X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=secnet.git;a=blobdiff_plain;f=netlink.c;h=2c3d12d4302b00aea1a59d44dbdd3ca130a532fc;hp=6384c02220720721d9f8a123e83d976a0e21c9ac;hb=6e3fd952d7052293905334a3bb3911c775222ea6;hpb=55bc97e626e0f31e04b190528b25c6e026942610 diff --git a/netlink.c b/netlink.c index 6384c02..2c3d12d 100644 --- a/netlink.c +++ b/netlink.c @@ -106,6 +106,12 @@ their use. #include "netlink.h" #include "process.h" +#ifdef NETLINK_DEBUG +#define MDEBUG(...) Message(M_DEBUG, __VA_ARGS__) +#else /* !NETLINK_DEBUG */ +#define MDEBUG(...) ((void)0) +#endif /* !NETLINK_DEBUG */ + #define ICMP_TYPE_ECHO_REPLY 0 #define ICMP_TYPE_UNREACHABLE 3 @@ -120,7 +126,7 @@ their use. #define ICMP_CODE_TTL_EXCEEDED 0 /* Generic IP checksum routine */ -static inline uint16_t ip_csum(uint8_t *iph,int32_t count) +static inline uint16_t ip_csum(const uint8_t *iph,int32_t count) { register uint32_t sum=0; @@ -144,7 +150,7 @@ static inline uint16_t ip_csum(uint8_t *iph,int32_t count) * By Jorge Cwik , adapted for linux by * Arnt Gulbrandsen. */ -static inline uint16_t ip_fast_csum(uint8_t *iph, int32_t ihl) { +static inline uint16_t ip_fast_csum(const uint8_t *iph, int32_t ihl) { uint32_t sum; __asm__ __volatile__( @@ -192,7 +198,11 @@ struct iphdr { uint8_t tos; uint16_t tot_len; uint16_t id; - uint16_t frag_off; + uint16_t frag; +#define IPHDR_FRAG_OFF ((uint16_t)0x1fff) +#define IPHDR_FRAG_MORE ((uint16_t)0x2000) +#define IPHDR_FRAG_DONT ((uint16_t)0x4000) +/* reserved 0x8000 */ uint8_t ttl; uint8_t protocol; uint16_t check; @@ -206,7 +216,7 @@ struct icmphdr { uint8_t type; uint8_t code; uint16_t check; - union { + union icmpinfofield { uint32_t unused; struct { uint8_t pointer; @@ -218,8 +228,14 @@ struct icmphdr { uint16_t id; uint16_t seq; } echo; + struct { + uint16_t unused; + uint16_t mtu; + } fragneeded; } d; }; + +static const union icmpinfofield icmp_noinfo; static void netlink_packet_deliver(struct netlink *st, struct netlink_client *client, @@ -246,7 +262,7 @@ static struct icmphdr *netlink_icmp_tmpl(struct netlink *st, h->iph.tos=0; h->iph.tot_len=htons(len+(h->iph.ihl*4)+8); h->iph.id=0; - h->iph.frag_off=0; + h->iph.frag=0; h->iph.ttl=255; /* XXX should be configurable */ h->iph.protocol=1; h->iph.saddr=htonl(st->secnet_address); @@ -298,14 +314,22 @@ static bool_t netlink_icmp_may_reply(struct buffer_if *buf) icmph=(struct icmphdr *)buf->start; if (iph->protocol==1) { switch(icmph->type) { - case 3: /* Destination unreachable */ - case 11: /* Time Exceeded */ - case 12: /* Parameter Problem */ + /* Based on http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml#icmp-parameters-types + * as retrieved Thu, 20 Mar 2014 00:16:44 +0000. + * Deprecated, reserved, unassigned and experimental + * options are treated as not safe to reply to. + */ + case 0: /* Echo Reply */ + case 8: /* Echo */ + case 13: /* Timestamp */ + case 14: /* Timestamp Reply */ + return True; + default: return False; } } /* How do we spot broadcast destination addresses? */ - if (ntohs(iph->frag_off)&0x1fff) return False; /* Non-initial fragment */ + if (ntohs(iph->frag)&IPHDR_FRAG_OFF) return False; source=ntohl(iph->saddr); if (source==0) return False; if ((source&0xff000000)==0x7f000000) return False; @@ -353,8 +377,8 @@ static uint16_t netlink_icmp_reply_len(struct buffer_if *buf) /* client indicates where the packet we're constructing a response to comes from. NULL indicates the host. */ static void netlink_icmp_simple(struct netlink *st, struct buffer_if *buf, - struct netlink_client *client, - uint8_t type, uint8_t code) + uint8_t type, uint8_t code, + union icmpinfofield info) { struct icmphdr *h; uint16_t len; @@ -363,7 +387,7 @@ static void netlink_icmp_simple(struct netlink *st, struct buffer_if *buf, struct iphdr *iph=(struct iphdr *)buf->start; len=netlink_icmp_reply_len(buf); h=netlink_icmp_tmpl(st,ntohl(iph->saddr),len); - h->type=type; h->code=code; + h->type=type; h->code=code; h->d=info; memcpy(buf_append(&st->icmp,len),buf->start,len); netlink_icmp_csum(h); netlink_packet_deliver(st,NULL,&st->icmp); @@ -409,6 +433,146 @@ static bool_t netlink_check(struct netlink *st, struct buffer_if *buf, #undef BAD } +static const char *fragment_filter_header(uint8_t *base, long *hlp) +{ + const int fixedhl = sizeof(struct iphdr); + long hl = *hlp; + const uint8_t *ipend = base + hl; + uint8_t *op = base + fixedhl; + const uint8_t *ip = op; + + while (ip < ipend) { + uint8_t opt = ip[0]; + int remain = ipend - ip; + if (opt == 0x00) /* End of Options List */ break; + if (opt == 0x01) /* No Operation */ continue; + if (remain < 2) return "IPv4 options truncated at length"; + int optlen = ip[1]; + if (remain < optlen) return "IPv4 options truncated in option"; + if (opt & 0x80) /* copy */ { + memmove(op, ip, optlen); + op += optlen; + } + ip += optlen; + } + while ((hl = (op - base)) & 0x3) + *op++ = 0x00 /* End of Option List */; + ((struct iphdr*)base)->ihl = hl >> 2; + *hlp = hl; + + return 0; +} + +/* Fragment or send ICMP Fragmentation Needed */ +static void netlink_maybe_fragment(struct netlink *st, + netlink_deliver_fn *deliver, + void *deliver_dst, + const char *delivery_name, + int32_t mtu, + uint32_t source, uint32_t dest, + struct buffer_if *buf) +{ + struct iphdr *iph=(struct iphdr*)buf->start; + long hl = iph->ihl*4; + const char *ssource = ipaddr_to_string(source); + + if (buf->size <= mtu) { + deliver(deliver_dst, buf); + return; + } + + MDEBUG("%s: fragmenting %s->%s org.size=%"PRId32"\n", + st->name, ssource, delivery_name, buf->size); + +#define BADFRAG(m, ...) \ + Message(M_WARNING, \ + "%s: fragmenting packet from source %s" \ + " for transmission via %s: " m "\n", \ + st->name, ssource, delivery_name, \ + ## __VA_ARGS__); + + unsigned orig_frag = ntohs(iph->frag); + + if (orig_frag&IPHDR_FRAG_DONT) { + union icmpinfofield info = + { .fragneeded = { .unused = 0, .mtu = htons(mtu) } }; + netlink_icmp_simple(st,buf, + ICMP_TYPE_UNREACHABLE, + ICMP_CODE_FRAGMENTATION_REQUIRED, + info); + BUF_FREE(buf); + return; + } + if (mtu < hl + 8) { + BADFRAG("mtu %"PRId32" too small", mtu); + BUF_FREE(buf); + return; + } + + /* we (ab)use the icmp buffer to stash the original packet */ + struct buffer_if *orig = &st->icmp; + BUF_ALLOC(orig,"netlink_client_deliver fragment orig"); + buffer_copy(orig,buf); + BUF_FREE(buf); + + const uint8_t *startindata = orig->start + hl; + const uint8_t *indata = startindata; + const uint8_t *endindata = orig->start + orig->size; + _Bool filtered = 0; + + for (;;) { + /* compute our fragment offset */ + long dataoffset = indata - startindata + + (orig_frag & IPHDR_FRAG_OFF)*8; + assert(!(dataoffset & 7)); + if (dataoffset > IPHDR_FRAG_OFF*8) { + BADFRAG("ultimate fragment offset out of range"); + break; + } + + BUF_ALLOC(buf,"netlink_client_deliver fragment frag"); + buffer_init(buf,calculate_max_start_pad()); + + /* copy header (possibly filtered); will adjust in a bit */ + struct iphdr *fragh = buf_append(buf, hl); + memcpy(fragh, orig->start, hl); + + /* decide how much payload to copy and copy it */ + long avail = mtu - hl; + long remain = endindata - indata; + long use = avail < remain ? (avail & ~(long)7) : remain; + memcpy(buf_append(buf, use), indata, use); + indata += use; + + _Bool last_frag = indata >= endindata; + + /* adjust the header */ + fragh->tot_len = htons(buf->size); + fragh->frag = + htons((orig_frag & ~IPHDR_FRAG_OFF) | + (last_frag ? 0 : IPHDR_FRAG_MORE) | + (dataoffset >> 3)); + fragh->check = 0; + fragh->check = ip_fast_csum((const void*)fragh, fragh->ihl); + + /* actually send it */ + deliver(deliver_dst, buf); + if (last_frag) + break; + + /* after copying the header for the first frag, + * we filter the header for the remaining frags */ + if (!filtered++) { + const char *bad = fragment_filter_header(orig->start, &hl); + if (bad) { BADFRAG("%s", bad); break; } + } + } + + BUF_FREE(orig); + +#undef BADFRAG +} + /* Deliver a packet _to_ client; used after we have decided * what to do with it (and just to check that the client has * actually registered a delivery function with us). */ @@ -427,10 +591,22 @@ static void netlink_client_deliver(struct netlink *st, BUF_FREE(buf); return; } - client->deliver(client->dst, buf); + netlink_maybe_fragment(st, client->deliver,client->dst,client->name, + client->mtu, source,dest,buf); client->outcount++; } +/* Deliver a packet to the host; used after we have decided that that + * is what to do with it. */ +static void netlink_host_deliver(struct netlink *st, + uint32_t source, uint32_t dest, + struct buffer_if *buf) +{ + netlink_maybe_fragment(st, st->deliver_to_host,st->dst,"(host)", + st->mtu, source,dest,buf); + st->outcount++; +} + /* Deliver a packet. "client" is the _origin_ of the packet, not its destination, and is NULL for packets from the host and packets generated internally in secnet. */ @@ -510,8 +686,7 @@ static void netlink_packet_deliver(struct netlink *st, /* The packet's not going down a tunnel. It might (ought to) be for the host. */ if (ipset_contains_addr(st->networks,dest)) { - st->deliver_to_host(st->dst,buf); - st->outcount++; + netlink_host_deliver(st,source,dest,buf); BUF_ASSERT_FREE(buf); } else { string_t s,d; @@ -520,8 +695,8 @@ static void netlink_packet_deliver(struct netlink *st, Message(M_DEBUG,"%s: don't know where to deliver packet " "(s=%s, d=%s)\n", st->name, s, d); free(s); free(d); - netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE, - ICMP_CODE_NET_UNREACHABLE); + netlink_icmp_simple(st,buf,ICMP_TYPE_UNREACHABLE, + ICMP_CODE_NET_UNREACHABLE, icmp_noinfo); BUF_FREE(buf); } } else { @@ -537,19 +712,20 @@ static void netlink_packet_deliver(struct netlink *st, st->name,s,d); free(s); free(d); - netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE, - ICMP_CODE_NET_PROHIBITED); + netlink_icmp_simple(st,buf,ICMP_TYPE_UNREACHABLE, + ICMP_CODE_NET_PROHIBITED, icmp_noinfo); BUF_FREE(buf); } else { if (best_quality>0) { - /* XXX Fragment if required */ netlink_client_deliver(st,st->routes[best_match], source,dest,buf); BUF_ASSERT_FREE(buf); } else { /* Generate ICMP destination unreachable */ - netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE, - ICMP_CODE_NET_UNREACHABLE); /* client==NULL */ + netlink_icmp_simple(st,buf, + ICMP_TYPE_UNREACHABLE, + ICMP_CODE_NET_UNREACHABLE, + icmp_noinfo); BUF_FREE(buf); } } @@ -569,8 +745,8 @@ static void netlink_packet_forward(struct netlink *st, /* Packet has already been checked */ if (iph->ttl<=1) { /* Generate ICMP time exceeded */ - netlink_icmp_simple(st,buf,client,ICMP_TYPE_TIME_EXCEEDED, - ICMP_CODE_TTL_EXCEEDED); + netlink_icmp_simple(st,buf,ICMP_TYPE_TIME_EXCEEDED, + ICMP_CODE_TTL_EXCEEDED,icmp_noinfo); BUF_FREE(buf); return; } @@ -599,9 +775,12 @@ static void netlink_packet_local(struct netlink *st, } h=(struct icmphdr *)buf->start; - if ((ntohs(h->iph.frag_off)&0xbfff)!=0) { - Message(M_WARNING,"%s: fragmented packet addressed to secnet; " - "ignoring it\n",st->name); + unsigned fraginfo = ntohs(h->iph.frag); + if ((fraginfo&(IPHDR_FRAG_OFF|IPHDR_FRAG_MORE))!=0) { + if (!(fraginfo & IPHDR_FRAG_OFF)) + /* report only for first fragment */ + Message(M_WARNING,"%s: fragmented packet addressed to secnet; " + "ignoring it\n",st->name); BUF_FREE(buf); return; } @@ -624,8 +803,8 @@ static void netlink_packet_local(struct netlink *st, Message(M_WARNING,"%s: unknown incoming ICMP\n",st->name); } else { /* Send ICMP protocol unreachable */ - netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE, - ICMP_CODE_PROTOCOL_UNREACHABLE); + netlink_icmp_simple(st,buf,ICMP_TYPE_UNREACHABLE, + ICMP_CODE_PROTOCOL_UNREACHABLE,icmp_noinfo); BUF_FREE(buf); return; } @@ -697,7 +876,7 @@ static void netlink_incoming(struct netlink *st, struct netlink_client *client, address validity and generate ICMP, etc. */ if (st->ptp) { if (client) { - st->deliver_to_host(st->dst,buf); + netlink_host_deliver(st,source,dest,buf); } else { netlink_client_deliver(st,st->clients,source,dest,buf); } @@ -765,7 +944,7 @@ static void netlink_dump_routes(struct netlink *st, bool_t requested) if (requested) c=M_WARNING; if (st->ptp) { net=ipaddr_to_string(st->secnet_address); - Message(c,"%s: point-to-point (remote end is %s); routes:\n", + Message(c,"%s: point-to-point (remote end is %s); routes: ", st->name, net); free(net); netlink_output_subnets(st,c,st->clients->subnets); @@ -1030,7 +1209,7 @@ netlink_deliver_fn *netlink_init(struct netlink *st, though, and will make the route dump look complicated... */ st->subnets=ipset_to_subnet_list(st->networks); st->mtu=dict_read_number(dict, "mtu", False, "netlink", loc, DEFAULT_MTU); - buffer_new(&st->icmp,ICMP_BUFSIZE); + buffer_new(&st->icmp,MAX(ICMP_BUFSIZE,st->mtu)); st->outcount=0; st->localcount=0;