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root/net/ipv4/netfilter/nf_conntrack_proto_icmp.c

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DEFINITIONS

This source file includes following definitions.
  1. icmp_pkt_to_tuple
  2. icmp_invert_tuple
  3. icmp_print_tuple
  4. icmp_packet
  5. icmp_new
  6. icmp_error_message
  7. icmp_error
  8. icmp_tuple_to_nlattr
  9. icmp_nlattr_to_tuple

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 *
 * 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_log.h>

static unsigned long nf_ct_icmp_timeout __read_mostly = 30*HZ;

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 int icmp_print_tuple(struct seq_file *s,
                            const struct nf_conntrack_tuple *tuple)
{
        return 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));
}

/* 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)
{
        /* Try to delete connection immediately after all replies:
           won't actually vanish as we still have skb, and del_timer
           means this will only run once even if count hits zero twice
           (theoretically possible with SMP) */
        if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
                if (atomic_dec_and_test(&ct->proto.icmp.count))
                        nf_ct_kill_acct(ct, ctinfo, skb);
        } else {
                atomic_inc(&ct->proto.icmp.count);
                nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, ct);
                nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_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)
{
        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;
        }
        atomic_set(&ct->proto.icmp.count, 0);
        return true;
}

/* Returns conntrack if it dealt with ICMP, and filled in skb fields */
static int
icmp_error_message(struct net *net, 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;

        NF_CT_ASSERT(skb->nfct == NULL);

        /* 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, &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 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(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(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(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, skb, ctinfo, hooknum);
}

#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)

#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)
{
        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);

        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;
}
#endif

#ifdef CONFIG_SYSCTL
static struct ctl_table_header *icmp_sysctl_header;
static struct ctl_table icmp_sysctl_table[] = {
        {
                .procname       = "nf_conntrack_icmp_timeout",
                .data           = &nf_ct_icmp_timeout,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec_jiffies,
        },
        {
                .ctl_name = 0
        }
};
#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
static struct ctl_table icmp_compat_sysctl_table[] = {
        {
                .procname       = "ip_conntrack_icmp_timeout",
                .data           = &nf_ct_icmp_timeout,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec_jiffies,
        },
        {
                .ctl_name = 0
        }
};
#endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
#endif /* CONFIG_SYSCTL */

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,
        .new                    = icmp_new,
        .error                  = icmp_error,
        .destroy                = NULL,
        .me                     = NULL,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
        .tuple_to_nlattr        = icmp_tuple_to_nlattr,
        .nlattr_to_tuple        = icmp_nlattr_to_tuple,
        .nla_policy             = icmp_nla_policy,
#endif
#ifdef CONFIG_SYSCTL
        .ctl_table_header       = &icmp_sysctl_header,
        .ctl_table              = icmp_sysctl_table,
#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
        .ctl_compat_table       = icmp_compat_sysctl_table,
#endif
#endif
};

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