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icmp.c
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/*
* 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/config.h>
#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/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;
__u32 times[3];
} data;
int head_len;
struct ip_options replyopts;
unsigned char optbuf[40];
};
/*
* Statistics
*/
DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics);
/* 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;
int sysctl_icmp_echo_ignore_broadcasts;
/* Control parameter - ignore bogus broadcast responses? */
int sysctl_icmp_ignore_bogus_error_responses;
/*
* 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 = 1 * HZ;
int sysctl_icmp_ratemask = 0x1818;
int sysctl_icmp_errors_use_inbound_ifaddr;
/*
* ICMP control array. This specifies what to do with each ICMP.
*/
struct icmp_control {
int output_entry; /* Field for increment on output */
int input_entry; /* Field for increment on input */
void (*handler)(struct sk_buff *skb);
short error; /* This ICMP is classed as an error message */
};
static 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
*/
static void icmp_out_count(int type)
{
if (type <= NR_ICMP_TYPES) {
ICMP_INC_STATS(icmp_pointers[type].output_entry);
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;
unsigned int 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;
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);
if ((skb = skb_peek(&icmp_socket->sk->sk_write_queue)) != NULL) {
struct icmphdr *icmph = skb->h.icmph;
unsigned int 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;
u32 daddr;
if (ip_options_echo(&icmp_param->replyopts, skb))
goto out;
if (icmp_xmit_lock())
return;
icmp_param->data.icmph.checksum = 0;
icmp_out_count(icmp_param->data.icmph.type);
inet->tos = skb->nh.iph->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(skb->nh.iph->tos) } },
.proto = IPPROTO_ICMP };
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();
out:;
}
/*
* 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, u32 info)
{
struct iphdr *iph;
int room;
struct icmp_bxm icmp_param;
struct rtable *rt = (struct rtable *)skb_in->dst;
struct ipcm_cookie ipc;
u32 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 = skb_in->nh.iph;
if ((u8 *)iph < skb_in->head || (u8 *)(iph + 1) > 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_in->nh.raw +
(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)) {
if (sysctl_icmp_errors_use_inbound_ifaddr)
saddr = inet_select_addr(skb_in->dev, 0, RT_SCOPE_LINK);
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 ende;
/*
* 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_in->nh.raw - skb_in->data;
icmp_out_count(icmp_param.data.icmph.type);
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
}
}
};
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 = skb->h.icmph;
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(
printk(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(
printk(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(skb->nh.iph->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;
unsigned long ip;
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;
ip = iph->daddr;
switch (skb->h.icmph->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(skb->nh.iph->saddr, ip, skb->h.icmph->un.gateway,
iph->saddr, iph->tos, 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 = *skb->h.icmph;
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 = *skb->h.icmph;
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)) {
u32 _mask, *mp;
mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask);
if (mp == NULL)
BUG();
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_HW:
if (!(u16)csum_fold(skb->csum))
break;
NETDEBUG(if (net_ratelimit())
printk(KERN_DEBUG "icmp v4 hw csum failure\n"));
case CHECKSUM_NONE:
if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0)))
goto error;
default:;
}
if (!pskb_pull(skb, sizeof(struct icmphdr)))
goto error;
icmph = skb->h.icmph;
/*
* 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 &&
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_INC_STATS_BH(icmp_pointers[icmph->type].input_entry);
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 struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
[ICMP_ECHOREPLY] = {