308 lines
10 KiB
C
308 lines
10 KiB
C
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/*
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* packet_tr.c - token ring interface code, contributed in May of 1999
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* by Andrew Chittenden
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*/
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#include "dhcpd.h"
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#if defined (HAVE_TR_SUPPORT) && \
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(defined (PACKET_ASSEMBLY) || defined (PACKET_DECODING))
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#include "includes/netinet/ip.h"
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#include "includes/netinet/udp.h"
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#include "includes/netinet/if_ether.h"
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#include "netinet/if_tr.h"
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#include <sys/time.h>
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/*
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* token ring device handling subroutines. These are required as token-ring
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* does not have a simple on-the-wire header but requires the use of
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* source routing
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*/
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static int insert_source_routing PROTO ((struct trh_hdr *trh, struct interface_info* interface));
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static void save_source_routing PROTO ((struct trh_hdr *trh, struct interface_info* interface));
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static void expire_routes PROTO ((void));
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/*
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* As we keep a list of interesting routing information only, a singly
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* linked list is all we need
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*/
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struct routing_entry {
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struct routing_entry *next;
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unsigned char addr[TR_ALEN];
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unsigned char iface[5];
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__u16 rcf; /* route control field */
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__u16 rseg[8]; /* routing registers */
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unsigned long access_time; /* time we last used this entry */
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};
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static struct routing_entry *routing_info = NULL;
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static int routing_timeout = 10;
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static struct timeval routing_timer;
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void assemble_tr_header (interface, buf, bufix, to)
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struct interface_info *interface;
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unsigned char *buf;
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int *bufix;
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struct hardware *to;
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{
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struct trh_hdr *trh;
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int hdr_len;
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struct trllc *llc;
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/* set up the token header */
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trh = (struct trh_hdr *) &buf[*bufix];
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if (interface -> hw_address.hlen == sizeof (trh->saddr))
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memcpy (trh->saddr, interface -> hw_address.haddr,
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sizeof (trh->saddr));
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else
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memset (trh->saddr, 0x00, sizeof (trh->saddr));
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if (to && to -> hlen == 6) /* XXX */
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memcpy (trh->daddr, to -> haddr, sizeof trh->daddr);
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else
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memset (trh->daddr, 0xff, sizeof (trh->daddr));
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hdr_len = insert_source_routing (trh, interface);
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trh->ac = AC;
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trh->fc = LLC_FRAME;
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/* set up the llc header for snap encoding after the tr header */
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llc = (struct trllc *)(buf + *bufix + hdr_len);
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llc->dsap = EXTENDED_SAP;
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llc->ssap = EXTENDED_SAP;
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llc->llc = UI_CMD;
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llc->protid[0] = 0;
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llc->protid[1] = 0;
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llc->protid[2] = 0;
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llc->ethertype = htons(ETHERTYPE_IP);
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hdr_len += sizeof(struct trllc);
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*bufix += hdr_len;
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}
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static unsigned char tr_broadcast[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
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/*
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* decoding the token header is a bit complex as you can see here. It is
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* further complicated by the linux kernel stripping off some valuable
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* information (see comment below) even though we've asked for the raw
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* packets.
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*/
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ssize_t decode_tr_header (interface, buf, bufix, from)
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struct interface_info *interface;
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unsigned char *buf;
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int bufix;
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struct hardware *from;
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{
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struct trh_hdr *trh = (struct trh_hdr *) buf + bufix;
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struct trllc *llc;
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struct ip *ip;
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struct udphdr *udp;
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unsigned int route_len = 0;
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ssize_t hdr_len;
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struct timeval now;
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/* see whether any source routing information has expired */
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gettimeofday(&now, NULL);
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if (routing_timer.tv_sec == 0)
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routing_timer.tv_sec = now.tv_sec + routing_timeout;
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else if ((now.tv_sec - routing_timer.tv_sec) > 0)
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expire_routes();
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/* the kernel might have stripped off the source
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* routing bit. We try a heuristic to determine whether
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* this is the case and put it back on if so
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*/
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route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8;
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llc = (struct trllc *)(buf + bufix + sizeof(struct trh_hdr)-TR_MAXRIFLEN+route_len);
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if (llc->dsap == EXTENDED_SAP
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&& llc->ssap == EXTENDED_SAP
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&& llc->llc == UI_CMD
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&& llc->protid[0] == 0
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&& llc->protid[1] == 0
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&& llc->protid[2] == 0) {
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/* say there is source routing information present */
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trh->saddr[0] |= TR_RII;
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}
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if (trh->saddr[0] & TR_RII)
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route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8;
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else
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route_len = 0;
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hdr_len = sizeof (struct trh_hdr) - TR_MAXRIFLEN + route_len;
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/* now filter out unwanted packets: this is based on the packet
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* filter code in bpf.c */
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llc = (struct trllc *)(buf + bufix + hdr_len);
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ip = (struct ip *) (llc + 1);
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udp = (struct udphdr *) ((unsigned char*) ip + ip->ip_hl * 4);
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/* make sure it is a snap encoded, IP, UDP, unfragmented packet sent
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* to our port */
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if (llc->dsap != EXTENDED_SAP
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|| ntohs(llc->ethertype) != ETHERTYPE_IP
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|| ip->ip_p != IPPROTO_UDP
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|| (ip->ip_off & IP_OFFMASK) != 0
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|| udp->uh_dport != local_port)
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return -1;
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/* only save source routing information for packets from valued hosts */
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save_source_routing(trh, interface);
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return hdr_len + sizeof (struct trllc);
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}
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/* insert_source_routing inserts source route information into the token ring
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* header
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*/
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static int insert_source_routing (trh, interface)
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struct trh_hdr *trh;
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struct interface_info* interface;
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{
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struct routing_entry *rover;
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struct timeval now;
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unsigned int route_len = 0;
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gettimeofday(&now, NULL);
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/* single route broadcasts as per rfc 1042 */
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if (memcmp(trh->daddr, tr_broadcast,TR_ALEN) == 0) {
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trh->saddr[0] |= TR_RII;
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trh->rcf = ((sizeof(trh->rcf)) << 8) & TR_RCF_LEN_MASK;
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trh->rcf |= (TR_RCF_FRAME2K | TR_RCF_LIMITED_BROADCAST);
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trh->rcf = htons(trh->rcf);
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} else {
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/* look for a routing entry */
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for (rover = routing_info; rover != NULL; rover = rover->next) {
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if (memcmp(rover->addr, trh->daddr, TR_ALEN) == 0)
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break;
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}
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if (rover != NULL) {
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/* success: route that frame */
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if ((rover->rcf & TR_RCF_LEN_MASK) >> 8) {
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__u16 rcf = rover->rcf;
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memcpy(trh->rseg,rover->rseg,sizeof(trh->rseg));
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rcf ^= TR_RCF_DIR_BIT;
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rcf &= ~TR_RCF_BROADCAST_MASK;
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trh->rcf = htons(rcf);
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trh->saddr[0] |= TR_RII;
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}
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rover->access_time = now.tv_sec;
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} else {
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/* we don't have any routing information so send a
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* limited broadcast */
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trh->saddr[0] |= TR_RII;
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trh->rcf = ((sizeof(trh->rcf)) << 8) & TR_RCF_LEN_MASK;
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trh->rcf |= (TR_RCF_FRAME2K | TR_RCF_LIMITED_BROADCAST);
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trh->rcf = htons(trh->rcf);
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}
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}
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/* return how much of the header we've actually used */
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if (trh->saddr[0] & TR_RII)
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route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8;
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else
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route_len = 0;
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return sizeof (struct trh_hdr) - TR_MAXRIFLEN + route_len;
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}
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/*
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* save any source routing information
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*/
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static void save_source_routing(trh, interface)
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struct trh_hdr *trh;
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struct interface_info *interface;
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{
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struct routing_entry *rover;
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struct timeval now;
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unsigned char saddr[TR_ALEN];
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__u16 rcf = 0;
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gettimeofday(&now, NULL);
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memcpy(saddr, trh->saddr, sizeof(saddr));
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saddr[0] &= 0x7f; /* strip off source routing present flag */
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/* scan our table to see if we've got it */
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for (rover = routing_info; rover != NULL; rover = rover->next) {
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if (memcmp(&rover->addr[0], &saddr[0], TR_ALEN) == 0)
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break;
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}
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/* found an entry so update it with fresh information */
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if (rover != NULL) {
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if ((trh->saddr[0] & TR_RII)
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&& (((ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8) > 2)) {
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rcf = ntohs(trh->rcf);
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rcf &= ~TR_RCF_BROADCAST_MASK;
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memcpy(rover->rseg, trh->rseg, sizeof(rover->rseg));
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}
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rover->rcf = rcf;
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rover->access_time = now.tv_sec;
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return; /* that's all folks */
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}
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/* no entry found, so create one */
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rover = malloc(sizeof(struct routing_entry));
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if (rover == NULL) {
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fprintf(stderr,
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"%s: unable to save source routing information\n",
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__FILE__);
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return;
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}
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memcpy(rover->addr, saddr, sizeof(rover->addr));
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memcpy(rover->iface, interface->name, 5);
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rover->access_time = now.tv_sec;
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if (trh->saddr[0] & TR_RII) {
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if (((ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8) > 2) {
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rcf = ntohs(trh->rcf);
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rcf &= ~TR_RCF_BROADCAST_MASK;
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memcpy(rover->rseg, trh->rseg, sizeof(rover->rseg));
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}
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rover->rcf = rcf;
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}
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/* insert into list */
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rover->next = routing_info;
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routing_info = rover;
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return;
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}
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/*
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* get rid of old routes
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*/
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static void expire_routes()
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{
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struct routing_entry *rover;
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struct routing_entry **prover = &routing_info;
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struct timeval now;
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gettimeofday(&now, NULL);
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while((rover = *prover) != NULL) {
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if ((now.tv_sec - rover->access_time) > routing_timeout) {
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*prover = rover->next;
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free(rover);
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} else
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prover = &rover->next;
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}
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/* Reset the timer */
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routing_timer.tv_sec = now.tv_sec + routing_timeout;
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routing_timer.tv_usec = now.tv_usec;
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}
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#endif
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