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Diffstat (limited to 'common/tr.c')
-rw-r--r-- | common/tr.c | 331 |
1 files changed, 331 insertions, 0 deletions
diff --git a/common/tr.c b/common/tr.c new file mode 100644 index 0000000..6e05faf --- /dev/null +++ b/common/tr.c @@ -0,0 +1,331 @@ +/* tr.c + + token ring interface support + Contributed in May of 1999 by Andrew Chittenden */ + +/* + * Copyright (c) 2011 by Internet Systems Consortium, Inc. ("ISC") + * Copyright (c) 2004-2007,2009 by Internet Systems Consortium, Inc. ("ISC") + * Copyright (c) 1996-2003 by Internet Software Consortium + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT + * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + * + * Internet Systems Consortium, Inc. + * 950 Charter Street + * Redwood City, CA 94063 + * <info@isc.org> + * https://www.isc.org/ + */ + +#include "dhcpd.h" + +#if defined (HAVE_TR_SUPPORT) && \ + (defined (PACKET_ASSEMBLY) || defined (PACKET_DECODING)) +#include "includes/netinet/ip.h" +#include "includes/netinet/udp.h" +#include "includes/netinet/if_ether.h" +#include "netinet/if_tr.h" +#include <sys/time.h> + +/* + * token ring device handling subroutines. These are required as token-ring + * does not have a simple on-the-wire header but requires the use of + * source routing + */ + +static int insert_source_routing (struct trh_hdr *trh, struct interface_info* interface); +static void save_source_routing (struct trh_hdr *trh, struct interface_info* interface); +static void expire_routes (void); + +/* + * As we keep a list of interesting routing information only, a singly + * linked list is all we need + */ +struct routing_entry { + struct routing_entry *next; + unsigned char addr[TR_ALEN]; + unsigned char iface[5]; + u_int16_t rcf; /* route control field */ + u_int16_t rseg[8]; /* routing registers */ + unsigned long access_time; /* time we last used this entry */ +}; + +static struct routing_entry *routing_info = NULL; + +static int routing_timeout = 10; +static struct timeval routing_timer; + +void assemble_tr_header (interface, buf, bufix, to) + struct interface_info *interface; + unsigned char *buf; + unsigned *bufix; + struct hardware *to; +{ + struct trh_hdr *trh; + int hdr_len; + struct trllc *llc; + + + /* set up the token header */ + trh = (struct trh_hdr *) &buf[*bufix]; + if (interface -> hw_address.hlen - 1 == sizeof (trh->saddr)) + memcpy (trh->saddr, &interface -> hw_address.hbuf [1], + sizeof (trh->saddr)); + else + memset (trh->saddr, 0x00, sizeof (trh->saddr)); + + if (to && to -> hlen == 7) /* XXX */ + memcpy (trh->daddr, &to -> hbuf [1], sizeof trh->daddr); + else + memset (trh->daddr, 0xff, sizeof (trh->daddr)); + + hdr_len = insert_source_routing (trh, interface); + + trh->ac = AC; + trh->fc = LLC_FRAME; + + /* set up the llc header for snap encoding after the tr header */ + llc = (struct trllc *)(buf + *bufix + hdr_len); + llc->dsap = EXTENDED_SAP; + llc->ssap = EXTENDED_SAP; + llc->llc = UI_CMD; + llc->protid[0] = 0; + llc->protid[1] = 0; + llc->protid[2] = 0; + llc->ethertype = htons(ETHERTYPE_IP); + + hdr_len += sizeof(struct trllc); + + *bufix += hdr_len; +} + + +static unsigned char tr_broadcast[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }; + +/* + * decoding the token header is a bit complex as you can see here. It is + * further complicated by the linux kernel stripping off some valuable + * information (see comment below) even though we've asked for the raw + * packets. + */ +ssize_t decode_tr_header (interface, buf, bufix, from) + struct interface_info *interface; + unsigned char *buf; + unsigned bufix; + struct hardware *from; +{ + struct trh_hdr *trh = (struct trh_hdr *) buf + bufix; + struct trllc *llc; + struct ip *ip; + struct udphdr *udp; + unsigned int route_len = 0; + ssize_t hdr_len; + struct timeval now; + + /* see whether any source routing information has expired */ + gettimeofday(&now, NULL); + + if (routing_timer.tv_sec == 0) + routing_timer.tv_sec = now.tv_sec + routing_timeout; + else if ((now.tv_sec - routing_timer.tv_sec) > 0) + expire_routes(); + + /* the kernel might have stripped off the source + * routing bit. We try a heuristic to determine whether + * this is the case and put it back on if so + */ + route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8; + llc = (struct trllc *)(buf + bufix + sizeof(struct trh_hdr)-TR_MAXRIFLEN+route_len); + if (llc->dsap == EXTENDED_SAP + && llc->ssap == EXTENDED_SAP + && llc->llc == UI_CMD + && llc->protid[0] == 0 + && llc->protid[1] == 0 + && llc->protid[2] == 0) { + /* say there is source routing information present */ + trh->saddr[0] |= TR_RII; + } + + if (trh->saddr[0] & TR_RII) + route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8; + else + route_len = 0; + + hdr_len = sizeof (struct trh_hdr) - TR_MAXRIFLEN + route_len; + + /* now filter out unwanted packets: this is based on the packet + * filter code in bpf.c */ + llc = (struct trllc *)(buf + bufix + hdr_len); + ip = (struct ip *) (llc + 1); + udp = (struct udphdr *) ((unsigned char*) ip + IP_HL (ip)); + + /* make sure it is a snap encoded, IP, UDP, unfragmented packet sent + * to our port */ + if (llc->dsap != EXTENDED_SAP + || ntohs(llc->ethertype) != ETHERTYPE_IP + || ip->ip_p != IPPROTO_UDP + || (ntohs (ip->ip_off) & IP_OFFMASK) != 0 + || udp->uh_dport != local_port) + return -1; + + /* only save source routing information for packets from valued hosts */ + save_source_routing(trh, interface); + + return hdr_len + sizeof (struct trllc); +} + +/* insert_source_routing inserts source route information into the token ring + * header + */ +static int insert_source_routing (trh, interface) + struct trh_hdr *trh; + struct interface_info* interface; +{ + struct routing_entry *rover; + struct timeval now; + unsigned int route_len = 0; + + gettimeofday(&now, NULL); + + /* single route broadcasts as per rfc 1042 */ + if (memcmp(trh->daddr, tr_broadcast,TR_ALEN) == 0) { + trh->saddr[0] |= TR_RII; + trh->rcf = ((sizeof(trh->rcf)) << 8) & TR_RCF_LEN_MASK; + trh->rcf |= (TR_RCF_FRAME2K | TR_RCF_LIMITED_BROADCAST); + trh->rcf = htons(trh->rcf); + } else { + /* look for a routing entry */ + for (rover = routing_info; rover != NULL; rover = rover->next) { + if (memcmp(rover->addr, trh->daddr, TR_ALEN) == 0) + break; + } + + if (rover != NULL) { + /* success: route that frame */ + if ((rover->rcf & TR_RCF_LEN_MASK) >> 8) { + u_int16_t rcf = rover->rcf; + memcpy(trh->rseg,rover->rseg,sizeof(trh->rseg)); + rcf ^= TR_RCF_DIR_BIT; + rcf &= ~TR_RCF_BROADCAST_MASK; + trh->rcf = htons(rcf); + trh->saddr[0] |= TR_RII; + } + rover->access_time = now.tv_sec; + } else { + /* we don't have any routing information so send a + * limited broadcast */ + trh->saddr[0] |= TR_RII; + trh->rcf = ((sizeof(trh->rcf)) << 8) & TR_RCF_LEN_MASK; + trh->rcf |= (TR_RCF_FRAME2K | TR_RCF_LIMITED_BROADCAST); + trh->rcf = htons(trh->rcf); + } + } + + /* return how much of the header we've actually used */ + if (trh->saddr[0] & TR_RII) + route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8; + else + route_len = 0; + + return sizeof (struct trh_hdr) - TR_MAXRIFLEN + route_len; +} + +/* + * save any source routing information + */ +static void save_source_routing(trh, interface) + struct trh_hdr *trh; + struct interface_info *interface; +{ + struct routing_entry *rover; + struct timeval now; + unsigned char saddr[TR_ALEN]; + u_int16_t rcf = 0; + + gettimeofday(&now, NULL); + + memcpy(saddr, trh->saddr, sizeof(saddr)); + saddr[0] &= 0x7f; /* strip off source routing present flag */ + + /* scan our table to see if we've got it */ + for (rover = routing_info; rover != NULL; rover = rover->next) { + if (memcmp(&rover->addr[0], &saddr[0], TR_ALEN) == 0) + break; + } + + /* found an entry so update it with fresh information */ + if (rover != NULL) { + if ((trh->saddr[0] & TR_RII) && + ((ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8) > 2) { + rcf = ntohs(trh->rcf); + rcf &= ~TR_RCF_BROADCAST_MASK; + memcpy(rover->rseg, trh->rseg, sizeof(rover->rseg)); + } + rover->rcf = rcf; + rover->access_time = now.tv_sec; + return; /* that's all folks */ + } + + /* no entry found, so create one */ + rover = dmalloc (sizeof (struct routing_entry), MDL); + if (rover == NULL) { + fprintf(stderr, + "%s: unable to save source routing information\n", + __FILE__); + return; + } + + memcpy(rover->addr, saddr, sizeof(rover->addr)); + memcpy(rover->iface, interface->name, 5); + rover->access_time = now.tv_sec; + if (trh->saddr[0] & TR_RII) { + if (((ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8) > 2) { + rcf = ntohs(trh->rcf); + rcf &= ~TR_RCF_BROADCAST_MASK; + memcpy(rover->rseg, trh->rseg, sizeof(rover->rseg)); + } + rover->rcf = rcf; + } + + /* insert into list */ + rover->next = routing_info; + routing_info = rover; + + return; +} + +/* + * get rid of old routes + */ +static void expire_routes() +{ + struct routing_entry *rover; + struct routing_entry **prover = &routing_info; + struct timeval now; + + gettimeofday(&now, NULL); + + while((rover = *prover) != NULL) { + if ((now.tv_sec - rover->access_time) > routing_timeout) { + *prover = rover->next; + dfree (rover, MDL); + } else + prover = &rover->next; + } + + /* Reset the timer */ + routing_timer.tv_sec = now.tv_sec + routing_timeout; + routing_timer.tv_usec = now.tv_usec; +} + +#endif |