text: /* (C) 1999-2001 Paul `Rusty' Russell
   * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   * (C) 2006-2010 Patrick McHardy <kaber@trash.net>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #include <linux/types.h>
  #include <linux/timer.h>
  #include <linux/netfilter.h>
  #include <linux/in.h>
  #include <linux/icmp.h>
  #include <linux/seq_file.h>
  #include <net/ip.h>
  #include <net/checksum.h>
  #include <linux/netfilter_ipv4.h>
  #include <net/netfilter/nf_conntrack_tuple.h>
  #include <net/netfilter/nf_conntrack_l4proto.h>
  #include <net/netfilter/nf_conntrack_core.h>
  #include <net/netfilter/nf_conntrack_zones.h>
  #include <net/netfilter/nf_log.h>
  
  static unsigned int nf_ct_icmp_timeout __read_mostly = 30*HZ;
  
  static inline struct nf_icmp_net *icmp_pernet(struct net *net)
  {
  	return &net->ct.nf_ct_proto.icmp;
  }
  
  static bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
  			      struct nf_conntrack_tuple *tuple)
  {
  	const struct icmphdr *hp;
  	struct icmphdr _hdr;
  
  	hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  	if (hp == NULL)
  		return false;
  
  	tuple->dst.u.icmp.type = hp->type;
  	tuple->src.u.icmp.id = hp->un.echo.id;
  	tuple->dst.u.icmp.code = hp->code;
  
  	return true;
  }
  
  /* Add 1; spaces filled with 0. */
  static const u_int8_t invmap[] = {
  	[ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  	[ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  	[ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  	[ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  	[ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  	[ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  	[ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  	[ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
  };
  
  static bool icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
  			      const struct nf_conntrack_tuple *orig)
  {
  	if (orig->dst.u.icmp.type >= sizeof(invmap) ||
  	    !invmap[orig->dst.u.icmp.type])
  		return false;
  
  	tuple->src.u.icmp.id = orig->src.u.icmp.id;
  	tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  	tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  	return true;
  }
  
  /* Print out the per-protocol part of the tuple. */
  static void icmp_print_tuple(struct seq_file *s,
  			    const struct nf_conntrack_tuple *tuple)
  {
  	seq_printf(s, "type=%u code=%u id=%u ",
  		   tuple->dst.u.icmp.type,
  		   tuple->dst.u.icmp.code,
  		   ntohs(tuple->src.u.icmp.id));
  }
  
  static unsigned int *icmp_get_timeouts(struct net *net)
  {
  	return &icmp_pernet(net)->timeout;
  }
  
  /* Returns verdict for packet, or -1 for invalid. */
  static int icmp_packet(struct nf_conn *ct,
  		       const struct sk_buff *skb,
  		       unsigned int dataoff,
  		       enum ip_conntrack_info ctinfo,
  		       u_int8_t pf,
  		       unsigned int hooknum,
  		       unsigned int *timeout)
  {
  	/* Do not immediately delete the connection after the first
  	   successful reply to avoid excessive conntrackd traffic
  	   and also to handle correctly ICMP echo reply duplicates. */
  	nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
  
  	return NF_ACCEPT;
  }
  
  /* Called when a new connection for this protocol found. */
  static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
  		     unsigned int dataoff, unsigned int *timeouts)
  {
  	static const u_int8_t valid_new[] = {
  		[ICMP_ECHO] = 1,
  		[ICMP_TIMESTAMP] = 1,
  		[ICMP_INFO_REQUEST] = 1,
  		[ICMP_ADDRESS] = 1
  	};
  
  	if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
  	    !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
  		/* Can't create a new ICMP `conn' with this. */
  		pr_debug("icmp: can't create new conn with type %u\n",
  			 ct->tuplehash[0].tuple.dst.u.icmp.type);
  		nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
  		return false;
  	}
  	return true;
  }
  
  /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
  static int
  icmp_error_message(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
  		 enum ip_conntrack_info *ctinfo,
  		 unsigned int hooknum)
  {
  	struct nf_conntrack_tuple innertuple, origtuple;
  	const struct nf_conntrack_l4proto *innerproto;
  	const struct nf_conntrack_tuple_hash *h;
  	const struct nf_conntrack_zone *zone;
  	struct nf_conntrack_zone tmp;
  
  	NF_CT_ASSERT(skb->nfct == NULL);
  	zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
  
  	/* Are they talking about one of our connections? */
  	if (!nf_ct_get_tuplepr(skb,
  			       skb_network_offset(skb) + ip_hdrlen(skb)
  						       + sizeof(struct icmphdr),
  			       PF_INET, &origtuple)) {
  		pr_debug("icmp_error_message: failed to get tuple\n");
  		return -NF_ACCEPT;
  	}
  
  	/* rcu_read_lock()ed by nf_hook_slow */
  	innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
  
  	/* Ordinarily, we'd expect the inverted tupleproto, but it's
  	   been preserved inside the ICMP. */
  	if (!nf_ct_invert_tuple(&innertuple, &origtuple,
  				&nf_conntrack_l3proto_ipv4, innerproto)) {
  		pr_debug("icmp_error_message: no match\n");
  		return -NF_ACCEPT;
  	}
  
  	*ctinfo = IP_CT_RELATED;
  
  	h = nf_conntrack_find_get(net, zone, &innertuple);
  	if (!h) {
  		pr_debug("icmp_error_message: no match\n");
  		return -NF_ACCEPT;
  	}
  
  	if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
  		*ctinfo += IP_CT_IS_REPLY;
  
  	/* Update skb to refer to this connection */
  	skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
  	skb->nfctinfo = *ctinfo;
  	return NF_ACCEPT;
  }
  
  /* Small and modified version of icmp_rcv */
  static int
  icmp_error(struct net *net, struct nf_conn *tmpl,
  	   struct sk_buff *skb, unsigned int dataoff,
  	   enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
  {
  	const struct icmphdr *icmph;
  	struct icmphdr _ih;
  
  	/* Not enough header? */
  	icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
  	if (icmph == NULL) {
  		if (LOG_INVALID(net, IPPROTO_ICMP))
  			nf_log_packet(net, PF_INET, 0, skb, NULL, NULL,
  				      NULL, "nf_ct_icmp: short packet ");
  		return -NF_ACCEPT;
  	}
  
  	/* See ip_conntrack_proto_tcp.c */
  	if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
  	    nf_ip_checksum(skb, hooknum, dataoff, 0)) {
  		if (LOG_INVALID(net, IPPROTO_ICMP))
  			nf_log_packet(net, PF_INET, 0, skb, NULL, NULL, NULL,
  				      "nf_ct_icmp: bad HW ICMP checksum ");
  		return -NF_ACCEPT;
  	}
  
  	/*
  	 *	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) {
  		if (LOG_INVALID(net, IPPROTO_ICMP))
  			nf_log_packet(net, PF_INET, 0, skb, NULL, NULL, NULL,
  				      "nf_ct_icmp: invalid ICMP type ");
  		return -NF_ACCEPT;
  	}
  
  	/* Need to track icmp error message? */
  	if (icmph->type != ICMP_DEST_UNREACH &&
  	    icmph->type != ICMP_SOURCE_QUENCH &&
  	    icmph->type != ICMP_TIME_EXCEEDED &&
  	    icmph->type != ICMP_PARAMETERPROB &&
  	    icmph->type != ICMP_REDIRECT)
  		return NF_ACCEPT;
  
  	return icmp_error_message(net, tmpl, skb, ctinfo, hooknum);
  }
  
  #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
  
  #include <linux/netfilter/nfnetlink.h>
  #include <linux/netfilter/nfnetlink_conntrack.h>
  
  static int icmp_tuple_to_nlattr(struct sk_buff *skb,
  				const struct nf_conntrack_tuple *t)
  {
  	if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
  	    nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
  	    nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code))
  		goto nla_put_failure;
  	return 0;
  
  nla_put_failure:
  	return -1;
  }
  
  static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
  	[CTA_PROTO_ICMP_TYPE]	= { .type = NLA_U8 },
  	[CTA_PROTO_ICMP_CODE]	= { .type = NLA_U8 },
  	[CTA_PROTO_ICMP_ID]	= { .type = NLA_U16 },
  };
  
  static int icmp_nlattr_to_tuple(struct nlattr *tb[],
  				struct nf_conntrack_tuple *tuple)
  {
  	if (!tb[CTA_PROTO_ICMP_TYPE] ||
  	    !tb[CTA_PROTO_ICMP_CODE] ||
  	    !tb[CTA_PROTO_ICMP_ID])
  		return -EINVAL;
  
  	tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
  	tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
  	tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
  
  	if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
  	    !invmap[tuple->dst.u.icmp.type])
  		return -EINVAL;
  
  	return 0;
  }
  
  static int icmp_nlattr_tuple_size(void)
  {
  	return nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
  }
  #endif
  
  #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
  
  #include <linux/netfilter/nfnetlink.h>
  #include <linux/netfilter/nfnetlink_cttimeout.h>
  
  static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
  				      struct net *net, void *data)
  {
  	unsigned int *timeout = data;
  	struct nf_icmp_net *in = icmp_pernet(net);
  
  	if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
  		*timeout =
  			ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
  	} else {
  		/* Set default ICMP timeout. */
  		*timeout = in->timeout;
  	}
  	return 0;
  }
  
  static int
  icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
  {
  	const unsigned int *timeout = data;
  
  	if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
  		goto nla_put_failure;
  	return 0;
  
  nla_put_failure:
  	return -ENOSPC;
  }
  
  static const struct nla_policy
  icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
  	[CTA_TIMEOUT_ICMP_TIMEOUT]	= { .type = NLA_U32 },
  };
  #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
  
  #ifdef CONFIG_SYSCTL
  static struct ctl_table icmp_sysctl_table[] = {
  	{
  		.procname	= "nf_conntrack_icmp_timeout",
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_jiffies,
  	},
  	{ }
  };
  #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
  static struct ctl_table icmp_compat_sysctl_table[] = {
  	{
  		.procname	= "ip_conntrack_icmp_timeout",
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_jiffies,
  	},
  	{ }
  };
  #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
  #endif /* CONFIG_SYSCTL */
  
  static int icmp_kmemdup_sysctl_table(struct nf_proto_net *pn,
  				     struct nf_icmp_net *in)
  {
  #ifdef CONFIG_SYSCTL
  	pn->ctl_table = kmemdup(icmp_sysctl_table,
  				sizeof(icmp_sysctl_table),
  				GFP_KERNEL);
  	if (!pn->ctl_table)
  		return -ENOMEM;
  
  	pn->ctl_table[0].data = &in->timeout;
  #endif
  	return 0;
  }
  
  static int icmp_kmemdup_compat_sysctl_table(struct nf_proto_net *pn,
  					    struct nf_icmp_net *in)
  {
  #ifdef CONFIG_SYSCTL
  #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
  	pn->ctl_compat_table = kmemdup(icmp_compat_sysctl_table,
  				       sizeof(icmp_compat_sysctl_table),
  				       GFP_KERNEL);
  	if (!pn->ctl_compat_table)
  		return -ENOMEM;
  
  	pn->ctl_compat_table[0].data = &in->timeout;
  #endif
  #endif
  	return 0;
  }
  
  static int icmp_init_net(struct net *net, u_int16_t proto)
  {
  	int ret;
  	struct nf_icmp_net *in = icmp_pernet(net);
  	struct nf_proto_net *pn = &in->pn;
  
  	in->timeout = nf_ct_icmp_timeout;
  
  	ret = icmp_kmemdup_compat_sysctl_table(pn, in);
  	if (ret < 0)
  		return ret;
  
  	ret = icmp_kmemdup_sysctl_table(pn, in);
  	if (ret < 0)
  		nf_ct_kfree_compat_sysctl_table(pn);
  
  	return ret;
  }
  
  static struct nf_proto_net *icmp_get_net_proto(struct net *net)
  {
  	return &net->ct.nf_ct_proto.icmp.pn;
  }
  
  struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
  {
  	.l3proto		= PF_INET,
  	.l4proto		= IPPROTO_ICMP,
  	.name			= "icmp",
  	.pkt_to_tuple		= icmp_pkt_to_tuple,
  	.invert_tuple		= icmp_invert_tuple,
  	.print_tuple		= icmp_print_tuple,
  	.packet			= icmp_packet,
  	.get_timeouts		= icmp_get_timeouts,
  	.new			= icmp_new,
  	.error			= icmp_error,
  	.destroy		= NULL,
  	.me			= NULL,
  #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
  	.tuple_to_nlattr	= icmp_tuple_to_nlattr,
  	.nlattr_tuple_size	= icmp_nlattr_tuple_size,
  	.nlattr_to_tuple	= icmp_nlattr_to_tuple,
  	.nla_policy		= icmp_nla_policy,
  #endif
  #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
  	.ctnl_timeout		= {
  		.nlattr_to_obj	= icmp_timeout_nlattr_to_obj,
  		.obj_to_nlattr	= icmp_timeout_obj_to_nlattr,
  		.nlattr_max	= CTA_TIMEOUT_ICMP_MAX,
  		.obj_size	= sizeof(unsigned int),
  		.nla_policy	= icmp_timeout_nla_policy,
  	},
  #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
  	.init_net		= icmp_init_net,
  	.get_net_proto		= icmp_get_net_proto,
  };
  