nf_conntrack_proto_icmp.c

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/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <[email protected]>
 *
 * 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 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));
}

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;
    u16 zone = tmpl ? nf_ct_zone(tmpl) : NF_CT_DEFAULT_ZONE;

    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, 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(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, tmpl, 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)
{
    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 defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
    .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,
};