// SPDX-License-Identifier: GPL-2.0-only
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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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* (C) 2006-2010 Patrick McHardy <kaber@trash.net>
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*/
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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/in.h>
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#include <linux/icmp.h>
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#include <linux/seq_file.h>
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#include <net/ip.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_timeout.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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#include "nf_internals.h"
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static const unsigned int nf_ct_icmp_timeout = 30*HZ;
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bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
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struct net *net, struct nf_conntrack_tuple *tuple)
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{
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const struct icmphdr *hp;
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struct icmphdr _hdr;
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hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
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if (hp == NULL)
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return false;
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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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return true;
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}
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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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};
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bool nf_conntrack_invert_icmp_tuple(struct nf_conntrack_tuple *tuple,
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const struct nf_conntrack_tuple *orig)
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{
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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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return false;
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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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return true;
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}
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/* Returns verdict for packet, or -1 for invalid. */
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int nf_conntrack_icmp_packet(struct nf_conn *ct,
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struct sk_buff *skb,
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enum ip_conntrack_info ctinfo,
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const struct nf_hook_state *state)
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{
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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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unsigned int *timeout = nf_ct_timeout_lookup(ct);
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static const u_int8_t valid_new[] = {
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[ICMP_ECHO] = 1,
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[ICMP_TIMESTAMP] = 1,
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[ICMP_INFO_REQUEST] = 1,
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[ICMP_ADDRESS] = 1
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};
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if (state->pf != NFPROTO_IPV4)
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return -NF_ACCEPT;
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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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return -NF_ACCEPT;
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}
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if (!timeout)
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timeout = &nf_icmp_pernet(nf_ct_net(ct))->timeout;
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nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
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return NF_ACCEPT;
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}
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/* Check inner header is related to any of the existing connections */
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int nf_conntrack_inet_error(struct nf_conn *tmpl, struct sk_buff *skb,
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unsigned int dataoff,
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const struct nf_hook_state *state,
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u8 l4proto, union nf_inet_addr *outer_daddr)
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{
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struct nf_conntrack_tuple innertuple, origtuple;
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const struct nf_conntrack_tuple_hash *h;
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const struct nf_conntrack_zone *zone;
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enum ip_conntrack_info ctinfo;
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struct nf_conntrack_zone tmp;
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union nf_inet_addr *ct_daddr;
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enum ip_conntrack_dir dir;
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struct nf_conn *ct;
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WARN_ON(skb_nfct(skb));
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zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
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/* Are they talking about one of our connections? */
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if (!nf_ct_get_tuplepr(skb, dataoff,
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state->pf, state->net, &origtuple))
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return -NF_ACCEPT;
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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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return -NF_ACCEPT;
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h = nf_conntrack_find_get(state->net, zone, &innertuple);
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if (!h)
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return -NF_ACCEPT;
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/* Consider: A -> T (=This machine) -> B
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* Conntrack entry will look like this:
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* Original: A->B
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* Reply: B->T (SNAT case) OR A
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*
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* When this function runs, we got packet that looks like this:
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* iphdr|icmphdr|inner_iphdr|l4header (tcp, udp, ..).
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*
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* Above nf_conntrack_find_get() makes lookup based on inner_hdr,
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* so we should expect that destination of the found connection
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* matches outer header destination address.
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*
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* In above example, we can consider these two cases:
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* 1. Error coming in reply direction from B or M (middle box) to
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* T (SNAT case) or A.
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* Inner saddr will be B, dst will be T or A.
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* The found conntrack will be reply tuple (B->T/A).
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* 2. Error coming in original direction from A or M to B.
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* Inner saddr will be A, inner daddr will be B.
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* The found conntrack will be original tuple (A->B).
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*
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* In both cases, conntrack[dir].dst == inner.dst.
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*
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* A bogus packet could look like this:
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* Inner: B->T
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* Outer: B->X (other machine reachable by T).
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*
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* In this case, lookup yields connection A->B and will
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* set packet from B->X as *RELATED*, even though no connection
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* from X was ever seen.
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*/
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ct = nf_ct_tuplehash_to_ctrack(h);
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dir = NF_CT_DIRECTION(h);
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ct_daddr = &ct->tuplehash[dir].tuple.dst.u3;
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if (!nf_inet_addr_cmp(outer_daddr, ct_daddr)) {
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if (state->pf == AF_INET) {
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nf_l4proto_log_invalid(skb, state->net, state->pf,
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l4proto,
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"outer daddr %pI4 != inner %pI4",
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&outer_daddr->ip, &ct_daddr->ip);
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} else if (state->pf == AF_INET6) {
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nf_l4proto_log_invalid(skb, state->net, state->pf,
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l4proto,
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"outer daddr %pI6 != inner %pI6",
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&outer_daddr->ip6, &ct_daddr->ip6);
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}
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nf_ct_put(ct);
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return -NF_ACCEPT;
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}
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ctinfo = IP_CT_RELATED;
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if (dir == 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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nf_ct_set(skb, ct, ctinfo);
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return NF_ACCEPT;
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}
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static void icmp_error_log(const struct sk_buff *skb,
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const struct nf_hook_state *state,
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const char *msg)
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{
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nf_l4proto_log_invalid(skb, state->net, state->pf,
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IPPROTO_ICMP, "%s", msg);
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}
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/* Small and modified version of icmp_rcv */
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int nf_conntrack_icmpv4_error(struct nf_conn *tmpl,
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struct sk_buff *skb, unsigned int dataoff,
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const struct nf_hook_state *state)
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{
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union nf_inet_addr outer_daddr;
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const struct icmphdr *icmph;
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struct icmphdr _ih;
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/* Not enough header? */
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icmph = skb_header_pointer(skb, dataoff, sizeof(_ih), &_ih);
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if (icmph == NULL) {
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icmp_error_log(skb, state, "short packet");
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return -NF_ACCEPT;
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}
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/* See nf_conntrack_proto_tcp.c */
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if (state->net->ct.sysctl_checksum &&
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state->hook == NF_INET_PRE_ROUTING &&
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nf_ip_checksum(skb, state->hook, dataoff, IPPROTO_ICMP)) {
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icmp_error_log(skb, state, "bad hw icmp checksum");
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return -NF_ACCEPT;
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}
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/*
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* 18 is the highest 'known' ICMP type. Anything else is a mystery
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*
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* RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
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* discarded.
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*/
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if (icmph->type > NR_ICMP_TYPES) {
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icmp_error_log(skb, state, "invalid icmp type");
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return -NF_ACCEPT;
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}
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/* Need to track icmp error message? */
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if (!icmp_is_err(icmph->type))
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return NF_ACCEPT;
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memset(&outer_daddr, 0, sizeof(outer_daddr));
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outer_daddr.ip = ip_hdr(skb)->daddr;
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dataoff += sizeof(*icmph);
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return nf_conntrack_inet_error(tmpl, skb, dataoff, state,
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IPPROTO_ICMP, &outer_daddr);
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}
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#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
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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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{
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if (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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goto nla_put_failure;
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return 0;
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nla_put_failure:
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return -1;
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}
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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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};
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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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u_int32_t flags)
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{
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if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_TYPE)) {
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if (!tb[CTA_PROTO_ICMP_TYPE])
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return -EINVAL;
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tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
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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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return -EINVAL;
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}
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if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_CODE)) {
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if (!tb[CTA_PROTO_ICMP_CODE])
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return -EINVAL;
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tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
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}
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if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_ID)) {
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if (!tb[CTA_PROTO_ICMP_ID])
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return -EINVAL;
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tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
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}
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return 0;
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}
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static unsigned int icmp_nlattr_tuple_size(void)
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{
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static unsigned int size __read_mostly;
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if (!size)
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size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
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return size;
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}
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#endif
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#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
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#include <linux/netfilter/nfnetlink.h>
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#include <linux/netfilter/nfnetlink_cttimeout.h>
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static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
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struct net *net, void *data)
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{
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unsigned int *timeout = data;
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struct nf_icmp_net *in = nf_icmp_pernet(net);
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if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
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if (!timeout)
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timeout = &in->timeout;
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*timeout =
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ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
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} else if (timeout) {
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/* Set default ICMP timeout. */
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*timeout = in->timeout;
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}
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return 0;
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}
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static int
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icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
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{
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const unsigned int *timeout = data;
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if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
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goto nla_put_failure;
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return 0;
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nla_put_failure:
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return -ENOSPC;
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}
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static const struct nla_policy
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icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
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[CTA_TIMEOUT_ICMP_TIMEOUT] = { .type = NLA_U32 },
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};
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#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
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void nf_conntrack_icmp_init_net(struct net *net)
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{
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struct nf_icmp_net *in = nf_icmp_pernet(net);
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in->timeout = nf_ct_icmp_timeout;
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}
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const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
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{
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.l4proto = IPPROTO_ICMP,
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#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
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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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#endif
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#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
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.ctnl_timeout = {
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.nlattr_to_obj = icmp_timeout_nlattr_to_obj,
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.obj_to_nlattr = icmp_timeout_obj_to_nlattr,
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.nlattr_max = CTA_TIMEOUT_ICMP_MAX,
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.obj_size = sizeof(unsigned int),
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.nla_policy = icmp_timeout_nla_policy,
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},
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#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
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};
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