// SPDX-License-Identifier: GPL-2.0-or-later /* * NET3: Implementation of the ICMP protocol layer. * * Alan Cox, * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * 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 - prandom_u32_max(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 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 (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); }