/* * NET3: Implementation of the ICMP protocol layer. * * Alan Cox, * * Version: $Id: icmp.c,v 1.52.2.4 1999/11/16 02:28:40 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: * 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 * * RFC1122 (Host Requirements -- Comm. Layer) Status: * (boy, are there a lot of rules for ICMP) * 3.2.2 (Generic ICMP stuff) * MUST discard messages of unknown type. (OK) * MUST copy at least the first 8 bytes from the offending packet * when sending ICMP errors. (OBSOLETE -- see RFC1812) * MUST pass received ICMP errors up to protocol level. (OK) * SHOULD send ICMP errors with TOS == 0. (OBSOLETE -- see RFC1812) * MUST NOT send ICMP errors in reply to: * ICMP errors (OK) * Broadcast/multicast datagrams (OK) * MAC broadcasts (OK) * Non-initial fragments (OK) * Datagram with a source address that isn't a single host. (OK) * 3.2.2.1 (Destination Unreachable) * All the rules govern the IP layer, and are dealt with in ip.c, not here. * 3.2.2.2 (Redirect) * Host SHOULD NOT send ICMP_REDIRECTs. (OK) * MUST update routing table in response to host or network redirects. * (host OK, network OBSOLETE) * SHOULD drop redirects if they're not from directly connected gateway * (OK -- we drop it if it's not from our old gateway, which is close * enough) * 3.2.2.3 (Source Quench) * MUST pass incoming SOURCE_QUENCHs to transport layer (OK) * Other requirements are dealt with at the transport layer. * 3.2.2.4 (Time Exceeded) * MUST pass TIME_EXCEEDED to transport layer (OK) * Other requirements dealt with at IP (generating TIME_EXCEEDED). * 3.2.2.5 (Parameter Problem) * SHOULD generate these (OK) * MUST pass received PARAMPROBLEM to transport layer (NOT YET) * [Solaris 2.X seems to assert EPROTO when this occurs] -- AC * 3.2.2.6 (Echo Request/Reply) * MUST reply to ECHO_REQUEST, and give app to do ECHO stuff (OK, OK) * MAY discard broadcast ECHO_REQUESTs. (Configurable with a sysctl.) * MUST reply using same source address as the request was sent to. * We're OK for unicast ECHOs, and it doesn't say anything about * how to handle broadcast ones, since it's optional. * MUST copy data from REQUEST to REPLY (OK) * unless it would require illegal fragmentation (OK) * MUST pass REPLYs to transport/user layer (OK) * MUST use any provided source route (reversed) for REPLY. (NOT YET) * 3.2.2.7 (Information Request/Reply) * MUST NOT implement this. (I guess that means silently discard...?) (OK) * 3.2.2.8 (Timestamp Request/Reply) * MAY implement (OK) * SHOULD be in-kernel for "minimum variability" (OK) * MAY discard broadcast REQUESTs. (OK, but see source for inconsistency) * MUST reply using same source address as the request was sent to. (OK) * MUST reverse source route, as per ECHO (NOT YET) * MUST pass REPLYs to transport/user layer (requires RAW, just like * ECHO) (OK) * MUST update clock for timestamp at least 15 times/sec (OK) * MUST be "correct within a few minutes" (OK) * 3.2.2.9 (Address Mask Request/Reply) * MAY implement (OK) * MUST send a broadcast REQUEST if using this system to set netmask * (OK... we don't use it) * MUST discard received REPLYs if not using this system (OK) * MUST NOT send replies unless specifically made agent for this sort * of thing. (OK) * * * RFC 1812 (IPv4 Router Requirements) Status (even longer): * 4.3.2.1 (Unknown Message Types) * MUST pass messages of unknown type to ICMP user iface or silently discard * them (OK) * 4.3.2.2 (ICMP Message TTL) * MUST initialize TTL when originating an ICMP message (OK) * 4.3.2.3 (Original Message Header) * SHOULD copy as much data from the offending packet as possible without * the length of the ICMP datagram exceeding 576 bytes (OK) * MUST leave original IP header of the offending packet, but we're not * required to undo modifications made (OK) * 4.3.2.4 (Original Message Source Address) * MUST use one of addresses for the interface the orig. packet arrived as * source address (OK) * 4.3.2.5 (TOS and Precedence) * SHOULD leave TOS set to the same value unless the packet would be * discarded for that reason (OK) * MUST use TOS=0 if not possible to leave original value (OK) * MUST leave IP Precedence for Source Quench messages (OK -- not sent * at all) * SHOULD use IP Precedence = 6 (Internetwork Control) or 7 (Network Control) * for all other error messages (OK, we use 6) * MAY allow configuration of IP Precedence (OK -- not done) * MUST leave IP Precedence and TOS for reply messages (OK) * 4.3.2.6 (Source Route) * SHOULD use reverse source route UNLESS sending Parameter Problem on source * routing and UNLESS the packet would be immediately discarded (NOT YET) * 4.3.2.7 (When Not to Send ICMP Errors) * MUST NOT send ICMP errors in reply to: * ICMP errors (OK) * Packets failing IP header validation tests unless otherwise noted (OK) * Broadcast/multicast datagrams (OK) * MAC broadcasts (OK) * Non-initial fragments (OK) * Datagram with a source address that isn't a single host. (OK) * 4.3.2.8 (Rate Limiting) * SHOULD be able to limit error message rate (OK) * SHOULD allow setting of rate limits (OK, in the source) * 4.3.3.1 (Destination Unreachable) * All the rules govern the IP layer, and are dealt with in ip.c, not here. * 4.3.3.2 (Redirect) * MAY ignore ICMP Redirects if running a routing protocol or if forwarding * is enabled on the interface (OK -- ignores) * 4.3.3.3 (Source Quench) * SHOULD NOT originate SQ messages (OK) * MUST be able to limit SQ rate if originates them (OK as we don't * send them) * MAY ignore SQ messages it receives (OK -- we don't) * 4.3.3.4 (Time Exceeded) * Requirements dealt with at IP (generating TIME_EXCEEDED). * 4.3.3.5 (Parameter Problem) * MUST generate these for all errors not covered by other messages (OK) * MUST include original value of the value pointed by (OK) * 4.3.3.6 (Echo Request) * MUST implement echo server function (OK) * MUST process at ER of at least max(576, MTU) (OK) * MAY reject broadcast/multicast ER's (We don't, but that's OK) * SHOULD have a config option for silently ignoring ER's (OK) * MUST have a default value for the above switch = NO (OK) * MUST have application layer interface for Echo Request/Reply (OK) * MUST reply using same source address as the request was sent to. * We're OK for unicast ECHOs, and it doesn't say anything about * how to handle broadcast ones, since it's optional. * MUST copy data from Request to Reply (OK) * SHOULD update Record Route / Timestamp options (??) * MUST use reversed Source Route for Reply if possible (NOT YET) * 4.3.3.7 (Information Request/Reply) * SHOULD NOT originate or respond to these (OK) * 4.3.3.8 (Timestamp / Timestamp Reply) * MAY implement (OK) * MUST reply to every Timestamp message received (OK) * MAY discard broadcast REQUESTs. (OK, but see source for inconsistency) * MUST reply using same source address as the request was sent to. (OK) * MUST use reversed Source Route if possible (NOT YET) * SHOULD update Record Route / Timestamp options (??) * MUST pass REPLYs to transport/user layer (requires RAW, just like * ECHO) (OK) * MUST update clock for timestamp at least 16 times/sec (OK) * MUST be "correct within a few minutes" (OK) * 4.3.3.9 (Address Mask Request/Reply) * MUST have support for receiving AMRq and responding with AMRe (OK, * but only as a compile-time option) * SHOULD have option for each interface for AMRe's, MUST default to * NO (NOT YET) * MUST NOT reply to AMRq before knows the correct AM (OK) * MUST NOT respond to AMRq with source address 0.0.0.0 on physical * interfaces having multiple logical i-faces with different masks * (NOT YET) * SHOULD examine all AMRe's it receives and check them (NOT YET) * SHOULD log invalid AMRe's (AM+sender) (NOT YET) * MUST NOT use contents of AMRe to determine correct AM (OK) * MAY broadcast AMRe's after having configured address masks (OK -- doesn't) * MUST NOT do broadcast AMRe's if not set by extra option (OK, no option) * MUST use the { , -1 } form of broadcast addresses (OK) * 4.3.3.10 (Router Advertisement and Solicitations) * MUST support router part of Router Discovery Protocol on all networks we * support broadcast or multicast addressing. (OK -- done by gated) * MUST have all config parameters with the respective defaults (OK) * 5.2.7.1 (Destination Unreachable) * MUST generate DU's (OK) * SHOULD choose a best-match response code (OK) * SHOULD NOT generate Host Isolated codes (OK) * SHOULD use Communication Administratively Prohibited when administratively * filtering packets (NOT YET -- bug-to-bug compatibility) * MAY include config option for not generating the above and silently * discard the packets instead (OK) * MAY include config option for not generating Precedence Violation and * Precedence Cutoff messages (OK as we don't generate them at all) * MUST use Host Unreachable or Dest. Host Unknown codes whenever other hosts * on the same network might be reachable (OK -- no net unreach's at all) * MUST use new form of Fragmentation Needed and DF Set messages (OK) * 5.2.7.2 (Redirect) * MUST NOT generate network redirects (OK) * MUST be able to generate host redirects (OK) * SHOULD be able to generate Host+TOS redirects (NO as we don't use TOS) * MUST have an option to use Host redirects instead of Host+TOS ones (OK as * no Host+TOS Redirects are used) * MUST NOT generate redirects unless forwarding to the same i-face and the * dest. address is on the same subnet as the src. address and no source * routing is in use. (OK) * MUST NOT follow redirects when using a routing protocol (OK) * MAY use redirects if not using a routing protocol (OK, compile-time option) * MUST comply to Host Requirements when not acting as a router (OK) * 5.2.7.3 (Time Exceeded) * MUST generate Time Exceeded Code 0 when discarding packet due to TTL=0 (OK) * MAY have a per-interface option to disable origination of TE messages, but * it MUST default to "originate" (OK -- we don't support it) */ #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 #ifdef CONFIG_IP_MASQUERADE #include #endif #define min(a,b) ((a)<(b)?(a):(b)) /* * Statistics */ 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, HOS_UNREACH and SR_FAIELD MUST be considered 'transient errs'. */ struct icmp_err icmp_err_convert[] = { { ENETUNREACH, 0 }, /* ICMP_NET_UNREACH */ { EHOSTUNREACH, 0 }, /* ICMP_HOST_UNREACH */ { ENOPROTOOPT, 1 }, /* ICMP_PROT_UNREACH */ { ECONNREFUSED, 1 }, /* ICMP_PORT_UNREACH */ { EMSGSIZE, 0 }, /* ICMP_FRAG_NEEDED */ { EOPNOTSUPP, 0 }, /* ICMP_SR_FAILED */ { ENETUNREACH, 1 }, /* ICMP_NET_UNKNOWN */ { EHOSTDOWN, 1 }, /* ICMP_HOST_UNKNOWN */ { ENONET, 1 }, /* ICMP_HOST_ISOLATED */ { ENETUNREACH, 1 }, /* ICMP_NET_ANO */ { EHOSTUNREACH, 1 }, /* ICMP_HOST_ANO */ { ENETUNREACH, 0 }, /* ICMP_NET_UNR_TOS */ { EHOSTUNREACH, 0 }, /* ICMP_HOST_UNR_TOS */ { EHOSTUNREACH, 1 }, /* ICMP_PKT_FILTERED */ { EHOSTUNREACH, 1 }, /* ICMP_PREC_VIOLATION */ { EHOSTUNREACH, 1 } /* ICMP_PREC_CUTOFF */ }; /* Control parameters for ECHO relies. */ int sysctl_icmp_echo_ignore_all = 0; int sysctl_icmp_echo_ignore_broadcasts = 0; /* Control parameter - ignore bogus broadcast responses? */ int sysctl_icmp_ignore_bogus_error_responses =0; extern int sysctl_ip_always_defrag; /* * ICMP control array. This specifies what to do with each ICMP. */ struct icmp_control { unsigned long *output; /* Address to increment on output */ unsigned long *input; /* Address to increment on input */ void (*handler)(struct icmphdr *icmph, struct sk_buff *skb, int len); short error; /* This ICMP is classed as an error message */ int *timeout; /* Rate limit */ }; static struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; /* * Build xmit assembly blocks */ struct icmp_bxm { void *data_ptr; int data_len; struct icmphdr icmph; unsigned long csum; struct ip_options replyopts; unsigned char optbuf[40]; }; /* * The ICMP socket. 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. */ struct inode icmp_inode; struct socket *icmp_socket=&icmp_inode.u.socket_i; /* * 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. * * 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; 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; return 1; } return 0; } static inline int icmpv4_xrlim_allow(struct rtable *rt, int type, int code) { struct dst_entry *dst = &rt->u.dst; if (type > NR_ICMP_TYPES || !icmp_pointers[type].timeout) return 1; /* Don't limit PMTU discovery. */ if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) return 1; /* Redirect has its own rate limit mechanism */ if (type == ICMP_REDIRECT) return 1; /* No rate limit on loopback */ if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) return 1; return xrlim_allow(dst, *(icmp_pointers[type].timeout)); } /* * Maintain the counters used in the SNMP statistics for outgoing ICMP */ static void icmp_out_count(int type) { if (type>NR_ICMP_TYPES) return; (*icmp_pointers[type].output)++; icmp_statistics.IcmpOutMsgs++; } /* * Checksum each fragment, and on the first include the headers and final checksum. */ static int icmp_glue_bits(const void *p, char *to, unsigned int offset, unsigned int fraglen) { struct icmp_bxm *icmp_param = (struct icmp_bxm *)p; struct icmphdr *icmph; unsigned long csum; if (offset) { icmp_param->csum=csum_partial_copy(icmp_param->data_ptr+offset-sizeof(struct icmphdr), to, fraglen,icmp_param->csum); return 0; } /* * First fragment includes header. Note that we've done * the other fragments first, so that we get the checksum * for the whole packet here. */ csum = csum_partial_copy((void *)&icmp_param->icmph, to, sizeof(struct icmphdr), icmp_param->csum); csum = csum_partial_copy(icmp_param->data_ptr, to+sizeof(struct icmphdr), fraglen-sizeof(struct icmphdr), csum); icmph=(struct icmphdr *)to; icmph->checksum = csum_fold(csum); return 0; } /* * 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 ipcm_cookie ipc; struct rtable *rt = (struct rtable*)skb->dst; u32 daddr; if (ip_options_echo(&icmp_param->replyopts, skb)) return; icmp_param->icmph.checksum=0; icmp_param->csum=0; icmp_out_count(icmp_param->icmph.type); sk->ip_tos = skb->nh.iph->tos; daddr = ipc.addr = rt->rt_src; ipc.opt = &icmp_param->replyopts; if (ipc.opt->srr) daddr = icmp_param->replyopts.faddr; if (ip_route_output(&rt, daddr, rt->rt_spec_dst, RT_TOS(skb->nh.iph->tos), 0)) return; ip_build_xmit(sk, icmp_glue_bits, icmp_param, icmp_param->data_len+sizeof(struct icmphdr), &ipc, rt, MSG_DONTWAIT); ip_rt_put(rt); } /* * 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, unsigned long info) { struct iphdr *iph; struct icmphdr *icmph; int room; struct icmp_bxm icmp_param; struct rtable *rt = (struct rtable*)skb_in->dst; struct ipcm_cookie ipc; u32 saddr; u8 tos; /* * Find the original header */ iph = skb_in->nh.iph; /* * No replies to physical multicast/broadcast */ if (skb_in->pkt_type!=PACKET_HOST) return; /* * Now check at the protocol level */ if (!rt) { if (sysctl_ip_always_defrag == 0 && net_ratelimit()) printk(KERN_DEBUG "icmp_send: destinationless packet\n"); return; } if (rt->rt_flags&(RTCF_BROADCAST|RTCF_MULTICAST)) return; /* * Only reply to fragment 0. We byte re-order the constant * mask for efficiency. */ if (iph->frag_off&htons(IP_OFFSET)) return; /* * 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) { icmph = (struct icmphdr *)((char *)iph + (iph->ihl<<2)); /* * Assume any unknown ICMP type is an error. This isn't * specified by the RFC, but think about it.. */ if (icmph->type>NR_ICMP_TYPES || icmp_pointers[icmph->type].error) return; } } /* * Construct source address and options. */ #ifdef CONFIG_IP_ROUTE_NAT /* * Restore original addresses if packet has been translated. */ if (rt->rt_flags&RTCF_NAT && IPCB(skb_in)->flags&IPSKB_TRANSLATED) { iph->daddr = rt->key.dst; iph->saddr = rt->key.src; } #endif #ifdef CONFIG_IP_MASQUERADE if (type==ICMP_DEST_UNREACH && IPCB(skb_in)->flags&IPSKB_MASQUERADED) { ip_fw_unmasq_icmp(skb_in); } #endif saddr = iph->daddr; if (!(rt->rt_flags & RTCF_LOCAL)) saddr = 0; tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | IPTOS_PREC_INTERNETCONTROL) : iph->tos; /* XXX: use a more aggressive expire for routes created by * this call (not longer than the rate limit timeout). * It could be also worthwhile to not put them into ipv4 * fast routing cache at first. Otherwise an attacker can * grow the routing table. */ if (ip_route_output(&rt, iph->saddr, saddr, RT_TOS(tos), 0)) return; if (ip_options_echo(&icmp_param.replyopts, skb_in)) goto ende; /* * Prepare data for ICMP header. */ icmp_param.icmph.type=type; icmp_param.icmph.code=code; icmp_param.icmph.un.gateway = info; icmp_param.icmph.checksum=0; icmp_param.csum=0; icmp_param.data_ptr=iph; icmp_out_count(icmp_param.icmph.type); icmp_socket->sk->ip_tos = tos; ipc.addr = iph->saddr; ipc.opt = &icmp_param.replyopts; if (icmp_param.replyopts.srr) { ip_rt_put(rt); if (ip_route_output(&rt, icmp_param.replyopts.faddr, saddr, RT_TOS(tos), 0)) return; } if (!icmpv4_xrlim_allow(rt, type, code)) goto ende; /* RFC says return as much as we can without exceeding 576 bytes. */ room = rt->u.dst.pmtu; if (room > 576) room = 576; room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen; room -= sizeof(struct icmphdr); icmp_param.data_len=(iph->ihl<<2)+skb_in->len; if (icmp_param.data_len > room) icmp_param.data_len = room; ip_build_xmit(icmp_socket->sk, icmp_glue_bits, &icmp_param, icmp_param.data_len+sizeof(struct icmphdr), &ipc, rt, MSG_DONTWAIT); ende: ip_rt_put(rt); } /* * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. */ static void icmp_unreach(struct icmphdr *icmph, struct sk_buff *skb, int len) { struct iphdr *iph; int hash; struct inet_protocol *ipprot; unsigned char *dp; struct sock *raw_sk; /* * Incomplete header ? * Only checks for the IP header, there should be an * additional check for longer headers in upper levels. */ if(lentype==ICMP_DEST_UNREACH) { switch(icmph->code & 15) { case ICMP_NET_UNREACH: break; case ICMP_HOST_UNREACH: break; case ICMP_PROT_UNREACH: break; case ICMP_PORT_UNREACH: break; case ICMP_FRAG_NEEDED: if (ipv4_config.no_pmtu_disc) { if (sysctl_ip_always_defrag == 0 && net_ratelimit()) printk(KERN_INFO "ICMP: %d.%d.%d.%d: fragmentation needed and DF set.\n", NIPQUAD(iph->daddr)); } else { unsigned short new_mtu; new_mtu = ip_rt_frag_needed(iph, ntohs(icmph->un.frag.mtu)); if (!new_mtu) return; icmph->un.frag.mtu = htons(new_mtu); } break; case ICMP_SR_FAILED: if (sysctl_ip_always_defrag == 0 && net_ratelimit()) printk(KERN_INFO "ICMP: %d.%d.%d.%d: Source Route Failed.\n", NIPQUAD(iph->daddr)); break; default: break; } if (icmph->code>NR_ICMP_UNREACH) return; } /* * 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) { if (inet_addr_type(iph->daddr) == RTN_BROADCAST) { if (net_ratelimit()) printk(KERN_WARNING "%d.%d.%d.%d sent an invalid ICMP error to a broadcast.\n", NIPQUAD(skb->nh.iph->saddr)); return; } } /* * Deliver ICMP message to raw sockets. Pretty useless feature? */ /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */ hash = iph->protocol & (MAX_INET_PROTOS - 1); if ((raw_sk = raw_v4_htable[hash]) != NULL) { while ((raw_sk = raw_v4_lookup(raw_sk, iph->protocol, iph->saddr, iph->daddr, skb->dev->ifindex)) != NULL) { raw_err(raw_sk, skb); raw_sk = raw_sk->next; } } /* * This can't change while we are doing it. */ ipprot = (struct inet_protocol *) inet_protos[hash]; while(ipprot != NULL) { struct inet_protocol *nextip; nextip = (struct inet_protocol *) ipprot->next; /* * Pass it off to everyone who wants it. */ /* RFC1122: OK. Passes appropriate ICMP errors to the */ /* appropriate protocol layer (MUST), as per 3.2.2. */ if (iph->protocol == ipprot->protocol && ipprot->err_handler) ipprot->err_handler(skb, dp, len); ipprot = nextip; } } /* * Handle ICMP_REDIRECT. */ static void icmp_redirect(struct icmphdr *icmph, struct sk_buff *skb, int len) { struct iphdr *iph; unsigned long ip; if (len < sizeof(struct iphdr)) { icmp_statistics.IcmpInErrors++; return; } /* * Get the copied header of the packet that caused the redirect */ iph = (struct iphdr *) (icmph + 1); ip = iph->daddr; switch(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, icmph->un.gateway, iph->saddr, iph->tos, skb->dev); break; default: break; } } /* * 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 icmphdr *icmph, struct sk_buff *skb, int len) { if (!sysctl_icmp_echo_ignore_all) { struct icmp_bxm icmp_param; icmp_param.icmph=*icmph; icmp_param.icmph.type=ICMP_ECHOREPLY; icmp_param.data_ptr=(icmph+1); icmp_param.data_len=len; 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 icmphdr *icmph, struct sk_buff *skb, int len) { struct timeval tv; __u32 times[3]; /* So the new timestamp works on ALPHA's.. */ struct icmp_bxm icmp_param; /* * Too short. */ if(len<12) { icmp_statistics.IcmpInErrors++; return; } /* * Fill in the current time as ms since midnight UT: */ do_gettimeofday(&tv); times[1] = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000); times[2] = times[1]; memcpy((void *)×[0], icmph+1, 4); /* Incoming stamp */ icmp_param.icmph=*icmph; icmp_param.icmph.type=ICMP_TIMESTAMPREPLY; icmp_param.icmph.code=0; icmp_param.data_ptr=× icmp_param.data_len=12; icmp_reply(&icmp_param, skb); } /* * 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 icmphdr *icmph, struct sk_buff *skb, int len) { #if 0 if (sysctl_ip_always_defrag == 0 && 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 icmphdr *icmph, struct sk_buff *skb, int len) { struct rtable *rt = (struct rtable*)skb->dst; struct device *dev = skb->dev; struct in_device *in_dev = dev->ip_ptr; struct in_ifaddr *ifa; u32 mask; if (!in_dev || !in_dev->ifa_list || !IN_DEV_LOG_MARTIANS(in_dev) || !IN_DEV_FORWARD(in_dev) || len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) return; mask = *(u32*)&icmph[1]; for (ifa=in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { if (mask == ifa->ifa_mask && inet_ifa_match(rt->rt_src, ifa)) return; } if (sysctl_ip_always_defrag == 0 && net_ratelimit()) printk(KERN_INFO "Wrong address mask %08X from %08X/%s\n", ntohl(mask), ntohl(rt->rt_src), dev->name); } static void icmp_discard(struct icmphdr *icmph, struct sk_buff *skb, int len) { } #ifdef CONFIG_IP_TRANSPARENT_PROXY /* * Check incoming icmp packets not addressed locally, to check whether * they relate to a (proxying) socket on our system. * Needed for transparent proxying. * * This code is presently ugly and needs cleanup. * Probably should add a chkaddr entry to ipprot to call a chk routine * in udp.c or tcp.c... */ /* This should work with the new hashes now. -DaveM */ extern struct sock *tcp_v4_lookup(u32 saddr, u16 sport, u32 daddr, u16 dport, int dif); extern struct sock *udp_v4_lookup(u32 saddr, u16 sport, u32 daddr, u16 dport, int dif); int icmp_chkaddr(struct sk_buff *skb) { struct icmphdr *icmph=(struct icmphdr *)(skb->nh.raw + skb->nh.iph->ihl*4); struct iphdr *iph = (struct iphdr *) (icmph + 1); void (*handler)(struct icmphdr *icmph, struct sk_buff *skb, int len) = icmp_pointers[icmph->type].handler; if (handler == icmp_unreach || handler == icmp_redirect) { struct sock *sk; switch (iph->protocol) { case IPPROTO_TCP: { struct tcphdr *th = (struct tcphdr *)(((unsigned char *)iph)+(iph->ihl<<2)); sk = tcp_v4_lookup(iph->daddr, th->dest, iph->saddr, th->source, skb->dev->ifindex); if (!sk || (sk->state == TCP_LISTEN)) return 0; /* * This packet came from us. */ return 1; } case IPPROTO_UDP: { struct udphdr *uh = (struct udphdr *)(((unsigned char *)iph)+(iph->ihl<<2)); sk = udp_v4_lookup(iph->daddr, uh->dest, iph->saddr, uh->source, skb->dev->ifindex); if (!sk) return 0; if (sk->saddr != iph->saddr && inet_addr_type(iph->saddr) != RTN_LOCAL) return 0; /* * This packet may have come from us. * Assume it did. */ return 1; } } } return 0; } #endif /* * Deal with incoming ICMP packets. */ int icmp_rcv(struct sk_buff *skb, unsigned short len) { struct icmphdr *icmph = skb->h.icmph; struct rtable *rt = (struct rtable*)skb->dst; icmp_statistics.IcmpInMsgs++; /* * 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(len < sizeof(struct icmphdr) || ip_compute_csum((unsigned char *) icmph, len) || 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; } } len -= sizeof(struct icmphdr); (*icmp_pointers[icmph->type].input)++; (icmp_pointers[icmph->type].handler)(icmph, skb, len); drop: kfree_skb(skb); return 0; error: icmp_statistics.IcmpInErrors++; goto drop; } /* * A spare long used to speed up statistics updating */ static unsigned long dummy; /* * Configurable rate limits. * Someone should check if these default values are correct. * Note that these values interact with the routing cache GC timeout. * If you chose them too high they won't take effect, because the * dst_entry gets expired too early. The same should happen when * the cache grows too big. */ int sysctl_icmp_destunreach_time = 1*HZ; int sysctl_icmp_timeexceed_time = 1*HZ; int sysctl_icmp_paramprob_time = 1*HZ; int sysctl_icmp_echoreply_time = 0; /* don't limit it per default. */ /* * This table is the definition of how we handle ICMP. */ static struct icmp_control icmp_pointers[NR_ICMP_TYPES+1] = { /* ECHO REPLY (0) */ { &icmp_statistics.IcmpOutEchoReps, &icmp_statistics.IcmpInEchoReps, icmp_discard, 0, &sysctl_icmp_echoreply_time}, { &dummy, &icmp_statistics.IcmpInErrors, icmp_discard, 1, }, { &dummy, &icmp_statistics.IcmpInErrors, icmp_discard, 1, }, /* DEST UNREACH (3) */ { &icmp_statistics.IcmpOutDestUnreachs, &icmp_statistics.IcmpInDestUnreachs, icmp_unreach, 1, &sysctl_icmp_destunreach_time }, /* SOURCE QUENCH (4) */ { &icmp_statistics.IcmpOutSrcQuenchs, &icmp_statistics.IcmpInSrcQuenchs, icmp_unreach, 1, }, /* REDIRECT (5) */ { &icmp_statistics.IcmpOutRedirects, &icmp_statistics.IcmpInRedirects, icmp_redirect, 1, }, { &dummy, &icmp_statistics.IcmpInErrors, icmp_discard, 1, }, { &dummy, &icmp_statistics.IcmpInErrors, icmp_discard, 1, }, /* ECHO (8) */ { &icmp_statistics.IcmpOutEchos, &icmp_statistics.IcmpInEchos, icmp_echo, 0, }, { &dummy, &icmp_statistics.IcmpInErrors, icmp_discard, 1, }, { &dummy, &icmp_statistics.IcmpInErrors, icmp_discard, 1, }, /* TIME EXCEEDED (11) */ { &icmp_statistics.IcmpOutTimeExcds, &icmp_statistics.IcmpInTimeExcds, icmp_unreach, 1, &sysctl_icmp_timeexceed_time }, /* PARAMETER PROBLEM (12) */ { &icmp_statistics.IcmpOutParmProbs, &icmp_statistics.IcmpInParmProbs, icmp_unreach, 1, &sysctl_icmp_paramprob_time }, /* TIMESTAMP (13) */ { &icmp_statistics.IcmpOutTimestamps, &icmp_statistics.IcmpInTimestamps, icmp_timestamp, 0, }, /* TIMESTAMP REPLY (14) */ { &icmp_statistics.IcmpOutTimestampReps, &icmp_statistics.IcmpInTimestampReps, icmp_discard, 0, }, /* INFO (15) */ { &dummy, &dummy, icmp_discard, 0, }, /* INFO REPLY (16) */ { &dummy, &dummy, icmp_discard, 0, }, /* ADDR MASK (17) */ { &icmp_statistics.IcmpOutAddrMasks, &icmp_statistics.IcmpInAddrMasks, icmp_address, 0, }, /* ADDR MASK REPLY (18) */ { &icmp_statistics.IcmpOutAddrMaskReps, &icmp_statistics.IcmpInAddrMaskReps, icmp_address_reply, 0, } }; __initfunc(void icmp_init(struct net_proto_family *ops)) { int err; icmp_inode.i_mode = S_IFSOCK; icmp_inode.i_sock = 1; icmp_inode.i_uid = 0; icmp_inode.i_gid = 0; icmp_socket->inode = &icmp_inode; icmp_socket->state = SS_UNCONNECTED; icmp_socket->type=SOCK_RAW; if ((err=ops->create(icmp_socket, IPPROTO_ICMP))<0) panic("Failed to create the ICMP control socket.\n"); icmp_socket->sk->allocation=GFP_ATOMIC; icmp_socket->sk->num = 256; /* Don't receive any data */ icmp_socket->sk->ip_ttl = MAXTTL; }