pcap-dag.c revision 147894 
1/*
2 * pcap-dag.c: Packet capture interface for Endace DAG card.
3 *
4 * The functionality of this code attempts to mimic that of pcap-linux as much
5 * as possible.  This code is compiled in several different ways depending on
6 * whether DAG_ONLY and HAVE_DAG_API are defined.  If HAVE_DAG_API is not
7 * defined it should not get compiled in, otherwise if DAG_ONLY is defined then
8 * the 'dag_' function calls are renamed to 'pcap_' equivalents.  If DAG_ONLY
9 * is not defined then nothing is altered - the dag_ functions will be
10 * called as required from their pcap-linux/bpf equivalents.
11 *
12 * Authors: Richard Littin, Sean Irvine ({richard,sean}@reeltwo.com)
13 * Modifications: Jesper Peterson, Koryn Grant <support@endace.com>
14 */
15
16#ifndef lint
17static const char rcsid[] _U_ =
18	"@(#) $Header: /tcpdump/master/libpcap/pcap-dag.c,v 1.21.2.1 2005/05/03 18:54:35 guy Exp $ (LBL)";
19#endif
20
21#ifdef HAVE_CONFIG_H
22#include "config.h"
23#endif
24
25#include <sys/param.h>			/* optionally get BSD define */
26
27#include <stdlib.h>
28#include <string.h>
29#include <errno.h>
30
31#include "pcap-int.h"
32
33#include <ctype.h>
34#include <netinet/in.h>
35#include <sys/mman.h>
36#include <sys/socket.h>
37#include <sys/types.h>
38#include <unistd.h>
39
40struct mbuf;		/* Squelch compiler warnings on some platforms for */
41struct rtentry;		/* declarations in <net/if.h> */
42#include <net/if.h>
43
44#include "dagnew.h"
45#include "dagapi.h"
46
47#define MIN_DAG_SNAPLEN		12
48#define MAX_DAG_SNAPLEN		2040
49#define ATM_CELL_SIZE		52
50#define ATM_HDR_SIZE		4
51
52/* SunATM pseudo header */
53struct sunatm_hdr {
54	unsigned char	flags;		/* destination and traffic type */
55	unsigned char	vpi;		/* VPI */
56	unsigned short	vci;		/* VCI */
57};
58
59typedef struct pcap_dag_node {
60	struct pcap_dag_node *next;
61	pcap_t *p;
62	pid_t pid;
63} pcap_dag_node_t;
64
65static pcap_dag_node_t *pcap_dags = NULL;
66static int atexit_handler_installed = 0;
67static const unsigned short endian_test_word = 0x0100;
68
69#define IS_BIGENDIAN() (*((unsigned char *)&endian_test_word))
70
71/*
72 * Swap byte ordering of unsigned long long timestamp on a big endian
73 * machine.
74 */
75#define SWAP_TS(ull)  ((ull & 0xff00000000000000LL) >> 56) | \
76                      ((ull & 0x00ff000000000000LL) >> 40) | \
77                      ((ull & 0x0000ff0000000000LL) >> 24) | \
78                      ((ull & 0x000000ff00000000LL) >> 8)  | \
79                      ((ull & 0x00000000ff000000LL) << 8)  | \
80                      ((ull & 0x0000000000ff0000LL) << 24) | \
81                      ((ull & 0x000000000000ff00LL) << 40) | \
82                      ((ull & 0x00000000000000ffLL) << 56)
83
84
85#ifdef DAG_ONLY
86/* This code is required when compiling for a DAG device only. */
87#include "pcap-dag.h"
88
89/* Replace dag function names with pcap equivalent. */
90#define dag_open_live pcap_open_live
91#define dag_platform_finddevs pcap_platform_finddevs
92#endif /* DAG_ONLY */
93
94static int dag_setfilter(pcap_t *p, struct bpf_program *fp);
95static int dag_stats(pcap_t *p, struct pcap_stat *ps);
96static int dag_set_datalink(pcap_t *p, int dlt);
97static int dag_get_datalink(pcap_t *p);
98static int dag_setnonblock(pcap_t *p, int nonblock, char *errbuf);
99
100static void
101delete_pcap_dag(pcap_t *p)
102{
103	pcap_dag_node_t *curr = NULL, *prev = NULL;
104
105	for (prev = NULL, curr = pcap_dags; curr != NULL && curr->p != p; prev = curr, curr = curr->next) {
106		/* empty */
107	}
108
109	if (curr != NULL && curr->p == p) {
110		if (prev != NULL) {
111			prev->next = curr->next;
112		} else {
113			pcap_dags = curr->next;
114		}
115	}
116}
117
118/*
119 * Performs a graceful shutdown of the DAG card, frees dynamic memory held
120 * in the pcap_t structure, and closes the file descriptor for the DAG card.
121 */
122
123static void
124dag_platform_close(pcap_t *p)
125{
126
127#ifdef linux
128	if (p != NULL && p->md.device != NULL) {
129		if(dag_stop(p->fd) < 0)
130			fprintf(stderr,"dag_stop %s: %s\n", p->md.device, strerror(errno));
131		if(dag_close(p->fd) < 0)
132			fprintf(stderr,"dag_close %s: %s\n", p->md.device, strerror(errno));
133
134		free(p->md.device);
135	}
136#else
137	if (p != NULL) {
138		if(dag_stop(p->fd) < 0)
139			fprintf(stderr,"dag_stop: %s\n", strerror(errno));
140		if(dag_close(p->fd) < 0)
141			fprintf(stderr,"dag_close: %s\n", strerror(errno));
142	}
143#endif
144	delete_pcap_dag(p);
145	/* Note: don't need to call close(p->fd) here as dag_close(p->fd) does this. */
146}
147
148static void
149atexit_handler(void)
150{
151	while (pcap_dags != NULL) {
152		if (pcap_dags->pid == getpid()) {
153			dag_platform_close(pcap_dags->p);
154		} else {
155			delete_pcap_dag(pcap_dags->p);
156		}
157	}
158}
159
160static int
161new_pcap_dag(pcap_t *p)
162{
163	pcap_dag_node_t *node = NULL;
164
165	if ((node = malloc(sizeof(pcap_dag_node_t))) == NULL) {
166		return -1;
167	}
168
169	if (!atexit_handler_installed) {
170		atexit(atexit_handler);
171		atexit_handler_installed = 1;
172	}
173
174	node->next = pcap_dags;
175	node->p = p;
176	node->pid = getpid();
177
178	pcap_dags = node;
179
180	return 0;
181}
182
183/*
184 *  Read at most max_packets from the capture stream and call the callback
185 *  for each of them. Returns the number of packets handled, -1 if an
186 *  error occured, or -2 if we were told to break out of the loop.
187 */
188static int
189dag_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
190{
191	unsigned int processed = 0;
192	int flags = p->md.dag_offset_flags;
193	unsigned int nonblocking = flags & DAGF_NONBLOCK;
194
195	for (;;)
196	{
197		/* Get the next bufferful of packets (if necessary). */
198		while (p->md.dag_mem_top - p->md.dag_mem_bottom < dag_record_size) {
199
200			/*
201			 * Has "pcap_breakloop()" been called?
202			 */
203			if (p->break_loop) {
204				/*
205				 * Yes - clear the flag that indicates that
206				 * it has, and return -2 to indicate that
207				 * we were told to break out of the loop.
208				 */
209				p->break_loop = 0;
210				return -2;
211			}
212
213			p->md.dag_mem_top = dag_offset(p->fd, &(p->md.dag_mem_bottom), flags);
214			if (nonblocking && (p->md.dag_mem_top - p->md.dag_mem_bottom < dag_record_size))
215			{
216				/* Pcap is configured to process only available packets, and there aren't any. */
217				return 0;
218			}
219		}
220
221		/* Process the packets. */
222		while (p->md.dag_mem_top - p->md.dag_mem_bottom >= dag_record_size) {
223
224			unsigned short packet_len = 0;
225			int caplen = 0;
226			struct pcap_pkthdr	pcap_header;
227
228			dag_record_t *header = (dag_record_t *)(p->md.dag_mem_base + p->md.dag_mem_bottom);
229			u_char *dp = ((u_char *)header) + dag_record_size;
230			unsigned short rlen;
231
232			/*
233			 * Has "pcap_breakloop()" been called?
234			 */
235			if (p->break_loop) {
236				/*
237				 * Yes - clear the flag that indicates that
238				 * it has, and return -2 to indicate that
239				 * we were told to break out of the loop.
240				 */
241				p->break_loop = 0;
242				return -2;
243			}
244
245				rlen = ntohs(header->rlen);
246			if (rlen < dag_record_size)
247			{
248				strncpy(p->errbuf, "dag_read: record too small", PCAP_ERRBUF_SIZE);
249				return -1;
250			}
251			p->md.dag_mem_bottom += rlen;
252
253			switch(header->type) {
254			case TYPE_AAL5:
255			case TYPE_ATM:
256				if (header->type == TYPE_AAL5) {
257						packet_len = ntohs(header->wlen);
258					caplen = rlen - dag_record_size;
259				} else {
260					caplen = packet_len = ATM_CELL_SIZE;
261				}
262				if (p->linktype == DLT_SUNATM) {
263					struct sunatm_hdr *sunatm = (struct sunatm_hdr *)dp;
264					unsigned long rawatm;
265
266						rawatm = ntohl(*((unsigned long *)dp));
267						sunatm->vci = htons((rawatm >>  4) & 0xffff);
268					sunatm->vpi = (rawatm >> 20) & 0x00ff;
269					sunatm->flags = ((header->flags.iface & 1) ? 0x80 : 0x00) |
270						((sunatm->vpi == 0 && sunatm->vci == htons(5)) ? 6 :
271						((sunatm->vpi == 0 && sunatm->vci == htons(16)) ? 5 :
272						((dp[ATM_HDR_SIZE] == 0xaa &&
273							dp[ATM_HDR_SIZE+1] == 0xaa &&
274							dp[ATM_HDR_SIZE+2] == 0x03) ? 2 : 1)));
275
276				} else {
277					packet_len -= ATM_HDR_SIZE;
278					caplen -= ATM_HDR_SIZE;
279					dp += ATM_HDR_SIZE;
280				}
281				break;
282
283			case TYPE_ETH:
284					packet_len = ntohs(header->wlen);
285				packet_len -= (p->md.dag_fcs_bits >> 3);
286				caplen = rlen - dag_record_size - 2;
287				if (caplen > packet_len) {
288					caplen = packet_len;
289				}
290				dp += 2;
291				break;
292
293			case TYPE_HDLC_POS:
294					packet_len = ntohs(header->wlen);
295				packet_len -= (p->md.dag_fcs_bits >> 3);
296				caplen = rlen - dag_record_size;
297				if (caplen > packet_len) {
298					caplen = packet_len;
299				}
300				break;
301			}
302
303			if (caplen > p->snapshot)
304				caplen = p->snapshot;
305
306			/* Count lost packets. */
307			if (header->lctr) {
308				if (p->md.stat.ps_drop > (UINT_MAX - ntohs(header->lctr))) {
309					p->md.stat.ps_drop = UINT_MAX;
310				} else {
311					p->md.stat.ps_drop += ntohs(header->lctr);
312				}
313			}
314
315			/* Run the packet filter if there is one. */
316			if ((p->fcode.bf_insns == NULL) || bpf_filter(p->fcode.bf_insns, dp, packet_len, caplen)) {
317
318				/* convert between timestamp formats */
319				register unsigned long long ts;
320
321				if (IS_BIGENDIAN()) {
322					ts = SWAP_TS(header->ts);
323				} else {
324					ts = header->ts;
325				}
326
327				pcap_header.ts.tv_sec = ts >> 32;
328				ts = (ts & 0xffffffffULL) * 1000000;
329				ts += 0x80000000; /* rounding */
330				pcap_header.ts.tv_usec = ts >> 32;
331				if (pcap_header.ts.tv_usec >= 1000000) {
332					pcap_header.ts.tv_usec -= 1000000;
333					pcap_header.ts.tv_sec++;
334				}
335
336				/* Fill in our own header data */
337				pcap_header.caplen = caplen;
338				pcap_header.len = packet_len;
339
340				/* Count the packet. */
341				p->md.stat.ps_recv++;
342
343				/* Call the user supplied callback function */
344				callback(user, &pcap_header, dp);
345
346				/* Only count packets that pass the filter, for consistency with standard Linux behaviour. */
347				processed++;
348				if (processed == cnt)
349				{
350					/* Reached the user-specified limit. */
351					return cnt;
352				}
353			}
354		}
355
356		if (nonblocking || processed)
357		{
358			return processed;
359		}
360	}
361
362	return processed;
363}
364
365static int
366dag_inject(pcap_t *p, const void *buf _U_, size_t size _U_)
367{
368	strlcpy(p->errbuf, "Sending packets isn't supported on DAG cards",
369	    PCAP_ERRBUF_SIZE);
370	return (-1);
371}
372
373/*
374 *  Get a handle for a live capture from the given DAG device.  Passing a NULL
375 *  device will result in a failure.  The promisc flag is ignored because DAG
376 *  cards are always promiscuous.  The to_ms parameter is also ignored as it is
377 *  not supported in hardware.
378 *
379 *  See also pcap(3).
380 */
381pcap_t *
382dag_open_live(const char *device, int snaplen, int promisc, int to_ms, char *ebuf)
383{
384	char conf[30]; /* dag configure string */
385	pcap_t *handle;
386	char *s;
387	int n;
388	daginf_t* daginf;
389
390	if (device == NULL) {
391		snprintf(ebuf, PCAP_ERRBUF_SIZE, "device is NULL: %s", pcap_strerror(errno));
392		return NULL;
393	}
394	/* Allocate a handle for this session. */
395
396	handle = malloc(sizeof(*handle));
397	if (handle == NULL) {
398		snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc %s: %s", device, pcap_strerror(errno));
399		return NULL;
400	}
401
402	/* Initialize some components of the pcap structure. */
403
404	memset(handle, 0, sizeof(*handle));
405
406	if (strstr(device, "/dev") == NULL) {
407		char * newDev = (char *)malloc(strlen(device) + 6);
408		newDev[0] = '\0';
409		strcat(newDev, "/dev/");
410		strcat(newDev,device);
411		device = newDev;
412	} else {
413		device = strdup(device);
414	}
415
416	if (device == NULL) {
417		snprintf(ebuf, PCAP_ERRBUF_SIZE, "str_dup: %s\n", pcap_strerror(errno));
418		goto fail;
419	}
420
421	/* setup device parameters */
422	if((handle->fd = dag_open((char *)device)) < 0) {
423		snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_open %s: %s", device, pcap_strerror(errno));
424		goto fail;
425	}
426
427	/* set the card snap length to the specified snaplen parameter */
428	if (snaplen == 0 || snaplen > MAX_DAG_SNAPLEN) {
429		snaplen = MAX_DAG_SNAPLEN;
430	} else if (snaplen < MIN_DAG_SNAPLEN) {
431		snaplen = MIN_DAG_SNAPLEN;
432	}
433	/* snap len has to be a multiple of 4 */
434	snprintf(conf, 30, "varlen slen=%d", (snaplen + 3) & ~3);
435
436	if(dag_configure(handle->fd, conf) < 0) {
437		snprintf(ebuf, PCAP_ERRBUF_SIZE,"dag_configure %s: %s\n", device, pcap_strerror(errno));
438		goto fail;
439	}
440
441	if((handle->md.dag_mem_base = dag_mmap(handle->fd)) == MAP_FAILED) {
442		snprintf(ebuf, PCAP_ERRBUF_SIZE,"dag_mmap %s: %s\n", device, pcap_strerror(errno));
443		goto fail;
444	}
445
446	if(dag_start(handle->fd) < 0) {
447		snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_start %s: %s\n", device, pcap_strerror(errno));
448		goto fail;
449	}
450
451	/*
452	 * Important! You have to ensure bottom is properly
453	 * initialized to zero on startup, it won't give you
454	 * a compiler warning if you make this mistake!
455	 */
456	handle->md.dag_mem_bottom = 0;
457	handle->md.dag_mem_top = 0;
458	handle->md.dag_fcs_bits = 32;
459
460	/* Query the card first for special cases. */
461	daginf = dag_info(handle->fd);
462	if ((0x4200 == daginf->device_code) || (0x4230 == daginf->device_code))
463	{
464		/* DAG 4.2S and 4.23S already strip the FCS.  Stripping the final word again truncates the packet. */
465		handle->md.dag_fcs_bits = 0;
466	}
467
468	/* Then allow an environment variable to override. */
469	if ((s = getenv("ERF_FCS_BITS")) != NULL) {
470		if ((n = atoi(s)) == 0 || n == 16|| n == 32) {
471			handle->md.dag_fcs_bits = n;
472		} else {
473			snprintf(ebuf, PCAP_ERRBUF_SIZE,
474				"pcap_open_live %s: bad ERF_FCS_BITS value (%d) in environment\n", device, n);
475			goto fail;
476		}
477	}
478
479	handle->snapshot	= snaplen;
480	/*handle->md.timeout	= to_ms; */
481
482	handle->linktype = -1;
483	if (dag_get_datalink(handle) < 0) {
484		strcpy(ebuf, handle->errbuf);
485		goto fail;
486	}
487
488	handle->bufsize = 0;
489
490	if (new_pcap_dag(handle) < 0) {
491		snprintf(ebuf, PCAP_ERRBUF_SIZE, "new_pcap_dag %s: %s\n", device, pcap_strerror(errno));
492		goto fail;
493	}
494
495	/*
496	 * "select()" and "poll()" don't (yet) work on DAG device descriptors.
497	 */
498	handle->selectable_fd = -1;
499
500#ifdef linux
501	handle->md.device = (char *)device;
502#else
503	free((char *)device);
504	device = NULL;
505#endif
506
507	handle->read_op = dag_read;
508	handle->inject_op = dag_inject;
509	handle->setfilter_op = dag_setfilter;
510	handle->setdirection_op = NULL; /* Not implemented.*/
511	handle->set_datalink_op = dag_set_datalink;
512	handle->getnonblock_op = pcap_getnonblock_fd;
513	handle->setnonblock_op = dag_setnonblock;
514	handle->stats_op = dag_stats;
515	handle->close_op = dag_platform_close;
516
517	return handle;
518
519fail:
520	if (device != NULL) {
521		free((char *)device);
522	}
523	if (handle != NULL) {
524		/*
525		 * Get rid of any link-layer type list we allocated.
526		 */
527		if (handle->dlt_list != NULL) {
528			free(handle->dlt_list);
529		}
530		free(handle);
531	}
532
533	return NULL;
534}
535
536static int
537dag_stats(pcap_t *p, struct pcap_stat *ps) {
538	/* This needs to be filled out correctly.  Hopefully a dagapi call will
539		 provide all necessary information.
540	*/
541	/*p->md.stat.ps_recv = 0;*/
542	/*p->md.stat.ps_drop = 0;*/
543
544	*ps = p->md.stat;
545
546	return 0;
547}
548
549/*
550 * Get from "/proc/dag" all interfaces listed there; if they're
551 * already in the list of interfaces we have, that won't add another
552 * instance, but if they're not, that'll add them.
553 *
554 * We don't bother getting any addresses for them.
555 *
556 * We also don't fail if we couldn't open "/proc/dag"; we just leave
557 * the list of interfaces as is.
558 */
559int
560dag_platform_finddevs(pcap_if_t **devlistp, char *errbuf)
561{
562	FILE *proc_dag_f;
563	char linebuf[512];
564	int linenum;
565	unsigned char *p;
566	char name[512];	/* XXX - pick a size */
567	char *q;
568	int ret = 0;
569
570	/* Quick exit if /proc/dag not readable */
571	proc_dag_f = fopen("/proc/dag", "r");
572	if (proc_dag_f == NULL)
573	{
574		int i;
575		char dev[16] = "dagx";
576
577		for (i = '0'; ret == 0 && i <= '9'; i++) {
578			dev[3] = i;
579			if (pcap_add_if(devlistp, dev, 0, NULL, errbuf) == -1) {
580				/*
581				 * Failure.
582				 */
583				ret = -1;
584			}
585		}
586
587		return (ret);
588	}
589
590	for (linenum = 1; fgets(linebuf, sizeof linebuf, proc_dag_f) != NULL; linenum++) {
591
592		/*
593		 * Skip the first two lines - they're headers.
594		 */
595		if (linenum <= 2)
596			continue;
597
598		p = &linebuf[0];
599
600		if (*p == '\0' || *p == '\n' || *p != 'D')
601			continue;  /* not a Dag line */
602
603		/*
604		 * Get the interface name.
605		 */
606		q = &name[0];
607		while (*p != '\0' && *p != ':') {
608			if (*p != ' ')
609				*q++ = tolower(*p++);
610			else
611				p++;
612		}
613		*q = '\0';
614
615		/*
616		 * Add an entry for this interface, with no addresses.
617		 */
618		p[strlen(p) - 1] = '\0'; /* get rid of \n */
619		if (pcap_add_if(devlistp, name, 0, strdup(p + 2), errbuf) == -1) {
620			/*
621			 * Failure.
622			 */
623			ret = -1;
624			break;
625		}
626	}
627	if (ret != -1) {
628		/*
629		 * Well, we didn't fail for any other reason; did we
630		 * fail due to an error reading the file?
631		 */
632		if (ferror(proc_dag_f)) {
633			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
634				  "Error reading /proc/dag: %s",
635				  pcap_strerror(errno));
636			ret = -1;
637		}
638	}
639
640	(void)fclose(proc_dag_f);
641	return (ret);
642}
643
644/*
645 * Installs the given bpf filter program in the given pcap structure.  There is
646 * no attempt to store the filter in kernel memory as that is not supported
647 * with DAG cards.
648 */
649static int
650dag_setfilter(pcap_t *p, struct bpf_program *fp)
651{
652	if (!p)
653		return -1;
654	if (!fp) {
655		strncpy(p->errbuf, "setfilter: No filter specified",
656			sizeof(p->errbuf));
657		return -1;
658	}
659
660	/* Make our private copy of the filter */
661
662	if (install_bpf_program(p, fp) < 0)
663		return -1;
664
665	p->md.use_bpf = 0;
666
667	return (0);
668}
669
670static int
671dag_set_datalink(pcap_t *p, int dlt)
672{
673	p->linktype = dlt;
674
675	return (0);
676}
677
678static int
679dag_setnonblock(pcap_t *p, int nonblock, char *errbuf)
680{
681	/*
682	 * Set non-blocking mode on the FD.
683	 * XXX - is that necessary?  If not, don't bother calling it,
684	 * and have a "dag_getnonblock()" function that looks at
685	 * "p->md.dag_offset_flags".
686	 */
687	if (pcap_setnonblock_fd(p, nonblock, errbuf) < 0)
688		return (-1);
689
690	if (nonblock) {
691		p->md.dag_offset_flags |= DAGF_NONBLOCK;
692	} else {
693		p->md.dag_offset_flags &= ~DAGF_NONBLOCK;
694	}
695	return (0);
696}
697
698static int
699dag_get_datalink(pcap_t *p)
700{
701	int daglinktype;
702
703	if (p->dlt_list == NULL && (p->dlt_list = malloc(2*sizeof(*(p->dlt_list)))) == NULL) {
704		(void)snprintf(p->errbuf, sizeof(p->errbuf), "malloc: %s", pcap_strerror(errno));
705		return (-1);
706	}
707
708	/* Check the type through a dagapi call. */
709	daglinktype = dag_linktype(p->fd);
710
711	switch(daglinktype) {
712
713	case TYPE_HDLC_POS:
714		if (p->dlt_list != NULL) {
715			p->dlt_count = 2;
716			p->dlt_list[0] = DLT_CHDLC;
717			p->dlt_list[1] = DLT_PPP_SERIAL;
718		}
719		p->linktype = DLT_CHDLC;
720		break;
721
722	case TYPE_ETH:
723		/*
724		 * This is (presumably) a real Ethernet capture; give it a
725		 * link-layer-type list with DLT_EN10MB and DLT_DOCSIS, so
726		 * that an application can let you choose it, in case you're
727		 * capturing DOCSIS traffic that a Cisco Cable Modem
728		 * Termination System is putting out onto an Ethernet (it
729		 * doesn't put an Ethernet header onto the wire, it puts raw
730		 * DOCSIS frames out on the wire inside the low-level
731		 * Ethernet framing).
732		 */
733		if (p->dlt_list != NULL) {
734			p->dlt_count = 2;
735			p->dlt_list[0] = DLT_EN10MB;
736			p->dlt_list[1] = DLT_DOCSIS;
737		}
738		p->linktype = DLT_EN10MB;
739		break;
740
741	case TYPE_AAL5:
742	case TYPE_ATM:
743		if (p->dlt_list != NULL) {
744			p->dlt_count = 2;
745			p->dlt_list[0] = DLT_ATM_RFC1483;
746			p->dlt_list[1] = DLT_SUNATM;
747		}
748		p->linktype = DLT_ATM_RFC1483;
749		break;
750
751
752	case TYPE_LEGACY:
753		p->linktype = DLT_NULL;
754		break;
755
756	default:
757		snprintf(p->errbuf, sizeof(p->errbuf), "unknown DAG linktype %d\n", daglinktype);
758		return (-1);
759
760	}
761
762	return p->linktype;
763}
764