Logo Search packages:      
Sourcecode: linux version File versions  Download package

icmp.c

/*
 *    NET3: Implementation of the ICMP protocol layer.
 *
 *          Alan Cox, <alan@redhat.com>
 *
 *    Version: $Id: icmp.c,v 1.85 2002/02/01 22:01:03 davem Exp $
 *
 *    This program is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU General Public License
 *    as published by the Free Software Foundation; either version
 *    2 of the License, or (at your option) any later version.
 *
 *    Some of the function names and the icmp unreach table for this
 *    module were derived from [icmp.c 1.0.11 06/02/93] by
 *    Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
 *    Other than that this module is a complete rewrite.
 *
 *    Fixes:
 *    Clemens Fruhwirth :     introduce global icmp rate limiting
 *                            with icmp type masking ability instead
 *                            of broken per type icmp timeouts.
 *          Mike Shaver :     RFC1122 checks.
 *          Alan Cox    :     Multicast ping reply as self.
 *          Alan Cox    :     Fix atomicity lockup in ip_build_xmit
 *                            call.
 *          Alan Cox    :     Added 216,128 byte paths to the MTU
 *                            code.
 *          Martin Mares      :     RFC1812 checks.
 *          Martin Mares      :     Can be configured to follow redirects
 *                            if acting as a router _without_ a
 *                            routing protocol (RFC 1812).
 *          Martin Mares      :     Echo requests may be configured to
 *                            be ignored (RFC 1812).
 *          Martin Mares      :     Limitation of ICMP error message
 *                            transmit rate (RFC 1812).
 *          Martin Mares      :     TOS and Precedence set correctly
 *                            (RFC 1812).
 *          Martin Mares      :     Now copying as much data from the
 *                            original packet as we can without
 *                            exceeding 576 bytes (RFC 1812).
 *    Willy Konynenberg :     Transparent proxying support.
 *          Keith Owens :     RFC1191 correction for 4.2BSD based
 *                            path MTU bug.
 *          Thomas Quinot     :     ICMP Dest Unreach codes up to 15 are
 *                            valid (RFC 1812).
 *          Andi Kleen  :     Check all packet lengths properly
 *                            and moved all kfree_skb() up to
 *                            icmp_rcv.
 *          Andi Kleen  :     Move the rate limit bookkeeping
 *                            into the dest entry and use a token
 *                            bucket filter (thanks to ANK). Make
 *                            the rates sysctl configurable.
 *          Yu Tianli   :     Fixed two ugly bugs in icmp_send
 *                            - IP option length was accounted wrongly
 *                            - ICMP header length was not accounted
 *                              at all.
 *              Tristan Greaves :       Added sysctl option to ignore bogus
 *                            broadcast responses from broken routers.
 *
 * To Fix:
 *
 *    - Should use skb_pull() instead of all the manual checking.
 *      This would also greatly simply some upper layer error handlers. --AK
 *
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/string.h>
#include <linux/netfilter_ipv4.h>
#include <net/snmp.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/protocol.h>
#include <net/icmp.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/raw.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <net/checksum.h>

/*
 *    Build xmit assembly blocks
 */

struct icmp_bxm {
      struct sk_buff *skb;
      int offset;
      int data_len;

      struct {
            struct icmphdr icmph;
            __be32             times[3];
      } data;
      int head_len;
      struct ip_options replyopts;
      unsigned char  optbuf[40];
};

/*
 *    Statistics
 */
DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics) __read_mostly;
DEFINE_SNMP_STAT(struct icmpmsg_mib, icmpmsg_statistics) __read_mostly;

/* An array of errno for error messages from dest unreach. */
/* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */

struct icmp_err icmp_err_convert[] = {
      {
            .errno = ENETUNREACH,   /* ICMP_NET_UNREACH */
            .fatal = 0,
      },
      {
            .errno = EHOSTUNREACH,  /* ICMP_HOST_UNREACH */
            .fatal = 0,
      },
      {
            .errno = ENOPROTOOPT    /* ICMP_PROT_UNREACH */,
            .fatal = 1,
      },
      {
            .errno = ECONNREFUSED,  /* ICMP_PORT_UNREACH */
            .fatal = 1,
      },
      {
            .errno = EMSGSIZE,      /* ICMP_FRAG_NEEDED */
            .fatal = 0,
      },
      {
            .errno = EOPNOTSUPP,    /* ICMP_SR_FAILED */
            .fatal = 0,
      },
      {
            .errno = ENETUNREACH,   /* ICMP_NET_UNKNOWN */
            .fatal = 1,
      },
      {
            .errno = EHOSTDOWN,     /* ICMP_HOST_UNKNOWN */
            .fatal = 1,
      },
      {
            .errno = ENONET,  /* ICMP_HOST_ISOLATED */
            .fatal = 1,
      },
      {
            .errno = ENETUNREACH,   /* ICMP_NET_ANO   */
            .fatal = 1,
      },
      {
            .errno = EHOSTUNREACH,  /* ICMP_HOST_ANO */
            .fatal = 1,
      },
      {
            .errno = ENETUNREACH,   /* ICMP_NET_UNR_TOS */
            .fatal = 0,
      },
      {
            .errno = EHOSTUNREACH,  /* ICMP_HOST_UNR_TOS */
            .fatal = 0,
      },
      {
            .errno = EHOSTUNREACH,  /* ICMP_PKT_FILTERED */
            .fatal = 1,
      },
      {
            .errno = EHOSTUNREACH,  /* ICMP_PREC_VIOLATION */
            .fatal = 1,
      },
      {
            .errno = EHOSTUNREACH,  /* ICMP_PREC_CUTOFF */
            .fatal = 1,
      },
};

/* Control parameters for ECHO replies. */
int sysctl_icmp_echo_ignore_all __read_mostly;
int sysctl_icmp_echo_ignore_broadcasts __read_mostly = 1;

/* Control parameter - ignore bogus broadcast responses? */
int sysctl_icmp_ignore_bogus_error_responses __read_mostly = 1;

/*
 *    Configurable global rate limit.
 *
 *    ratelimit defines tokens/packet consumed for dst->rate_token bucket
 *    ratemask defines which icmp types are ratelimited by setting
 *    it's bit position.
 *
 *    default:
 *    dest unreachable (3), source quench (4),
 *    time exceeded (11), parameter problem (12)
 */

int sysctl_icmp_ratelimit __read_mostly = 1 * HZ;
int sysctl_icmp_ratemask __read_mostly = 0x1818;
int sysctl_icmp_errors_use_inbound_ifaddr __read_mostly;

/*
 *    ICMP control array. This specifies what to do with each ICMP.
 */

struct icmp_control {
      void (*handler)(struct sk_buff *skb);
      short   error;          /* This ICMP is classed as an error message */
};

static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];

/*
 *    The ICMP socket(s). This is the most convenient way to flow control
 *    our ICMP output as well as maintain a clean interface throughout
 *    all layers. All Socketless IP sends will soon be gone.
 *
 *    On SMP we have one ICMP socket per-cpu.
 */
static DEFINE_PER_CPU(struct socket *, __icmp_socket) = NULL;
#define icmp_socket     __get_cpu_var(__icmp_socket)

static __inline__ int icmp_xmit_lock(void)
{
      local_bh_disable();

      if (unlikely(!spin_trylock(&icmp_socket->sk->sk_lock.slock))) {
            /* This can happen if the output path signals a
             * dst_link_failure() for an outgoing ICMP packet.
             */
            local_bh_enable();
            return 1;
      }
      return 0;
}

static void icmp_xmit_unlock(void)
{
      spin_unlock_bh(&icmp_socket->sk->sk_lock.slock);
}

/*
 *    Send an ICMP frame.
 */

/*
 *    Check transmit rate limitation for given message.
 *    The rate information is held in the destination cache now.
 *    This function is generic and could be used for other purposes
 *    too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
 *
 *    Note that the same dst_entry fields are modified by functions in
 *    route.c too, but these work for packet destinations while xrlim_allow
 *    works for icmp destinations. This means the rate limiting information
 *    for one "ip object" is shared - and these ICMPs are twice limited:
 *    by source and by destination.
 *
 *    RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
 *                  SHOULD allow setting of rate limits
 *
 *    Shared between ICMPv4 and ICMPv6.
 */
#define XRLIM_BURST_FACTOR 6
int xrlim_allow(struct dst_entry *dst, int timeout)
{
      unsigned long now;
      int rc = 0;

      now = jiffies;
      dst->rate_tokens += now - dst->rate_last;
      dst->rate_last = now;
      if (dst->rate_tokens > XRLIM_BURST_FACTOR * timeout)
            dst->rate_tokens = XRLIM_BURST_FACTOR * timeout;
      if (dst->rate_tokens >= timeout) {
            dst->rate_tokens -= timeout;
            rc = 1;
      }
      return rc;
}

static inline int icmpv4_xrlim_allow(struct rtable *rt, int type, int code)
{
      struct dst_entry *dst = &rt->u.dst;
      int rc = 1;

      if (type > NR_ICMP_TYPES)
            goto out;

      /* Don't limit PMTU discovery. */
      if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
            goto out;

      /* No rate limit on loopback */
      if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
            goto out;

      /* Limit if icmp type is enabled in ratemask. */
      if ((1 << type) & sysctl_icmp_ratemask)
            rc = xrlim_allow(dst, sysctl_icmp_ratelimit);
out:
      return rc;
}

/*
 *    Maintain the counters used in the SNMP statistics for outgoing ICMP
 */
void icmp_out_count(unsigned char type)
{
      ICMPMSGOUT_INC_STATS(type);
      ICMP_INC_STATS(ICMP_MIB_OUTMSGS);
}

/*
 *    Checksum each fragment, and on the first include the headers and final
 *    checksum.
 */
static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
                    struct sk_buff *skb)
{
      struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
      __wsum csum;

      csum = skb_copy_and_csum_bits(icmp_param->skb,
                              icmp_param->offset + offset,
                              to, len, 0);

      skb->csum = csum_block_add(skb->csum, csum, odd);
      if (icmp_pointers[icmp_param->data.icmph.type].error)
            nf_ct_attach(skb, icmp_param->skb);
      return 0;
}

static void icmp_push_reply(struct icmp_bxm *icmp_param,
                      struct ipcm_cookie *ipc, struct rtable *rt)
{
      struct sk_buff *skb;

      if (ip_append_data(icmp_socket->sk, icmp_glue_bits, icmp_param,
                     icmp_param->data_len+icmp_param->head_len,
                     icmp_param->head_len,
                     ipc, rt, MSG_DONTWAIT) < 0)
            ip_flush_pending_frames(icmp_socket->sk);
      else if ((skb = skb_peek(&icmp_socket->sk->sk_write_queue)) != NULL) {
            struct icmphdr *icmph = icmp_hdr(skb);
            __wsum csum = 0;
            struct sk_buff *skb1;

            skb_queue_walk(&icmp_socket->sk->sk_write_queue, skb1) {
                  csum = csum_add(csum, skb1->csum);
            }
            csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
                                     (char *)icmph,
                                     icmp_param->head_len, csum);
            icmph->checksum = csum_fold(csum);
            skb->ip_summed = CHECKSUM_NONE;
            ip_push_pending_frames(icmp_socket->sk);
      }
}

/*
 *    Driving logic for building and sending ICMP messages.
 */

static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
{
      struct sock *sk = icmp_socket->sk;
      struct inet_sock *inet = inet_sk(sk);
      struct ipcm_cookie ipc;
      struct rtable *rt = (struct rtable *)skb->dst;
      __be32 daddr;

      if (ip_options_echo(&icmp_param->replyopts, skb))
            return;

      if (icmp_xmit_lock())
            return;

      icmp_param->data.icmph.checksum = 0;

      inet->tos = ip_hdr(skb)->tos;
      daddr = ipc.addr = rt->rt_src;
      ipc.opt = NULL;
      if (icmp_param->replyopts.optlen) {
            ipc.opt = &icmp_param->replyopts;
            if (ipc.opt->srr)
                  daddr = icmp_param->replyopts.faddr;
      }
      {
            struct flowi fl = { .nl_u = { .ip4_u =
                                    { .daddr = daddr,
                                    .saddr = rt->rt_spec_dst,
                                    .tos = RT_TOS(ip_hdr(skb)->tos) } },
                            .proto = IPPROTO_ICMP };
            security_skb_classify_flow(skb, &fl);
            if (ip_route_output_key(&rt, &fl))
                  goto out_unlock;
      }
      if (icmpv4_xrlim_allow(rt, icmp_param->data.icmph.type,
                         icmp_param->data.icmph.code))
            icmp_push_reply(icmp_param, &ipc, rt);
      ip_rt_put(rt);
out_unlock:
      icmp_xmit_unlock();
}


/*
 *    Send an ICMP message in response to a situation
 *
 *    RFC 1122: 3.2.2   MUST send at least the IP header and 8 bytes of header.
 *            MAY send more (we do).
 *                MUST NOT change this header information.
 *                MUST NOT reply to a multicast/broadcast IP address.
 *                MUST NOT reply to a multicast/broadcast MAC address.
 *                MUST reply to only the first fragment.
 */

void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
{
      struct iphdr *iph;
      int room;
      struct icmp_bxm icmp_param;
      struct rtable *rt = (struct rtable *)skb_in->dst;
      struct ipcm_cookie ipc;
      __be32 saddr;
      u8  tos;

      if (!rt)
            goto out;

      /*
       *    Find the original header. It is expected to be valid, of course.
       *    Check this, icmp_send is called from the most obscure devices
       *    sometimes.
       */
      iph = ip_hdr(skb_in);

      if ((u8 *)iph < skb_in->head ||
          (skb_in->network_header + sizeof(*iph)) > skb_in->tail)
            goto out;

      /*
       *    No replies to physical multicast/broadcast
       */
      if (skb_in->pkt_type != PACKET_HOST)
            goto out;

      /*
       *    Now check at the protocol level
       */
      if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
            goto out;

      /*
       *    Only reply to fragment 0. We byte re-order the constant
       *    mask for efficiency.
       */
      if (iph->frag_off & htons(IP_OFFSET))
            goto out;

      /*
       *    If we send an ICMP error to an ICMP error a mess would result..
       */
      if (icmp_pointers[type].error) {
            /*
             *    We are an error, check if we are replying to an
             *    ICMP error
             */
            if (iph->protocol == IPPROTO_ICMP) {
                  u8 _inner_type, *itp;

                  itp = skb_header_pointer(skb_in,
                                     skb_network_header(skb_in) +
                                     (iph->ihl << 2) +
                                     offsetof(struct icmphdr,
                                            type) -
                                     skb_in->data,
                                     sizeof(_inner_type),
                                     &_inner_type);
                  if (itp == NULL)
                        goto out;

                  /*
                   *    Assume any unknown ICMP type is an error. This
                   *    isn't specified by the RFC, but think about it..
                   */
                  if (*itp > NR_ICMP_TYPES ||
                      icmp_pointers[*itp].error)
                        goto out;
            }
      }

      if (icmp_xmit_lock())
            return;

      /*
       *    Construct source address and options.
       */

      saddr = iph->daddr;
      if (!(rt->rt_flags & RTCF_LOCAL)) {
            struct net_device *dev = NULL;

            if (rt->fl.iif && sysctl_icmp_errors_use_inbound_ifaddr)
                  dev = dev_get_by_index(&init_net, rt->fl.iif);

            if (dev) {
                  saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
                  dev_put(dev);
            } else
                  saddr = 0;
      }

      tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
                                 IPTOS_PREC_INTERNETCONTROL) :
                                iph->tos;

      if (ip_options_echo(&icmp_param.replyopts, skb_in))
            goto out_unlock;


      /*
       *    Prepare data for ICMP header.
       */

      icmp_param.data.icmph.type     = type;
      icmp_param.data.icmph.code     = code;
      icmp_param.data.icmph.un.gateway = info;
      icmp_param.data.icmph.checksum       = 0;
      icmp_param.skb      = skb_in;
      icmp_param.offset = skb_network_offset(skb_in);
      inet_sk(icmp_socket->sk)->tos = tos;
      ipc.addr = iph->saddr;
      ipc.opt = &icmp_param.replyopts;

      {
            struct flowi fl = {
                  .nl_u = {
                        .ip4_u = {
                              .daddr = icmp_param.replyopts.srr ?
                                    icmp_param.replyopts.faddr :
                                    iph->saddr,
                              .saddr = saddr,
                              .tos = RT_TOS(tos)
                        }
                  },
                  .proto = IPPROTO_ICMP,
                  .uli_u = {
                        .icmpt = {
                              .type = type,
                              .code = code
                        }
                  }
            };
            security_skb_classify_flow(skb_in, &fl);
            if (ip_route_output_key(&rt, &fl))
                  goto out_unlock;
      }

      if (!icmpv4_xrlim_allow(rt, type, code))
            goto ende;

      /* RFC says return as much as we can without exceeding 576 bytes. */

      room = dst_mtu(&rt->u.dst);
      if (room > 576)
            room = 576;
      room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen;
      room -= sizeof(struct icmphdr);

      icmp_param.data_len = skb_in->len - icmp_param.offset;
      if (icmp_param.data_len > room)
            icmp_param.data_len = room;
      icmp_param.head_len = sizeof(struct icmphdr);

      icmp_push_reply(&icmp_param, &ipc, rt);
ende:
      ip_rt_put(rt);
out_unlock:
      icmp_xmit_unlock();
out:;
}


/*
 *    Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH.
 */

static void icmp_unreach(struct sk_buff *skb)
{
      struct iphdr *iph;
      struct icmphdr *icmph;
      int hash, protocol;
      struct net_protocol *ipprot;
      struct sock *raw_sk;
      u32 info = 0;

      /*
       *    Incomplete header ?
       *    Only checks for the IP header, there should be an
       *    additional check for longer headers in upper levels.
       */

      if (!pskb_may_pull(skb, sizeof(struct iphdr)))
            goto out_err;

      icmph = icmp_hdr(skb);
      iph   = (struct iphdr *)skb->data;

      if (iph->ihl < 5) /* Mangled header, drop. */
            goto out_err;

      if (icmph->type == ICMP_DEST_UNREACH) {
            switch (icmph->code & 15) {
            case ICMP_NET_UNREACH:
            case ICMP_HOST_UNREACH:
            case ICMP_PROT_UNREACH:
            case ICMP_PORT_UNREACH:
                  break;
            case ICMP_FRAG_NEEDED:
                  if (ipv4_config.no_pmtu_disc) {
                        LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: "
                                           "fragmentation needed "
                                           "and DF set.\n",
                                     NIPQUAD(iph->daddr));
                  } else {
                        info = ip_rt_frag_needed(iph,
                                         ntohs(icmph->un.frag.mtu));
                        if (!info)
                              goto out;
                  }
                  break;
            case ICMP_SR_FAILED:
                  LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: Source "
                                     "Route Failed.\n",
                               NIPQUAD(iph->daddr));
                  break;
            default:
                  break;
            }
            if (icmph->code > NR_ICMP_UNREACH)
                  goto out;
      } else if (icmph->type == ICMP_PARAMETERPROB)
            info = ntohl(icmph->un.gateway) >> 24;

      /*
       *    Throw it at our lower layers
       *
       *    RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
       *            header.
       *    RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
       *            transport layer.
       *    RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
       *            transport layer.
       */

      /*
       *    Check the other end isnt violating RFC 1122. Some routers send
       *    bogus responses to broadcast frames. If you see this message
       *    first check your netmask matches at both ends, if it does then
       *    get the other vendor to fix their kit.
       */

      if (!sysctl_icmp_ignore_bogus_error_responses &&
          inet_addr_type(iph->daddr) == RTN_BROADCAST) {
            if (net_ratelimit())
                  printk(KERN_WARNING "%u.%u.%u.%u sent an invalid ICMP "
                                  "type %u, code %u "
                                  "error to a broadcast: %u.%u.%u.%u on %s\n",
                         NIPQUAD(ip_hdr(skb)->saddr),
                         icmph->type, icmph->code,
                         NIPQUAD(iph->daddr),
                         skb->dev->name);
            goto out;
      }

      /* Checkin full IP header plus 8 bytes of protocol to
       * avoid additional coding at protocol handlers.
       */
      if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
            goto out;

      iph = (struct iphdr *)skb->data;
      protocol = iph->protocol;

      /*
       *    Deliver ICMP message to raw sockets. Pretty useless feature?
       */

      /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */
      hash = protocol & (MAX_INET_PROTOS - 1);
      read_lock(&raw_v4_lock);
      if ((raw_sk = sk_head(&raw_v4_htable[hash])) != NULL) {
            while ((raw_sk = __raw_v4_lookup(raw_sk, protocol, iph->daddr,
                                     iph->saddr,
                                     skb->dev->ifindex)) != NULL) {
                  raw_err(raw_sk, skb, info);
                  raw_sk = sk_next(raw_sk);
                  iph = (struct iphdr *)skb->data;
            }
      }
      read_unlock(&raw_v4_lock);

      rcu_read_lock();
      ipprot = rcu_dereference(inet_protos[hash]);
      if (ipprot && ipprot->err_handler)
            ipprot->err_handler(skb, info);
      rcu_read_unlock();

out:
      return;
out_err:
      ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
      goto out;
}


/*
 *    Handle ICMP_REDIRECT.
 */

static void icmp_redirect(struct sk_buff *skb)
{
      struct iphdr *iph;

      if (skb->len < sizeof(struct iphdr))
            goto out_err;

      /*
       *    Get the copied header of the packet that caused the redirect
       */
      if (!pskb_may_pull(skb, sizeof(struct iphdr)))
            goto out;

      iph = (struct iphdr *)skb->data;

      switch (icmp_hdr(skb)->code & 7) {
      case ICMP_REDIR_NET:
      case ICMP_REDIR_NETTOS:
            /*
             * As per RFC recommendations now handle it as a host redirect.
             */
      case ICMP_REDIR_HOST:
      case ICMP_REDIR_HOSTTOS:
            ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr,
                         icmp_hdr(skb)->un.gateway,
                         iph->saddr, skb->dev);
            break;
      }
out:
      return;
out_err:
      ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
      goto out;
}

/*
 *    Handle ICMP_ECHO ("ping") requests.
 *
 *    RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
 *            requests.
 *    RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
 *            included in the reply.
 *    RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
 *            echo requests, MUST have default=NOT.
 *    See also WRT handling of options once they are done and working.
 */

static void icmp_echo(struct sk_buff *skb)
{
      if (!sysctl_icmp_echo_ignore_all) {
            struct icmp_bxm icmp_param;

            icmp_param.data.icmph      = *icmp_hdr(skb);
            icmp_param.data.icmph.type = ICMP_ECHOREPLY;
            icmp_param.skb             = skb;
            icmp_param.offset    = 0;
            icmp_param.data_len        = skb->len;
            icmp_param.head_len        = sizeof(struct icmphdr);
            icmp_reply(&icmp_param, skb);
      }
}

/*
 *    Handle ICMP Timestamp requests.
 *    RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
 *            SHOULD be in the kernel for minimum random latency.
 *            MUST be accurate to a few minutes.
 *            MUST be updated at least at 15Hz.
 */
static void icmp_timestamp(struct sk_buff *skb)
{
      struct timeval tv;
      struct icmp_bxm icmp_param;
      /*
       *    Too short.
       */
      if (skb->len < 4)
            goto out_err;

      /*
       *    Fill in the current time as ms since midnight UT:
       */
      do_gettimeofday(&tv);
      icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * 1000 +
                               tv.tv_usec / 1000);
      icmp_param.data.times[2] = icmp_param.data.times[1];
      if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4))
            BUG();
      icmp_param.data.icmph      = *icmp_hdr(skb);
      icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
      icmp_param.data.icmph.code = 0;
      icmp_param.skb             = skb;
      icmp_param.offset    = 0;
      icmp_param.data_len        = 0;
      icmp_param.head_len        = sizeof(struct icmphdr) + 12;
      icmp_reply(&icmp_param, skb);
out:
      return;
out_err:
      ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
      goto out;
}


/*
 *    Handle ICMP_ADDRESS_MASK requests.  (RFC950)
 *
 * RFC1122 (3.2.2.9).  A host MUST only send replies to
 * ADDRESS_MASK requests if it's been configured as an address mask
 * agent.  Receiving a request doesn't constitute implicit permission to
 * act as one. Of course, implementing this correctly requires (SHOULD)
 * a way to turn the functionality on and off.  Another one for sysctl(),
 * I guess. -- MS
 *
 * RFC1812 (4.3.3.9).   A router MUST implement it.
 *                A router SHOULD have switch turning it on/off.
 *                      This switch MUST be ON by default.
 *
 * Gratuitous replies, zero-source replies are not implemented,
 * that complies with RFC. DO NOT implement them!!! All the idea
 * of broadcast addrmask replies as specified in RFC950 is broken.
 * The problem is that it is not uncommon to have several prefixes
 * on one physical interface. Moreover, addrmask agent can even be
 * not aware of existing another prefixes.
 * If source is zero, addrmask agent cannot choose correct prefix.
 * Gratuitous mask announcements suffer from the same problem.
 * RFC1812 explains it, but still allows to use ADDRMASK,
 * that is pretty silly. --ANK
 *
 * All these rules are so bizarre, that I removed kernel addrmask
 * support at all. It is wrong, it is obsolete, nobody uses it in
 * any case. --ANK
 *
 * Furthermore you can do it with a usermode address agent program
 * anyway...
 */

static void icmp_address(struct sk_buff *skb)
{
#if 0
      if (net_ratelimit())
            printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n");
#endif
}

/*
 * RFC1812 (4.3.3.9).   A router SHOULD listen all replies, and complain
 *                loudly if an inconsistency is found.
 */

static void icmp_address_reply(struct sk_buff *skb)
{
      struct rtable *rt = (struct rtable *)skb->dst;
      struct net_device *dev = skb->dev;
      struct in_device *in_dev;
      struct in_ifaddr *ifa;

      if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC))
            goto out;

      in_dev = in_dev_get(dev);
      if (!in_dev)
            goto out;
      rcu_read_lock();
      if (in_dev->ifa_list &&
          IN_DEV_LOG_MARTIANS(in_dev) &&
          IN_DEV_FORWARD(in_dev)) {
            __be32 _mask, *mp;

            mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask);
            BUG_ON(mp == NULL);
            for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) {
                  if (*mp == ifa->ifa_mask &&
                      inet_ifa_match(rt->rt_src, ifa))
                        break;
            }
            if (!ifa && net_ratelimit()) {
                  printk(KERN_INFO "Wrong address mask %u.%u.%u.%u from "
                               "%s/%u.%u.%u.%u\n",
                         NIPQUAD(*mp), dev->name, NIPQUAD(rt->rt_src));
            }
      }
      rcu_read_unlock();
      in_dev_put(in_dev);
out:;
}

static void icmp_discard(struct sk_buff *skb)
{
}

/*
 *    Deal with incoming ICMP packets.
 */
int icmp_rcv(struct sk_buff *skb)
{
      struct icmphdr *icmph;
      struct rtable *rt = (struct rtable *)skb->dst;

      ICMP_INC_STATS_BH(ICMP_MIB_INMSGS);

      switch (skb->ip_summed) {
      case CHECKSUM_COMPLETE:
            if (!csum_fold(skb->csum))
                  break;
            /* fall through */
      case CHECKSUM_NONE:
            skb->csum = 0;
            if (__skb_checksum_complete(skb))
                  goto error;
      }

      if (!pskb_pull(skb, sizeof(struct icmphdr)))
            goto error;

      icmph = icmp_hdr(skb);

      ICMPMSGIN_INC_STATS_BH(icmph->type);
      /*
       *    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)
            goto error;


      /*
       *    Parse the ICMP message
       */

      if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
            /*
             *    RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
             *      silently ignored (we let user decide with a sysctl).
             *    RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
             *      discarded if to broadcast/multicast.
             */
            if ((icmph->type == ICMP_ECHO ||
                 icmph->type == ICMP_TIMESTAMP) &&
                sysctl_icmp_echo_ignore_broadcasts) {
                  goto error;
            }
            if (icmph->type != ICMP_ECHO &&
                icmph->type != ICMP_TIMESTAMP &&
                icmph->type != ICMP_ADDRESS &&
                icmph->type != ICMP_ADDRESSREPLY) {
                  goto error;
            }
      }

      icmp_pointers[icmph->type].handler(skb);

drop:
      kfree_skb(skb);
      return 0;
error:
      ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
      goto drop;
}

/*
 *    This table is the definition of how we handle ICMP.
 */
static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
      [ICMP_ECHOREPLY] = {
            .handler = icmp_discard,
      },
      [1] = {
            .handler = icmp_discard,
            .error = 1,
      },
      [2] = {
            .handler = icmp_discard,
            .error = 1,
      },
      [ICMP_DEST_UNREACH] = {
            .handler = icmp_unreach,
            .error = 1,
      },
      [ICMP_SOURCE_QUENCH] = {
            .handler = icmp_unreach,
            .error = 1,
      },
      [ICMP_REDIRECT] = {
            .handler = icmp_redirect,
            .error = 1,
      },
      [6] = {
            .handler = icmp_discard,
            .error = 1,
      },
      [7] = {
            .handler = icmp_discard,
            .error = 1,
      },
      [ICMP_ECHO] = {
            .handler = icmp_echo,
      },
      [9] = {
            .handler = icmp_discard,
            .error = 1,
      },
      [10] = {
            .handler = icmp_discard,
            .error = 1,
      },
      [ICMP_TIME_EXCEEDED] = {
            .handler = icmp_unreach,
            .error = 1,
      },
      [ICMP_PARAMETERPROB] = {
            .handler = icmp_unreach,
            .error = 1,
      },
      [ICMP_TIMESTAMP] = {
            .handler = icmp_timestamp,
      },
      [ICMP_TIMESTAMPREPLY] = {
            .handler = icmp_discard,
      },
      [ICMP_INFO_REQUEST] = {
            .handler = icmp_discard,
      },
      [ICMP_INFO_REPLY] = {
            .handler = icmp_discard,
      },
      [ICMP_ADDRESS] = {
            .handler = icmp_address,
      },
      [ICMP_ADDRESSREPLY] = {
            .handler = icmp_address_reply,
      },
};

void __init icmp_init(struct net_proto_family *ops)
{
      struct inet_sock *inet;
      int i;

      for_each_possible_cpu(i) {
            int err;

            err = sock_create_kern(PF_INET, SOCK_RAW, IPPROTO_ICMP,
                               &per_cpu(__icmp_socket, i));

            if (err < 0)
                  panic("Failed to create the ICMP control socket.\n");

            per_cpu(__icmp_socket, i)->sk->sk_allocation = GFP_ATOMIC;

            /* Enough space for 2 64K ICMP packets, including
             * sk_buff struct overhead.
             */
            per_cpu(__icmp_socket, i)->sk->sk_sndbuf =
                  (2 * ((64 * 1024) + sizeof(struct sk_buff)));

            inet = inet_sk(per_cpu(__icmp_socket, i)->sk);
            inet->uc_ttl = -1;
            inet->pmtudisc = IP_PMTUDISC_DONT;

            /* Unhash it so that IP input processing does not even
             * see it, we do not wish this socket to see incoming
             * packets.
             */
            per_cpu(__icmp_socket, i)->sk->sk_prot->unhash(per_cpu(__icmp_socket, i)->sk);
      }
}

EXPORT_SYMBOL(icmp_err_convert);
EXPORT_SYMBOL(icmp_send);
EXPORT_SYMBOL(icmp_statistics);
EXPORT_SYMBOL(xrlim_allow);

Generated by  Doxygen 1.6.0   Back to index