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/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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#include <linux/types.h>
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#include <linux/timer.h>
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#include <linux/netfilter.h>
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#include <linux/icmp.h>
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#include <linux/seq_file.h>
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#include <net/checksum.h>
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#include <linux/netfilter_ipv4.h>
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#include <net/netfilter/nf_conntrack_tuple.h>
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#include <net/netfilter/nf_conntrack_l4proto.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/nf_conntrack_zones.h>
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#include <net/netfilter/nf_log.h>
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static unsigned int nf_ct_icmp_timeout __read_mostly = 30*HZ;
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static bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
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struct nf_conntrack_tuple *tuple)
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const struct icmphdr *hp;
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hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
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tuple->dst.u.icmp.type = hp->type;
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tuple->src.u.icmp.id = hp->un.echo.id;
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tuple->dst.u.icmp.code = hp->code;
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/* Add 1; spaces filled with 0. */
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static const u_int8_t invmap[] = {
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[ICMP_ECHO] = ICMP_ECHOREPLY + 1,
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[ICMP_ECHOREPLY] = ICMP_ECHO + 1,
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[ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
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[ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
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[ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
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[ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
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[ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
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[ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
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static bool icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
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const struct nf_conntrack_tuple *orig)
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if (orig->dst.u.icmp.type >= sizeof(invmap) ||
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!invmap[orig->dst.u.icmp.type])
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tuple->src.u.icmp.id = orig->src.u.icmp.id;
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tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
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tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
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/* Print out the per-protocol part of the tuple. */
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static int icmp_print_tuple(struct seq_file *s,
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const struct nf_conntrack_tuple *tuple)
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return seq_printf(s, "type=%u code=%u id=%u ",
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tuple->dst.u.icmp.type,
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tuple->dst.u.icmp.code,
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ntohs(tuple->src.u.icmp.id));
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/* Returns verdict for packet, or -1 for invalid. */
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static int icmp_packet(struct nf_conn *ct,
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const struct sk_buff *skb,
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enum ip_conntrack_info ctinfo,
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/* Do not immediately delete the connection after the first
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successful reply to avoid excessive conntrackd traffic
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and also to handle correctly ICMP echo reply duplicates. */
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nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
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/* Called when a new connection for this protocol found. */
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static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
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static const u_int8_t valid_new[] = {
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[ICMP_TIMESTAMP] = 1,
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[ICMP_INFO_REQUEST] = 1,
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if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
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!valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
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/* Can't create a new ICMP `conn' with this. */
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pr_debug("icmp: can't create new conn with type %u\n",
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ct->tuplehash[0].tuple.dst.u.icmp.type);
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nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
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/* Returns conntrack if it dealt with ICMP, and filled in skb fields */
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icmp_error_message(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
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enum ip_conntrack_info *ctinfo,
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unsigned int hooknum)
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struct nf_conntrack_tuple innertuple, origtuple;
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const struct nf_conntrack_l4proto *innerproto;
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const struct nf_conntrack_tuple_hash *h;
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u16 zone = tmpl ? nf_ct_zone(tmpl) : NF_CT_DEFAULT_ZONE;
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NF_CT_ASSERT(skb->nfct == NULL);
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/* Are they talking about one of our connections? */
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if (!nf_ct_get_tuplepr(skb,
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skb_network_offset(skb) + ip_hdrlen(skb)
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+ sizeof(struct icmphdr),
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PF_INET, &origtuple)) {
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pr_debug("icmp_error_message: failed to get tuple\n");
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/* rcu_read_lock()ed by nf_hook_slow */
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innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
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/* Ordinarily, we'd expect the inverted tupleproto, but it's
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been preserved inside the ICMP. */
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if (!nf_ct_invert_tuple(&innertuple, &origtuple,
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&nf_conntrack_l3proto_ipv4, innerproto)) {
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pr_debug("icmp_error_message: no match\n");
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*ctinfo = IP_CT_RELATED;
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h = nf_conntrack_find_get(net, zone, &innertuple);
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pr_debug("icmp_error_message: no match\n");
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if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
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*ctinfo += IP_CT_IS_REPLY;
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/* Update skb to refer to this connection */
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skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
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skb->nfctinfo = *ctinfo;
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/* Small and modified version of icmp_rcv */
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icmp_error(struct net *net, struct nf_conn *tmpl,
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struct sk_buff *skb, unsigned int dataoff,
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enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
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const struct icmphdr *icmph;
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/* Not enough header? */
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icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
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if (LOG_INVALID(net, IPPROTO_ICMP))
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nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
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"nf_ct_icmp: short packet ");
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/* See ip_conntrack_proto_tcp.c */
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if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
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nf_ip_checksum(skb, hooknum, dataoff, 0)) {
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if (LOG_INVALID(net, IPPROTO_ICMP))
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nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
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"nf_ct_icmp: bad HW ICMP checksum ");
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* 18 is the highest 'known' ICMP type. Anything else is a mystery
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* RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
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if (icmph->type > NR_ICMP_TYPES) {
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if (LOG_INVALID(net, IPPROTO_ICMP))
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nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
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"nf_ct_icmp: invalid ICMP type ");
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/* Need to track icmp error message? */
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if (icmph->type != ICMP_DEST_UNREACH &&
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icmph->type != ICMP_SOURCE_QUENCH &&
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icmph->type != ICMP_TIME_EXCEEDED &&
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icmph->type != ICMP_PARAMETERPROB &&
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icmph->type != ICMP_REDIRECT)
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return icmp_error_message(net, tmpl, skb, ctinfo, hooknum);
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#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
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#include <linux/netfilter/nfnetlink.h>
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#include <linux/netfilter/nfnetlink_conntrack.h>
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static int icmp_tuple_to_nlattr(struct sk_buff *skb,
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const struct nf_conntrack_tuple *t)
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NLA_PUT_BE16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id);
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NLA_PUT_U8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type);
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NLA_PUT_U8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code);
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static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
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[CTA_PROTO_ICMP_TYPE] = { .type = NLA_U8 },
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[CTA_PROTO_ICMP_CODE] = { .type = NLA_U8 },
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[CTA_PROTO_ICMP_ID] = { .type = NLA_U16 },
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static int icmp_nlattr_to_tuple(struct nlattr *tb[],
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struct nf_conntrack_tuple *tuple)
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if (!tb[CTA_PROTO_ICMP_TYPE] ||
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!tb[CTA_PROTO_ICMP_CODE] ||
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!tb[CTA_PROTO_ICMP_ID])
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tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
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tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
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tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
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if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
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!invmap[tuple->dst.u.icmp.type])
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static int icmp_nlattr_tuple_size(void)
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return nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
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static struct ctl_table_header *icmp_sysctl_header;
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static struct ctl_table icmp_sysctl_table[] = {
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.procname = "nf_conntrack_icmp_timeout",
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.data = &nf_ct_icmp_timeout,
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.maxlen = sizeof(unsigned int),
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.proc_handler = proc_dointvec_jiffies,
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#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
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static struct ctl_table icmp_compat_sysctl_table[] = {
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.procname = "ip_conntrack_icmp_timeout",
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.data = &nf_ct_icmp_timeout,
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.maxlen = sizeof(unsigned int),
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.proc_handler = proc_dointvec_jiffies,
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#endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
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#endif /* CONFIG_SYSCTL */
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struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
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.l4proto = IPPROTO_ICMP,
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.pkt_to_tuple = icmp_pkt_to_tuple,
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.invert_tuple = icmp_invert_tuple,
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.print_tuple = icmp_print_tuple,
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.packet = icmp_packet,
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#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
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.tuple_to_nlattr = icmp_tuple_to_nlattr,
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.nlattr_tuple_size = icmp_nlattr_tuple_size,
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.nlattr_to_tuple = icmp_nlattr_to_tuple,
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.nla_policy = icmp_nla_policy,
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.ctl_table_header = &icmp_sysctl_header,
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.ctl_table = icmp_sysctl_table,
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#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
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.ctl_compat_table = icmp_compat_sysctl_table,