  	__ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
  	return false;
  }
  
  static bool icmp_discard(struct sk_buff *skb)
  {
  	/* pretend it was a success */
  	return true;
  }
  
  /*
   *	Deal with incoming ICMP packets.
   */
  int icmp_rcv(struct sk_buff *skb)
  {
  	struct icmphdr *icmph;
  	struct rtable *rt = skb_rtable(skb);
  	struct net *net = dev_net(rt->dst.dev);
  	bool success;
  
  	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))
  			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))
  			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.
  		 */
  		success = icmp_echo(skb);
  		goto success_check;
  	}
  
  	if (icmph->type == ICMP_EXT_ECHOREPLY) {
  		success = ping_rcv(skb);
  		goto success_check;
  	}
  
  	/*
  	 *	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)
  		goto error;
  
  	/*
  	 *	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) &&
  		    net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
  			goto error;
  		}
  		if (icmph->type != ICMP_ECHO &&
  		    icmph->type != ICMP_TIMESTAMP &&
  		    icmph->type != ICMP_ADDRESS &&
  		    icmph->type != ICMP_ADDRESSREPLY) {
  			goto error;
  		}
  	}
  
  	success = icmp_pointers[icmph->type].handler(skb);
  success_check:
  	if (success)  {
  		consume_skb(skb);
  		return NET_RX_SUCCESS;
  	}
  
  drop:
  	kfree_skb(skb);
  	return NET_RX_DROP;
  csum_error:
  	__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;
  }
  EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
  
  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);
  	int type = icmp_hdr(skb)->type;
  	int code = icmp_hdr(skb)->code;
  	struct net *net = dev_net(skb->dev);
  
  	/*
  	 * 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 void __net_exit icmp_sk_exit(struct net *net)
  {
  	int i;
  
  	for_each_possible_cpu(i)
  		inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i));
  	free_percpu(net->ipv4.icmp_sk);
  	net->ipv4.icmp_sk = NULL;
  }
  
  static int __net_init icmp_sk_init(struct net *net)
  {
  	int i, err;
  
  	net->ipv4.icmp_sk = alloc_percpu(struct sock *);
  	if (!net->ipv4.icmp_sk)
  		return -ENOMEM;
  
  	for_each_possible_cpu(i) {
  		struct sock *sk;
  
  		err = inet_ctl_sock_create(&sk, PF_INET,
  					   SOCK_RAW, IPPROTO_ICMP, net);
  		if (err < 0)
  			goto fail;
  
  		*per_cpu_ptr(net->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;
  	}
  
  	/* 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;
  
  	return 0;
  
  fail:
  	icmp_sk_exit(net);
  	return err;
  }
  
  static struct pernet_operations __net_initdata icmp_sk_ops = {
         .init = icmp_sk_init,
         .exit = icmp_sk_exit,
  };
  
  int __init icmp_init(void)
  {
  	return register_pernet_subsys(&icmp_sk_ops);
  }
  