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WSL2-Linux-Kernel/net/ipv4/icmp.c

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C
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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* NET3: Implementation of the ICMP protocol layer.
*
* Alan Cox, <alan@lxorguk.ukuu.org.uk>
*
* 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
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#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 <linux/slab.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 <net/ping.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <net/checksum.h>
#include <net/xfrm.h>
#include <net/inet_common.h>
#include <net/ip_fib.h>
#include <net/l3mdev.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_data replyopts;
};
/* 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'. */
const 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,
},
};
EXPORT_SYMBOL(icmp_err_convert);
/*
* ICMP control array. This specifies what to do with each ICMP.
*/
struct icmp_control {
enum skb_drop_reason (*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];
static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);
/* Called with BH disabled */
static inline struct sock *icmp_xmit_lock(struct net *net)
{
struct sock *sk;
sk = this_cpu_read(ipv4_icmp_sk);
if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
/* This can happen if the output path signals a
* dst_link_failure() for an outgoing ICMP packet.
*/
return NULL;
}
sock_net_set(sk, net);
return sk;
}
static inline void icmp_xmit_unlock(struct sock *sk)
{
sock_net_set(sk, &init_net);
spin_unlock(&sk->sk_lock.slock);
}
int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
int sysctl_icmp_msgs_burst __read_mostly = 50;
static struct {
spinlock_t lock;
u32 credit;
u32 stamp;
} icmp_global = {
.lock = __SPIN_LOCK_UNLOCKED(icmp_global.lock),
};
/**
* icmp_global_allow - Are we allowed to send one more ICMP message ?
*
* Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
* Returns false if we reached the limit and can not send another packet.
* Note: called with BH disabled
*/
bool icmp_global_allow(void)
{
u32 credit, delta, incr = 0, now = (u32)jiffies;
bool rc = false;
/* Check if token bucket is empty and cannot be refilled
* without taking the spinlock. The READ_ONCE() are paired
* with the following WRITE_ONCE() in this same function.
*/
if (!READ_ONCE(icmp_global.credit)) {
delta = min_t(u32, now - READ_ONCE(icmp_global.stamp), HZ);
if (delta < HZ / 50)
return false;
}
spin_lock(&icmp_global.lock);
delta = min_t(u32, now - icmp_global.stamp, HZ);
if (delta >= HZ / 50) {
incr = READ_ONCE(sysctl_icmp_msgs_per_sec) * delta / HZ;
if (incr)
WRITE_ONCE(icmp_global.stamp, now);
}
credit = min_t(u32, icmp_global.credit + incr,
READ_ONCE(sysctl_icmp_msgs_burst));
if (credit) {
/* We want to use a credit of one in average, but need to randomize
* it for security reasons.
*/
credit = max_t(int, credit - get_random_u32_below(3), 0);
rc = true;
}
WRITE_ONCE(icmp_global.credit, credit);
spin_unlock(&icmp_global.lock);
return rc;
}
EXPORT_SYMBOL(icmp_global_allow);
static bool icmpv4_mask_allow(struct net *net, int type, int code)
{
if (type > NR_ICMP_TYPES)
return true;
/* Don't limit PMTU discovery. */
if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
return true;
/* Limit if icmp type is enabled in ratemask. */
if (!((1 << type) & READ_ONCE(net->ipv4.sysctl_icmp_ratemask)))
return true;
return false;
}
static bool icmpv4_global_allow(struct net *net, int type, int code)
{
if (icmpv4_mask_allow(net, type, code))
return true;
if (icmp_global_allow())
return true;
return false;
}
/*
* Send an ICMP frame.
*/
static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
struct flowi4 *fl4, int type, int code)
{
struct dst_entry *dst = &rt->dst;
struct inet_peer *peer;
bool rc = true;
int vif;
if (icmpv4_mask_allow(net, type, code))
goto out;
/* No rate limit on loopback */
if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
goto out;
vif = l3mdev_master_ifindex(dst->dev);
peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1);
rc = inet_peer_xrlim_allow(peer,
READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
if (peer)
inet_putpeer(peer);
out:
return rc;
}
/*
* Maintain the counters used in the SNMP statistics for outgoing ICMP
*/
void icmp_out_count(struct net *net, unsigned char type)
{
ICMPMSGOUT_INC_STATS(net, type);
ICMP_INC_STATS(net, 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 = from;
__wsum csum;
csum = skb_copy_and_csum_bits(icmp_param->skb,
icmp_param->offset + offset,
to, len);
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 sock *sk,
struct icmp_bxm *icmp_param,
struct flowi4 *fl4,
struct ipcm_cookie *ipc, struct rtable **rt)
{
struct sk_buff *skb;
if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
icmp_param->data_len+icmp_param->head_len,
icmp_param->head_len,
ipc, rt, MSG_DONTWAIT) < 0) {
__ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
ip_flush_pending_frames(sk);
} else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
struct icmphdr *icmph = icmp_hdr(skb);
__wsum csum;
struct sk_buff *skb1;
csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
(char *)icmph,
icmp_param->head_len);
skb_queue_walk(&sk->sk_write_queue, skb1) {
csum = csum_add(csum, skb1->csum);
}
icmph->checksum = csum_fold(csum);
skb->ip_summed = CHECKSUM_NONE;
ip_push_pending_frames(sk, fl4);
}
}
/*
* Driving logic for building and sending ICMP messages.
*/
static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
{
struct ipcm_cookie ipc;
struct rtable *rt = skb_rtable(skb);
struct net *net = dev_net(rt->dst.dev);
struct flowi4 fl4;
struct sock *sk;
struct inet_sock *inet;
__be32 daddr, saddr;
u32 mark = IP4_REPLY_MARK(net, skb->mark);
int type = icmp_param->data.icmph.type;
int code = icmp_param->data.icmph.code;
if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb))
return;
/* Needed by both icmp_global_allow and icmp_xmit_lock */
local_bh_disable();
/* global icmp_msgs_per_sec */
if (!icmpv4_global_allow(net, type, code))
goto out_bh_enable;
sk = icmp_xmit_lock(net);
if (!sk)
goto out_bh_enable;
inet = inet_sk(sk);
icmp_param->data.icmph.checksum = 0;
ipcm_init(&ipc);
inet->tos = ip_hdr(skb)->tos;
ipc.sockc.mark = mark;
daddr = ipc.addr = ip_hdr(skb)->saddr;
saddr = fib_compute_spec_dst(skb);
if (icmp_param->replyopts.opt.opt.optlen) {
ipc.opt = &icmp_param->replyopts.opt;
if (ipc.opt->opt.srr)
daddr = icmp_param->replyopts.opt.opt.faddr;
}
memset(&fl4, 0, sizeof(fl4));
fl4.daddr = daddr;
fl4.saddr = saddr;
fl4.flowi4_mark = mark;
fl4.flowi4_uid = sock_net_uid(net, NULL);
fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
fl4.flowi4_proto = IPPROTO_ICMP;
fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt))
goto out_unlock;
if (icmpv4_xrlim_allow(net, rt, &fl4, type, code))
icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
ip_rt_put(rt);
out_unlock:
icmp_xmit_unlock(sk);
out_bh_enable:
local_bh_enable();
}
/*
* The device used for looking up which routing table to use for sending an ICMP
* error is preferably the source whenever it is set, which should ensure the
* icmp error can be sent to the source host, else lookup using the routing
* table of the destination device, else use the main routing table (index 0).
*/
static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
{
struct net_device *route_lookup_dev = NULL;
if (skb->dev)
route_lookup_dev = skb->dev;
else if (skb_dst(skb))
route_lookup_dev = skb_dst(skb)->dev;
return route_lookup_dev;
}
static struct rtable *icmp_route_lookup(struct net *net,
struct flowi4 *fl4,
struct sk_buff *skb_in,
const struct iphdr *iph,
__be32 saddr, u8 tos, u32 mark,
int type, int code,
struct icmp_bxm *param)
{
struct net_device *route_lookup_dev;
struct rtable *rt, *rt2;
struct flowi4 fl4_dec;
int err;
memset(fl4, 0, sizeof(*fl4));
fl4->daddr = (param->replyopts.opt.opt.srr ?
param->replyopts.opt.opt.faddr : iph->saddr);
fl4->saddr = saddr;
fl4->flowi4_mark = mark;
fl4->flowi4_uid = sock_net_uid(net, NULL);
fl4->flowi4_tos = RT_TOS(tos);
fl4->flowi4_proto = IPPROTO_ICMP;
fl4->fl4_icmp_type = type;
fl4->fl4_icmp_code = code;
route_lookup_dev = icmp_get_route_lookup_dev(skb_in);
fl4->flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);
security_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));
rt = ip_route_output_key_hash(net, fl4, skb_in);
if (IS_ERR(rt))
return rt;
/* No need to clone since we're just using its address. */
rt2 = rt;
rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
flowi4_to_flowi(fl4), NULL, 0);
if (!IS_ERR(rt)) {
if (rt != rt2)
return rt;
} else if (PTR_ERR(rt) == -EPERM) {
rt = NULL;
} else
return rt;
err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
if (err)
goto relookup_failed;
if (inet_addr_type_dev_table(net, route_lookup_dev,
fl4_dec.saddr) == RTN_LOCAL) {
rt2 = __ip_route_output_key(net, &fl4_dec);
if (IS_ERR(rt2))
err = PTR_ERR(rt2);
} else {
struct flowi4 fl4_2 = {};
unsigned long orefdst;
fl4_2.daddr = fl4_dec.saddr;
rt2 = ip_route_output_key(net, &fl4_2);
if (IS_ERR(rt2)) {
err = PTR_ERR(rt2);
goto relookup_failed;
}
/* Ugh! */
orefdst = skb_in->_skb_refdst; /* save old refdst */
skb_dst_set(skb_in, NULL);
err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
RT_TOS(tos), rt2->dst.dev);
dst_release(&rt2->dst);
rt2 = skb_rtable(skb_in);
skb_in->_skb_refdst = orefdst; /* restore old refdst */
}
if (err)
goto relookup_failed;
rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
flowi4_to_flowi(&fl4_dec), NULL,
XFRM_LOOKUP_ICMP);
if (!IS_ERR(rt2)) {
dst_release(&rt->dst);
memcpy(fl4, &fl4_dec, sizeof(*fl4));
rt = rt2;
} else if (PTR_ERR(rt2) == -EPERM) {
if (rt)
dst_release(&rt->dst);
return rt2;
} else {
err = PTR_ERR(rt2);
goto relookup_failed;
}
return rt;
relookup_failed:
if (rt)
return rt;
return ERR_PTR(err);
}
/*
* 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,
const struct ip_options *opt)
{
struct iphdr *iph;
int room;
struct icmp_bxm icmp_param;
struct rtable *rt = skb_rtable(skb_in);
struct ipcm_cookie ipc;
struct flowi4 fl4;
__be32 saddr;
u8 tos;
u32 mark;
struct net *net;
struct sock *sk;
if (!rt)
goto out;
if (rt->dst.dev)
net = dev_net(rt->dst.dev);
else if (skb_in->dev)
net = dev_net(skb_in->dev);
else
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_network_header(skb_in) + sizeof(*iph)) >
skb_tail_pointer(skb_in))
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)
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;
}
}
/* Needed by both icmp_global_allow and icmp_xmit_lock */
local_bh_disable();
/* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
* incoming dev is loopback. If outgoing dev change to not be
* loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
*/
if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
!icmpv4_global_allow(net, type, code))
goto out_bh_enable;
sk = icmp_xmit_lock(net);
if (!sk)
goto out_bh_enable;
/*
* Construct source address and options.
*/
saddr = iph->daddr;
if (!(rt->rt_flags & RTCF_LOCAL)) {
struct net_device *dev = NULL;
rcu_read_lock();
if (rt_is_input_route(rt) &&
READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
if (dev)
saddr = inet_select_addr(dev, iph->saddr,
RT_SCOPE_LINK);
else
saddr = 0;
rcu_read_unlock();
}
tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
IPTOS_PREC_INTERNETCONTROL) :
iph->tos;
mark = IP4_REPLY_MARK(net, skb_in->mark);
if (__ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in, opt))
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(sk)->tos = tos;
ipcm_init(&ipc);
ipc.addr = iph->saddr;
ipc.opt = &icmp_param.replyopts.opt;
ipc.sockc.mark = mark;
rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,
type, code, &icmp_param);
if (IS_ERR(rt))
goto out_unlock;
/* peer icmp_ratelimit */
if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
goto ende;
/* RFC says return as much as we can without exceeding 576 bytes. */
room = dst_mtu(&rt->dst);
if (room > 576)
room = 576;
room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.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);
/* if we don't have a source address at this point, fall back to the
* dummy address instead of sending out a packet with a source address
* of 0.0.0.0
*/
if (!fl4.saddr)
fl4.saddr = htonl(INADDR_DUMMY);
icmp_push_reply(sk, &icmp_param, &fl4, &ipc, &rt);
ende:
ip_rt_put(rt);
out_unlock:
icmp_xmit_unlock(sk);
out_bh_enable:
local_bh_enable();
out:;
}
EXPORT_SYMBOL(__icmp_send);
#if IS_ENABLED(CONFIG_NF_NAT)
#include <net/netfilter/nf_conntrack.h>
void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
{
struct sk_buff *cloned_skb = NULL;
struct ip_options opts = { 0 };
enum ip_conntrack_info ctinfo;
struct nf_conn *ct;
__be32 orig_ip;
ct = nf_ct_get(skb_in, &ctinfo);
if (!ct || !(ct->status & IPS_SRC_NAT)) {
__icmp_send(skb_in, type, code, info, &opts);
return;
}
if (skb_shared(skb_in))
skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);
if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
(skb_network_header(skb_in) + sizeof(struct iphdr)) >
skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
skb_network_offset(skb_in) + sizeof(struct iphdr))))
goto out;
orig_ip = ip_hdr(skb_in)->saddr;
ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
__icmp_send(skb_in, type, code, info, &opts);
ip_hdr(skb_in)->saddr = orig_ip;
out:
consume_skb(cloned_skb);
}
EXPORT_SYMBOL(icmp_ndo_send);
#endif
static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
{
const struct iphdr *iph = (const struct iphdr *)skb->data;
const struct net_protocol *ipprot;
int protocol = iph->protocol;
/* 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)) {
__ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
return;
}
raw_icmp_error(skb, protocol, info);
ipprot = rcu_dereference(inet_protos[protocol]);
if (ipprot && ipprot->err_handler)
ipprot->err_handler(skb, info);
}
static bool icmp_tag_validation(int proto)
{
bool ok;
rcu_read_lock();
ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
rcu_read_unlock();
return ok;
}
/*
* Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
* ICMP_PARAMETERPROB.
*/
static enum skb_drop_reason icmp_unreach(struct sk_buff *skb)
{
enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
const struct iphdr *iph;
struct icmphdr *icmph;
struct net *net;
u32 info = 0;
net = dev_net(skb_dst(skb)->dev);
/*
* 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 = (const struct iphdr *)skb->data;
if (iph->ihl < 5) { /* Mangled header, drop. */
reason = SKB_DROP_REASON_IP_INHDR;
goto out_err;
}
switch (icmph->type) {
case 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:
/* for documentation of the ip_no_pmtu_disc
* values please see
* Documentation/networking/ip-sysctl.rst
*/
switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
default:
net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
&iph->daddr);
break;
case 2:
goto out;
case 3:
if (!icmp_tag_validation(iph->protocol))
goto out;
fallthrough;
case 0:
info = ntohs(icmph->un.frag.mtu);
}
break;
case ICMP_SR_FAILED:
net_dbg_ratelimited("%pI4: Source Route Failed\n",
&iph->daddr);
break;
default:
break;
}
if (icmph->code > NR_ICMP_UNREACH)
goto out;
break;
case ICMP_PARAMETERPROB:
info = ntohl(icmph->un.gateway) >> 24;
break;
case ICMP_TIME_EXCEEDED:
__ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
if (icmph->code == ICMP_EXC_FRAGTIME)
goto out;
break;
}
/*
* 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 isn't 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 (!READ_ONCE(net->ipv4.sysctl_icmp_ignore_bogus_error_responses) &&
inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
&ip_hdr(skb)->saddr,
icmph->type, icmph->code,
&iph->daddr, skb->dev->name);
goto out;
}
icmp_socket_deliver(skb, info);
out:
return reason;
out_err:
__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
return reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
}
/*
* Handle ICMP_REDIRECT.
*/
static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
{
if (skb->len < sizeof(struct iphdr)) {
__ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
return SKB_DROP_REASON_PKT_TOO_SMALL;
}
if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
/* there aught to be a stat */
return SKB_DROP_REASON_NOMEM;
}
icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
return SKB_NOT_DROPPED_YET;
}
/*
* Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") 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.
* RFC 8335: 8 MUST have a config option to enable/disable ICMP
* Extended Echo Functionality, MUST be disabled by default
* See also WRT handling of options once they are done and working.
*/
static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
{
struct icmp_bxm icmp_param;
struct net *net;
net = dev_net(skb_dst(skb)->dev);
/* should there be an ICMP stat for ignored echos? */
if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
return SKB_NOT_DROPPED_YET;
icmp_param.data.icmph = *icmp_hdr(skb);
icmp_param.skb = skb;
icmp_param.offset = 0;
icmp_param.data_len = skb->len;
icmp_param.head_len = sizeof(struct icmphdr);
if (icmp_param.data.icmph.type == ICMP_ECHO)
icmp_param.data.icmph.type = ICMP_ECHOREPLY;
else if (!icmp_build_probe(skb, &icmp_param.data.icmph))
return SKB_NOT_DROPPED_YET;
icmp_reply(&icmp_param, skb);
return SKB_NOT_DROPPED_YET;
}
/* Helper for icmp_echo and icmpv6_echo_reply.
* Searches for net_device that matches PROBE interface identifier
* and builds PROBE reply message in icmphdr.
*
* Returns false if PROBE responses are disabled via sysctl
*/
bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
{
struct icmp_ext_hdr *ext_hdr, _ext_hdr;
struct icmp_ext_echo_iio *iio, _iio;
struct net *net = dev_net(skb->dev);
struct net_device *dev;
char buff[IFNAMSIZ];
u16 ident_len;
u8 status;
if (!READ_ONCE(net->ipv4.sysctl_icmp_echo_enable_probe))
return false;
/* We currently only support probing interfaces on the proxy node
* Check to ensure L-bit is set
*/
if (!(ntohs(icmphdr->un.echo.sequence) & 1))
return false;
/* Clear status bits in reply message */
icmphdr->un.echo.sequence &= htons(0xFF00);
if (icmphdr->type == ICMP_EXT_ECHO)
icmphdr->type = ICMP_EXT_ECHOREPLY;
else
icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
/* Size of iio is class_type dependent.
* Only check header here and assign length based on ctype in the switch statement
*/
iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_iio);
if (!ext_hdr || !iio)
goto send_mal_query;
if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
ntohs(iio->extobj_hdr.length) > sizeof(_iio))
goto send_mal_query;
ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
iio = skb_header_pointer(skb, sizeof(_ext_hdr),
sizeof(iio->extobj_hdr) + ident_len, &_iio);
if (!iio)
goto send_mal_query;
status = 0;
dev = NULL;
switch (iio->extobj_hdr.class_type) {
case ICMP_EXT_ECHO_CTYPE_NAME:
if (ident_len >= IFNAMSIZ)
goto send_mal_query;
memset(buff, 0, sizeof(buff));
memcpy(buff, &iio->ident.name, ident_len);
dev = dev_get_by_name(net, buff);
break;
case ICMP_EXT_ECHO_CTYPE_INDEX:
if (ident_len != sizeof(iio->ident.ifindex))
goto send_mal_query;
dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
break;
case ICMP_EXT_ECHO_CTYPE_ADDR:
if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
iio->ident.addr.ctype3_hdr.addrlen)
goto send_mal_query;
switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
case ICMP_AFI_IP:
if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
goto send_mal_query;
dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr);
break;
#if IS_ENABLED(CONFIG_IPV6)
case ICMP_AFI_IP6:
if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
goto send_mal_query;
dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
dev_hold(dev);
break;
#endif
default:
goto send_mal_query;
}
break;
default:
goto send_mal_query;
}
if (!dev) {
icmphdr->code = ICMP_EXT_CODE_NO_IF;
return true;
}
/* Fill bits in reply message */
if (dev->flags & IFF_UP)
status |= ICMP_EXT_ECHOREPLY_ACTIVE;
if (__in_dev_get_rcu(dev) && __in_dev_get_rcu(dev)->ifa_list)
status |= ICMP_EXT_ECHOREPLY_IPV4;
if (!list_empty(&rcu_dereference(dev->ip6_ptr)->addr_list))
status |= ICMP_EXT_ECHOREPLY_IPV6;
dev_put(dev);
icmphdr->un.echo.sequence |= htons(status);
return true;
send_mal_query:
icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
return true;
}
EXPORT_SYMBOL_GPL(icmp_build_probe);
/*
* 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 enum skb_drop_reason icmp_timestamp(struct sk_buff *skb)
{
struct icmp_bxm icmp_param;
/*
* Too short.
*/
if (skb->len < 4)
goto out_err;
/*
* Fill in the current time as ms since midnight UT:
*/
icmp_param.data.times[1] = inet_current_timestamp();
icmp_param.data.times[2] = icmp_param.data.times[1];
BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4));
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);
return SKB_NOT_DROPPED_YET;
out_err:
__ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
return SKB_DROP_REASON_PKT_TOO_SMALL;
}
static enum skb_drop_reason icmp_discard(struct sk_buff *skb)
{
/* pretend it was a success */
return SKB_NOT_DROPPED_YET;
}
/*
* Deal with incoming ICMP packets.
*/
int icmp_rcv(struct sk_buff *skb)
{
enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
struct rtable *rt = skb_rtable(skb);
struct net *net = dev_net(rt->dst.dev);
struct icmphdr *icmph;
if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
struct sec_path *sp = skb_sec_path(skb);
int nh;
if (!(sp && sp->xvec[sp->len - 1]->props.flags &
XFRM_STATE_ICMP)) {
reason = SKB_DROP_REASON_XFRM_POLICY;
goto drop;
}
if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
goto drop;
nh = skb_network_offset(skb);
skb_set_network_header(skb, sizeof(*icmph));
if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN,
skb)) {
reason = SKB_DROP_REASON_XFRM_POLICY;
goto drop;
}
skb_set_network_header(skb, nh);
}
__ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
if (skb_checksum_simple_validate(skb))
goto csum_error;
if (!pskb_pull(skb, sizeof(*icmph)))
goto error;
icmph = icmp_hdr(skb);
ICMPMSGIN_INC_STATS(net, icmph->type);
/* Check for ICMP Extended Echo (PROBE) messages */
if (icmph->type == ICMP_EXT_ECHO) {
/* We can't use icmp_pointers[].handler() because it is an array of
* size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
*/
reason = icmp_echo(skb);
goto reason_check;
}
if (icmph->type == ICMP_EXT_ECHOREPLY) {
reason = ping_rcv(skb);
goto reason_check;
}
/*
* 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) {
reason = SKB_DROP_REASON_UNHANDLED_PROTO;
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) &&
READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
reason = SKB_DROP_REASON_INVALID_PROTO;
goto error;
}
if (icmph->type != ICMP_ECHO &&
icmph->type != ICMP_TIMESTAMP &&
icmph->type != ICMP_ADDRESS &&
icmph->type != ICMP_ADDRESSREPLY) {
reason = SKB_DROP_REASON_INVALID_PROTO;
goto error;
}
}
reason = icmp_pointers[icmph->type].handler(skb);
reason_check:
if (!reason) {
consume_skb(skb);
return NET_RX_SUCCESS;
}
drop:
kfree_skb_reason(skb, reason);
return NET_RX_DROP;
csum_error:
reason = SKB_DROP_REASON_ICMP_CSUM;
__ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
error:
__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
goto drop;
}
static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
{
struct icmp_extobj_hdr *objh, _objh;
struct icmp_ext_hdr *exth, _exth;
u16 olen;
exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
if (!exth)
return false;
if (exth->version != 2)
return true;
if (exth->checksum &&
csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
return false;
off += sizeof(_exth);
while (off < skb->len) {
objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
if (!objh)
return false;
olen = ntohs(objh->length);
if (olen < sizeof(_objh))
return false;
off += olen;
if (off > skb->len)
return false;
}
return true;
}
void ip_icmp_error_rfc4884(const struct sk_buff *skb,
struct sock_ee_data_rfc4884 *out,
int thlen, int off)
{
int hlen;
/* original datagram headers: end of icmph to payload (skb->data) */
hlen = -skb_transport_offset(skb) - thlen;
/* per rfc 4884: minimal datagram length of 128 bytes */
if (off < 128 || off < hlen)
return;
/* kernel has stripped headers: return payload offset in bytes */
off -= hlen;
if (off + sizeof(struct icmp_ext_hdr) > skb->len)
return;
out->len = off;
if (!ip_icmp_error_rfc4884_validate(skb, off))
out->flags |= SO_EE_RFC4884_FLAG_INVALID;
}
EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
int icmp_err(struct sk_buff *skb, u32 info)
{
struct iphdr *iph = (struct iphdr *)skb->data;
int offset = iph->ihl<<2;
struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
int type = icmp_hdr(skb)->type;
int code = icmp_hdr(skb)->code;
struct net *net = dev_net(skb->dev);
/*
* Use ping_err to handle all icmp errors except those
* triggered by ICMP_ECHOREPLY which sent from kernel.
*/
if (icmph->type != ICMP_ECHOREPLY) {
ping_err(skb, offset, info);
return 0;
}
if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
else if (type == ICMP_REDIRECT)
ipv4_redirect(skb, net, 0, IPPROTO_ICMP);
return 0;
}
/*
* This table is the definition of how we handle ICMP.
*/
static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
[ICMP_ECHOREPLY] = {
.handler = ping_rcv,
},
[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_discard,
},
[ICMP_ADDRESSREPLY] = {
.handler = icmp_discard,
},
};
static int __net_init icmp_sk_init(struct net *net)
{
/* Control parameters for ECHO replies. */
net->ipv4.sysctl_icmp_echo_ignore_all = 0;
net->ipv4.sysctl_icmp_echo_enable_probe = 0;
net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
/* Control parameter - ignore bogus broadcast responses? */
net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 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)
*/
net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
net->ipv4.sysctl_icmp_ratemask = 0x1818;
net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
return 0;
}
static struct pernet_operations __net_initdata icmp_sk_ops = {
.init = icmp_sk_init,
};
int __init icmp_init(void)
{
int err, i;
for_each_possible_cpu(i) {
struct sock *sk;
err = inet_ctl_sock_create(&sk, PF_INET,
SOCK_RAW, IPPROTO_ICMP, &init_net);
if (err < 0)
return err;
per_cpu(ipv4_icmp_sk, i) = sk;
/* Enough space for 2 64K ICMP packets, including
* sk_buff/skb_shared_info struct overhead.
*/
sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
/*
* Speedup sock_wfree()
*/
sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
}
return register_pernet_subsys(&icmp_sk_ops);
}
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