Edit
IABSD.fr/src/lib/libpcap/pcap-bpf.c
guenther
- lib/libpcap/pcap-bpf.c
-
/* $OpenBSD: pcap-bpf.c,v 1.39 2023/03/08 04:43:05 guenther Exp $ */ /* * Copyright (c) 1993, 1994, 1995, 1996, 1998 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that: (1) source code distributions * retain the above copyright notice and this paragraph in its entirety, (2) * distributions including binary code include the above copyright notice and * this paragraph in its entirety in the documentation or other materials * provided with the distribution, and (3) all advertising materials mentioning * features or use of this software display the following acknowledgement: * ``This product includes software developed by the University of California, * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of * the University nor the names of its contributors may be used to endorse * or promote products derived from this software without specific prior * written permission. * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. */ #include <sys/time.h> #include <sys/socket.h> #include <sys/ioctl.h> #include <net/if.h> #include <ctype.h> #include <errno.h> #include <fcntl.h> #include <netdb.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <net/if_media.h> #include "pcap-int.h" #ifdef HAVE_OS_PROTO_H #include "os-proto.h" #endif #include "gencode.h" static int find_802_11(struct bpf_dltlist *); static int monitor_mode(pcap_t *, int); int pcap_stats(pcap_t *p, struct pcap_stat *ps) { struct bpf_stat s; if (ioctl(p->fd, BIOCGSTATS, (caddr_t)&s) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGSTATS: %s", pcap_strerror(errno)); return (PCAP_ERROR); } ps->ps_recv = s.bs_recv; ps->ps_drop = s.bs_drop; return (0); } int pcap_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user) { int cc; int n = 0; u_char *bp, *ep; again: /* * Has "pcap_breakloop()" been called? */ if (p->break_loop) { /* * Yes - clear the flag that indicates that it * has, and return PCAP_ERROR_BREAK to indicate * that we were told to break out of the loop. */ p->break_loop = 0; return (PCAP_ERROR_BREAK); } cc = p->cc; if (p->cc == 0) { cc = read(p->fd, (char *)p->buffer, p->bufsize); if (cc == -1) { /* Don't choke when we get ptraced */ switch (errno) { case EINTR: goto again; case EWOULDBLOCK: return (0); case ENXIO: /* * The device on which we're capturing * went away. * * XXX - we should really return * PCAP_ERROR_IFACE_NOT_UP, but * pcap_dispatch() etc. aren't * defined to return that. */ snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "The interface went down"); return (PCAP_ERROR); } snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "read: %s", pcap_strerror(errno)); return (PCAP_ERROR); } bp = p->buffer; } else bp = p->bp; /* * Loop through each packet. */ #define bhp ((struct bpf_hdr *)bp) ep = bp + cc; while (bp < ep) { int caplen, hdrlen; /* * Has "pcap_breakloop()" been called? * If so, return immediately - if we haven't read any * packets, clear the flag and return PCAP_ERROR_BREAK * to indicate that we were told to break out of the loop, * otherwise leave the flag set, so that the *next* call * will break out of the loop without having read any * packets, and return the number of packets we've * processed so far. */ if (p->break_loop) { p->bp = bp; p->cc = ep - bp; /* * ep is set based on the return value of read(), * but read() from a BPF device doesn't necessarily * return a value that's a multiple of the alignment * value for BPF_WORDALIGN(). However, whenever we * increment bp, we round up the increment value by * a value rounded up by BPF_WORDALIGN(), so we * could increment bp past ep after processing the * last packet in the buffer. * * We treat ep < bp as an indication that this * happened, and just set p->cc to 0. */ if (p->cc < 0) p->cc = 0; if (n == 0) { p->break_loop = 0; return (PCAP_ERROR_BREAK); } else return (n); } caplen = bhp->bh_caplen; hdrlen = bhp->bh_hdrlen; /* * XXX A bpf_hdr matches a pcap_pkthdr. */ (*callback)(user, (struct pcap_pkthdr*)bp, bp + hdrlen); bp += BPF_WORDALIGN(caplen + hdrlen); if (++n >= cnt && cnt > 0) { p->bp = bp; p->cc = ep - bp; return (n); } } #undef bhp p->cc = 0; return (n); } int pcap_inject(pcap_t *p, const void *buf, size_t len) { return (write(p->fd, buf, len)); } int pcap_sendpacket(pcap_t *p, const u_char *buf, int size) { return (pcap_inject(p, buf, size) == -1 ? -1 : 0); } static __inline int bpf_open(pcap_t *p) { int fd; fd = open("/dev/bpf", O_RDWR); if (fd == -1 && errno == EACCES) fd = open("/dev/bpf", O_RDONLY); if (fd == -1) { if (errno == EACCES) fd = PCAP_ERROR_PERM_DENIED; else fd = PCAP_ERROR; snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "(cannot open BPF device): %s", pcap_strerror(errno)); } return (fd); } static int get_dlt_list(int fd, int v, struct bpf_dltlist *bdlp, char *ebuf) { memset(bdlp, 0, sizeof(*bdlp)); if (ioctl(fd, BIOCGDLTLIST, (caddr_t)bdlp) == 0) { bdlp->bfl_list = calloc(bdlp->bfl_len + 1, sizeof(u_int)); if (bdlp->bfl_list == NULL) { (void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); return (PCAP_ERROR); } if (ioctl(fd, BIOCGDLTLIST, (caddr_t)bdlp) == -1) { (void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLTLIST: %s", pcap_strerror(errno)); free(bdlp->bfl_list); return (PCAP_ERROR); } } else { /* * EINVAL just means "we don't support this ioctl on * this device"; don't treat it as an error. */ if (errno != EINVAL) { (void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLTLIST: %s", pcap_strerror(errno)); return (PCAP_ERROR); } } return (0); } /* * Returns 1 if rfmon mode can be set on the pcap_t, 0 if it can't, * a PCAP_ERROR value on an error. */ int pcap_can_set_rfmon(pcap_t *p) { #if defined(HAVE_BSD_IEEE80211) int ret; ret = monitor_mode(p, 0); if (ret == PCAP_ERROR_RFMON_NOTSUP) return (0); /* not an error, just a "can't do" */ if (ret == 0) return (1); /* success */ return (ret); #else return (0); #endif } static void pcap_cleanup_bpf(pcap_t *p) { #ifdef HAVE_BSD_IEEE80211 int sock; struct ifmediareq req; struct ifreq ifr; #endif if (p->md.must_do_on_close != 0) { /* * There's something we have to do when closing this * pcap_t. */ #ifdef HAVE_BSD_IEEE80211 if (p->md.must_do_on_close & MUST_CLEAR_RFMON) { /* * We put the interface into rfmon mode; * take it out of rfmon mode. * * XXX - if somebody else wants it in rfmon * mode, this code cannot know that, so it'll take * it out of rfmon mode. */ sock = socket(AF_INET, SOCK_DGRAM, 0); if (sock == -1) { fprintf(stderr, "Can't restore interface flags (socket() failed: %s).\n" "Please adjust manually.\n", strerror(errno)); } else { memset(&req, 0, sizeof(req)); (void)strlcpy(req.ifm_name, p->opt.source, sizeof(req.ifm_name)); if (ioctl(sock, SIOCGIFMEDIA, &req) == -1) { fprintf(stderr, "Can't restore interface flags " "(SIOCGIFMEDIA failed: %s).\n" "Please adjust manually.\n", strerror(errno)); } else if (req.ifm_current & IFM_IEEE80211_MONITOR) { /* * Rfmon mode is currently on; * turn it off. */ memset(&ifr, 0, sizeof(ifr)); (void)strlcpy(ifr.ifr_name, p->opt.source, sizeof(ifr.ifr_name)); ifr.ifr_media = req.ifm_current & ~IFM_IEEE80211_MONITOR; if (ioctl(sock, SIOCSIFMEDIA, &ifr) == -1) { fprintf(stderr, "Can't restore interface flags " "(SIOCSIFMEDIA failed: %s).\n" "Please adjust manually.\n", strerror(errno)); } } close(sock); } } #endif /* HAVE_BSD_IEEE80211 */ /* * Take this pcap out of the list of pcaps for which we * have to take the interface out of some mode. */ pcap_remove_from_pcaps_to_close(p); p->md.must_do_on_close = 0; } /*XXX*/ if (p->fd >= 0) { close(p->fd); p->fd = -1; } if (p->sf.rfile != NULL) { (void)fclose(p->sf.rfile); free(p->sf.base); } else free(p->buffer); pcap_freecode(&p->fcode); if (p->dlt_list != NULL) { free(p->dlt_list); p->dlt_list = NULL; p->dlt_count = 0; } } void pcap_close(pcap_t *p) { pcap_cleanup_bpf(p); free(p->opt.source); free(p); } static int check_setif_failure(pcap_t *p, int error) { if (error == ENXIO) { /* * No such device. */ snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETIF failed: %s", pcap_strerror(errno)); return (PCAP_ERROR_NO_SUCH_DEVICE); } else if (errno == ENETDOWN) { /* * Return a "network down" indication, so that * the application can report that rather than * saying we had a mysterious failure and * suggest that they report a problem to the * libpcap developers. */ return (PCAP_ERROR_IFACE_NOT_UP); } else { /* * Some other error; fill in the error string, and * return PCAP_ERROR. */ snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETIF: %s: %s", p->opt.source, pcap_strerror(errno)); return (PCAP_ERROR); } } int pcap_activate(pcap_t *p) { int status = 0; int fd; struct ifreq ifr; struct bpf_version bv; struct bpf_dltlist bdl; int new_dlt; u_int v; fd = bpf_open(p); if (fd < 0) { status = fd; goto bad; } p->fd = fd; if (ioctl(fd, BIOCVERSION, (caddr_t)&bv) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCVERSION: %s", pcap_strerror(errno)); status = PCAP_ERROR; goto bad; } if (bv.bv_major != BPF_MAJOR_VERSION || bv.bv_minor < BPF_MINOR_VERSION) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "kernel bpf filter out of date"); status = PCAP_ERROR; goto bad; } #if 0 /* Just use the kernel default */ v = 32768; /* XXX this should be a user-accessible hook */ /* Ignore the return value - this is because the call fails on * BPF systems that don't have kernel malloc. And if the call * fails, it's no big deal, we just continue to use the standard * buffer size. */ (void) ioctl(fd, BIOCSBLEN, (caddr_t)&v); #endif /* * Set the buffer size. */ if (p->opt.buffer_size != 0) { /* * A buffer size was explicitly specified; use it. */ if (ioctl(fd, BIOCSBLEN, (caddr_t)&p->opt.buffer_size) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSBLEN: %s: %s", p->opt.source, pcap_strerror(errno)); status = PCAP_ERROR; goto bad; } } /* * Now bind to the device. */ (void)strlcpy(ifr.ifr_name, p->opt.source, sizeof(ifr.ifr_name)); if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) == -1) { status = check_setif_failure(p, errno); goto bad; } /* Get the data link layer type. */ if (ioctl(fd, BIOCGDLT, (caddr_t)&v) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGDLT: %s", pcap_strerror(errno)); status = PCAP_ERROR; goto bad; } /* * We know the default link type -- now determine all the DLTs * this interface supports. If this fails with EINVAL, it's * not fatal; we just don't get to use the feature later. */ if (get_dlt_list(fd, v, &bdl, p->errbuf) == -1) { status = PCAP_ERROR; goto bad; } p->dlt_count = bdl.bfl_len; p->dlt_list = bdl.bfl_list; /* * *BSD with the new 802.11 ioctls. * Do we want monitor mode? */ if (p->opt.rfmon) { /* * Try to put the interface into monitor mode. */ status = monitor_mode(p, 1); if (status != 0) { /* * We failed. */ goto bad; } /* * We're in monitor mode. * Try to find the best 802.11 DLT_ value and, if we * succeed, try to switch to that mode if we're not * already in that mode. */ new_dlt = find_802_11(&bdl); if (new_dlt != -1) { /* * We have at least one 802.11 DLT_ value. * new_dlt is the best of the 802.11 * DLT_ values in the list. * * If the new mode we want isn't the default mode, * attempt to select the new mode. */ if (new_dlt != v) { if (ioctl(p->fd, BIOCSDLT, &new_dlt) != -1) { /* * We succeeded; make this the * new DLT_ value. */ v = new_dlt; } } } } p->linktype = v; /* set timeout */ if (p->md.timeout) { struct timeval to; to.tv_sec = p->md.timeout / 1000; to.tv_usec = (p->md.timeout * 1000) % 1000000; if (ioctl(p->fd, BIOCSRTIMEOUT, (caddr_t)&to) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT: %s", pcap_strerror(errno)); status = PCAP_ERROR; goto bad; } } if (p->opt.immediate) { v = 1; if (ioctl(p->fd, BIOCIMMEDIATE, &v) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCIMMEDIATE: %s", pcap_strerror(errno)); status = PCAP_ERROR; goto bad; } } if (p->opt.promisc) { /* set promiscuous mode, just warn if it fails */ if (ioctl(p->fd, BIOCPROMISC, NULL) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCPROMISC: %s", pcap_strerror(errno)); status = PCAP_WARNING_PROMISC_NOTSUP; } } if (ioctl(fd, BIOCGBLEN, (caddr_t)&v) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGBLEN: %s", pcap_strerror(errno)); status = PCAP_ERROR; goto bad; } p->bufsize = v; p->buffer = malloc(p->bufsize); if (p->buffer == NULL) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); status = PCAP_ERROR; goto bad; } if (status < 0) goto bad; p->activated = 1; return (status); bad: pcap_cleanup_bpf(p); if (p->errbuf[0] == '\0') { /* * No error message supplied by the activate routine; * for the benefit of programs that don't specially * handle errors other than PCAP_ERROR, return the * error message corresponding to the status. */ snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "%s", pcap_statustostr(status)); } return (status); } static int monitor_mode(pcap_t *p, int set) { int sock; struct ifmediareq req; uint64_t *media_list; int i; int can_do; struct ifreq ifr; sock = socket(AF_INET, SOCK_DGRAM, 0); if (sock == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "can't open socket: %s", pcap_strerror(errno)); return (PCAP_ERROR); } memset(&req, 0, sizeof req); (void)strlcpy(req.ifm_name, p->opt.source, sizeof req.ifm_name); /* * Find out how many media types we have. */ if (ioctl(sock, SIOCGIFMEDIA, &req) == -1) { /* * Can't get the media types. */ switch (errno) { case ENXIO: /* * There's no such device. */ close(sock); return (PCAP_ERROR_NO_SUCH_DEVICE); case EINVAL: case ENOTTY: /* * Interface doesn't support SIOC{G,S}IFMEDIA. */ close(sock); return (PCAP_ERROR_RFMON_NOTSUP); default: snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "SIOCGIFMEDIA 1: %s", pcap_strerror(errno)); close(sock); return (PCAP_ERROR); } } if (req.ifm_count == 0) { /* * No media types. */ close(sock); return (PCAP_ERROR_RFMON_NOTSUP); } /* * Allocate a buffer to hold all the media types, and * get the media types. */ media_list = calloc(req.ifm_count, sizeof(*media_list)); if (media_list == NULL) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); close(sock); return (PCAP_ERROR); } req.ifm_ulist = media_list; if (ioctl(sock, SIOCGIFMEDIA, &req) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "SIOCGIFMEDIA: %s", pcap_strerror(errno)); free(media_list); close(sock); return (PCAP_ERROR); } /* * Look for an 802.11 "automatic" media type. * We assume that all 802.11 adapters have that media type, * and that it will carry the monitor mode supported flag. */ can_do = 0; for (i = 0; i < req.ifm_count; i++) { if (IFM_TYPE(media_list[i]) == IFM_IEEE80211 && IFM_SUBTYPE(media_list[i]) == IFM_AUTO) { /* OK, does it do monitor mode? */ if (media_list[i] & IFM_IEEE80211_MONITOR) { can_do = 1; break; } } } free(media_list); if (!can_do) { /* * This adapter doesn't support monitor mode. */ close(sock); return (PCAP_ERROR_RFMON_NOTSUP); } if (set) { /* * Don't just check whether we can enable monitor mode, * do so, if it's not already enabled. */ if ((req.ifm_current & IFM_IEEE80211_MONITOR) == 0) { /* * Monitor mode isn't currently on, so turn it on, * and remember that we should turn it off when the * pcap_t is closed. */ /* * If we haven't already done so, arrange to have * "pcap_close_all()" called when we exit. */ if (!pcap_do_addexit(p)) { /* * "atexit()" failed; don't put the interface * in monitor mode, just give up. */ snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "atexit failed"); close(sock); return (PCAP_ERROR); } memset(&ifr, 0, sizeof(ifr)); (void)strlcpy(ifr.ifr_name, p->opt.source, sizeof(ifr.ifr_name)); ifr.ifr_media = req.ifm_current | IFM_IEEE80211_MONITOR; if (ioctl(sock, SIOCSIFMEDIA, &ifr) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "SIOCSIFMEDIA: %s", pcap_strerror(errno)); close(sock); return (PCAP_ERROR); } p->md.must_do_on_close |= MUST_CLEAR_RFMON; /* * Add this to the list of pcaps to close when we exit. */ pcap_add_to_pcaps_to_close(p); } } return (0); } /* * Check whether we have any 802.11 link-layer types; return the best * of the 802.11 link-layer types if we find one, and return -1 * otherwise. * * DLT_IEEE802_11_RADIO, with the radiotap header, is considered the * best 802.11 link-layer type; any of the other 802.11-plus-radio * headers are second-best; 802.11 with no radio information is * the least good. */ static int find_802_11(struct bpf_dltlist *bdlp) { int new_dlt; int i; /* * Scan the list of DLT_ values, looking for 802.11 values, * and, if we find any, choose the best of them. */ new_dlt = -1; for (i = 0; i < bdlp->bfl_len; i++) { switch (bdlp->bfl_list[i]) { case DLT_IEEE802_11: /* * 802.11, but no radio. * * Offer this, and select it as the new mode * unless we've already found an 802.11 * header with radio information. */ if (new_dlt == -1) new_dlt = bdlp->bfl_list[i]; break; case DLT_IEEE802_11_RADIO: /* * 802.11 with radiotap. * * Offer this, and select it as the new mode. */ new_dlt = bdlp->bfl_list[i]; break; default: /* * Not 802.11. */ break; } } return (new_dlt); } pcap_t * pcap_create(const char *device, char *errbuf) { pcap_t *p; p = calloc(1, sizeof(*p)); if (p == NULL) { snprintf(errbuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); return (NULL); } p->fd = -1; /* not opened yet */ p->opt.source = strdup(device); if (p->opt.source == NULL) { snprintf(errbuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); free(p); return (NULL); } /* put in some defaults*/ pcap_set_timeout(p, 0); pcap_set_snaplen(p, 65535); /* max packet size */ p->opt.promisc = 0; p->opt.buffer_size = 0; p->opt.immediate = 0; return (p); } pcap_t * pcap_open_live(const char *source, int snaplen, int promisc, int to_ms, char *errbuf) { pcap_t *p; int status; p = pcap_create(source, errbuf); if (p == NULL) return (NULL); status = pcap_set_snaplen(p, snaplen); if (status < 0) goto fail; status = pcap_set_promisc(p, promisc); if (status < 0) goto fail; status = pcap_set_timeout(p, to_ms); if (status < 0) goto fail; /* * Mark this as opened with pcap_open_live(), so that, for * example, we show the full list of DLT_ values, rather * than just the ones that are compatible with capturing * when not in monitor mode. That allows existing applications * to work the way they used to work, but allows new applications * that know about the new open API to, for example, find out the * DLT_ values that they can select without changing whether * the adapter is in monitor mode or not. */ p->oldstyle = 1; status = pcap_activate(p); if (status < 0) goto fail; return (p); fail: if (status == PCAP_ERROR) snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", source, p->errbuf); else if (status == PCAP_ERROR_NO_SUCH_DEVICE || status == PCAP_ERROR_PERM_DENIED || status == PCAP_ERROR_PROMISC_PERM_DENIED) snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s (%s)", source, pcap_statustostr(status), p->errbuf); else snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", source, pcap_statustostr(status)); pcap_close(p); return (NULL); } int pcap_setfilter(pcap_t *p, struct bpf_program *fp) { /* * It looks that BPF code generated by gen_protochain() is not * compatible with some of kernel BPF code (for example BSD/OS 3.1). * Take a safer side for now. */ if (no_optimize || (p->sf.rfile != NULL)){ if (p->fcode.bf_insns != NULL) pcap_freecode(&p->fcode); p->fcode.bf_len = fp->bf_len; p->fcode.bf_insns = reallocarray(NULL, fp->bf_len, sizeof(*fp->bf_insns)); if (p->fcode.bf_insns == NULL) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); return (-1); } memcpy(p->fcode.bf_insns, fp->bf_insns, fp->bf_len * sizeof(*fp->bf_insns)); } else if (ioctl(p->fd, BIOCSETF, (caddr_t)fp) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETF: %s", pcap_strerror(errno)); return (-1); } return (0); } int pcap_setdirection(pcap_t *p, pcap_direction_t d) { u_int dirfilt; switch (d) { case PCAP_D_INOUT: dirfilt = 0; break; case PCAP_D_IN: dirfilt = BPF_DIRECTION_OUT; break; case PCAP_D_OUT: dirfilt = BPF_DIRECTION_IN; break; default: snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "Invalid direction"); return (-1); } if (ioctl(p->fd, BIOCSDIRFILT, &dirfilt) == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSDIRFILT: %s", pcap_strerror(errno)); return (-1); } return (0); } int pcap_set_datalink(pcap_t *p, int dlt) { int i; if (p->dlt_count == 0) { /* * We couldn't fetch the list of DLTs, or we don't * have a "set datalink" operation, which means * this platform doesn't support changing the * DLT for an interface. Check whether the new * DLT is the one this interface supports. */ if (p->linktype != dlt) goto unsupported; /* * It is, so there's nothing we need to do here. */ return (0); } for (i = 0; i < p->dlt_count; i++) if (p->dlt_list[i] == dlt) break; if (i >= p->dlt_count) goto unsupported; if (ioctl(p->fd, BIOCSDLT, &dlt) == -1) { (void) snprintf(p->errbuf, sizeof(p->errbuf), "Cannot set DLT %d: %s", dlt, strerror(errno)); return (-1); } p->linktype = dlt; return (0); unsupported: (void) snprintf(p->errbuf, sizeof(p->errbuf), "DLT %d is not one of the DLTs supported by this device", dlt); return (-1); }