/* * 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. */ #ifndef lint static const char rcsid[] _U_ = "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.67.2.4 2003/11/22 00:06:28 guy Exp $ (LBL)"; #endif #ifdef HAVE_CONFIG_H #include "config.h" #endif #include /* optionally get BSD define */ #include #include #include #include #include #include #include #ifdef _AIX /* * Make "pcap.h" not include "pcap-bpf.h"; we are going to include the * native OS version, as we need "struct bpf_config" from it. */ #define PCAP_DONT_INCLUDE_PCAP_BPF_H #include /* * Prevent bpf.h from redefining the DLT_ values to their * IFT_ values, as we're going to return the standard libpcap * values, not IBM's non-standard IFT_ values. */ #undef _AIX #include #define _AIX #include /* for IFT_ values */ #include #include #include #include #ifdef __64BIT__ #define domakedev makedev64 #define getmajor major64 #define bpf_hdr bpf_hdr32 #else /* __64BIT__ */ #define domakedev makedev #define getmajor major #endif /* __64BIT__ */ #define BPF_NAME "bpf" #define BPF_MINORS 4 #define DRIVER_PATH "/usr/lib/drivers" #define BPF_NODE "/dev/bpf" static int bpfloadedflag = 0; static int odmlockid = 0; #else /* _AIX */ #include #endif /* _AIX */ #include #include #include #include #include #include #include #include "pcap-int.h" #ifdef HAVE_DAG_API #include "pcap-dag.h" #endif /* HAVE_DAG_API */ #ifdef HAVE_OS_PROTO_H #include "os-proto.h" #endif #include "gencode.h" /* for "no_optimize" */ static int pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp); static int pcap_set_datalink_bpf(pcap_t *p, int dlt); static int pcap_stats_bpf(pcap_t *p, struct pcap_stat *ps) { struct bpf_stat s; /* * "ps_recv" counts packets handed to the filter, not packets * that passed the filter. This includes packets later dropped * because we ran out of buffer space. * * "ps_drop" counts packets dropped inside the BPF device * because we ran out of buffer space. It doesn't count * packets dropped by the interface driver. It counts * only packets that passed the filter. * * Both statistics include packets not yet read from the kernel * by libpcap, and thus not yet seen by the application. */ if (ioctl(p->fd, BIOCGSTATS, (caddr_t)&s) < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGSTATS: %s", pcap_strerror(errno)); return (-1); } ps->ps_recv = s.bs_recv; ps->ps_drop = s.bs_drop; return (0); } static int pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user) { int cc; int n = 0; register u_char *bp, *ep; struct bpf_insn *fcode; fcode = p->md.use_bpf ? NULL : p->fcode.bf_insns; again: /* * Has "pcap_breakloop()" been called? */ if (p->break_loop) { /* * Yes - clear the flag that indicates that it * has, and return -2 to indicate that we were * told to break out of the loop. */ p->break_loop = 0; return (-2); } cc = p->cc; if (p->cc == 0) { cc = read(p->fd, (char *)p->buffer, p->bufsize); if (cc < 0) { /* Don't choke when we get ptraced */ switch (errno) { case EINTR: goto again; #ifdef _AIX case EFAULT: /* * Sigh. More AIX wonderfulness. * * For some unknown reason the uiomove() * operation in the bpf kernel extension * used to copy the buffer into user * space sometimes returns EFAULT. I have * no idea why this is the case given that * a kernel debugger shows the user buffer * is correct. This problem appears to * be mostly mitigated by the memset of * the buffer before it is first used. * Very strange.... Shaun Clowes * * In any case this means that we shouldn't * treat EFAULT as a fatal error; as we * don't have an API for returning * a "some packets were dropped since * the last packet you saw" indication, * we just ignore EFAULT and keep reading. */ goto again; #endif case EWOULDBLOCK: return (0); #if defined(sun) && !defined(BSD) /* * Due to a SunOS bug, after 2^31 bytes, the kernel * file offset overflows and read fails with EINVAL. * The lseek() to 0 will fix things. */ case EINVAL: if (lseek(p->fd, 0L, SEEK_CUR) + p->bufsize < 0) { (void)lseek(p->fd, 0L, SEEK_SET); goto again; } /* fall through */ #endif } snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "read: %s", pcap_strerror(errno)); return (-1); } bp = p->buffer; } else bp = p->bp; /* * Loop through each packet. */ #define bhp ((struct bpf_hdr *)bp) ep = bp + cc; while (bp < ep) { register int caplen, hdrlen; /* * Has "pcap_breakloop()" been called? * If so, return immediately - if we haven't read any * packets, clear the flag and return -2 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) { if (n == 0) { p->break_loop = 0; return (-2); } else { p->bp = bp; p->cc = ep - bp; return (n); } } caplen = bhp->bh_caplen; hdrlen = bhp->bh_hdrlen; /* * Short-circuit evaluation: if using BPF filter * in kernel, no need to do it now. */ if (fcode == NULL || bpf_filter(fcode, bp + hdrlen, bhp->bh_datalen, caplen)) { #ifdef _AIX /* * AIX's BPF returns seconds/nanoseconds time * stamps, not seconds/microseconds time stamps. * * XXX - I'm guessing here that it's a "struct * timestamp"; if not, this code won't compile, * but, if not, you want to send us a bug report * and fall back on using DLPI. It's not as if * BPF used to work right on AIX before this * change; this change attempts to fix the fact * that it didn't.... */ bhp->bh_tstamp.tv_usec = bhp->bh_tstamp.tv_usec/1000; #endif /* * 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); } } else { /* * Skip this packet. */ bp += BPF_WORDALIGN(caplen + hdrlen); } } #undef bhp p->cc = 0; return (n); } #ifdef _AIX static int bpf_odminit(char *errbuf) { char *errstr; if (odm_initialize() == -1) { if (odm_err_msg(odmerrno, &errstr) == -1) errstr = "Unknown error"; snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: odm_initialize failed: %s", errstr); return (-1); } if ((odmlockid = odm_lock("/etc/objrepos/config_lock", ODM_WAIT)) == -1) { if (odm_err_msg(odmerrno, &errstr) == -1) errstr = "Unknown error"; snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: odm_lock of /etc/objrepos/config_lock failed: %s", errstr); return (-1); } return (0); } static int bpf_odmcleanup(char *errbuf) { char *errstr; if (odm_unlock(odmlockid) == -1) { if (odm_err_msg(odmerrno, &errstr) == -1) errstr = "Unknown error"; snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: odm_unlock failed: %s", errstr); return (-1); } if (odm_terminate() == -1) { if (odm_err_msg(odmerrno, &errstr) == -1) errstr = "Unknown error"; snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: odm_terminate failed: %s", errstr); return (-1); } return (0); } static int bpf_load(char *errbuf) { long major; int *minors; int numminors, i, rc; char buf[1024]; struct stat sbuf; struct bpf_config cfg_bpf; struct cfg_load cfg_ld; struct cfg_kmod cfg_km; /* * This is very very close to what happens in the real implementation * but I've fixed some (unlikely) bug situations. */ if (bpfloadedflag) return (0); if (bpf_odminit(errbuf) != 0) return (-1); major = genmajor(BPF_NAME); if (major == -1) { snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: genmajor failed: %s", pcap_strerror(errno)); return (-1); } minors = getminor(major, &numminors, BPF_NAME); if (!minors) { minors = genminor("bpf", major, 0, BPF_MINORS, 1, 1); if (!minors) { snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: genminor failed: %s", pcap_strerror(errno)); return (-1); } } if (bpf_odmcleanup(errbuf)) return (-1); rc = stat(BPF_NODE "0", &sbuf); if (rc == -1 && errno != ENOENT) { snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: can't stat %s: %s", BPF_NODE "0", pcap_strerror(errno)); return (-1); } if (rc == -1 || getmajor(sbuf.st_rdev) != major) { for (i = 0; i < BPF_MINORS; i++) { sprintf(buf, "%s%d", BPF_NODE, i); unlink(buf); if (mknod(buf, S_IRUSR | S_IFCHR, domakedev(major, i)) == -1) { snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: can't mknod %s: %s", buf, pcap_strerror(errno)); return (-1); } } } /* Check if the driver is loaded */ memset(&cfg_ld, 0x0, sizeof(cfg_ld)); cfg_ld.path = buf; sprintf(cfg_ld.path, "%s/%s", DRIVER_PATH, BPF_NAME); if ((sysconfig(SYS_QUERYLOAD, (void *)&cfg_ld, sizeof(cfg_ld)) == -1) || (cfg_ld.kmid == 0)) { /* Driver isn't loaded, load it now */ if (sysconfig(SYS_SINGLELOAD, (void *)&cfg_ld, sizeof(cfg_ld)) == -1) { snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: could not load driver: %s", strerror(errno)); return (-1); } } /* Configure the driver */ cfg_km.cmd = CFG_INIT; cfg_km.kmid = cfg_ld.kmid; cfg_km.mdilen = sizeof(cfg_bpf); cfg_km.mdiptr = (void *)&cfg_bpf; for (i = 0; i < BPF_MINORS; i++) { cfg_bpf.devno = domakedev(major, i); if (sysconfig(SYS_CFGKMOD, (void *)&cfg_km, sizeof(cfg_km)) == -1) { snprintf(errbuf, PCAP_ERRBUF_SIZE, "bpf_load: could not configure driver: %s", strerror(errno)); return (-1); } } bpfloadedflag = 1; return (0); } #endif static inline int bpf_open(pcap_t *p, char *errbuf) { int fd; int n = 0; char device[sizeof "/dev/bpf0000000000"]; #ifdef _AIX /* * Load the bpf driver, if it isn't already loaded, * and create the BPF device entries, if they don't * already exist. */ if (bpf_load(errbuf) == -1) return (-1); #endif /* * Go through all the minors and find one that isn't in use. */ do { (void)snprintf(device, sizeof(device), "/dev/bpf%d", n++); fd = open(device, O_RDONLY); } while (fd < 0 && errno == EBUSY); /* * XXX better message for all minors used */ if (fd < 0) snprintf(errbuf, PCAP_ERRBUF_SIZE, "(no devices found) %s: %s", device, pcap_strerror(errno)); return (fd); } static void pcap_close_bpf(pcap_t *p) { if (p->buffer != NULL) free(p->buffer); if (p->fd >= 0) close(p->fd); } /* * XXX - on AIX, IBM's tcpdump (and perhaps the incompatible-with-everybody- * else's libpcap in AIX 5.1) appears to forcibly load the BPF driver * if it's not already loaded, and to create the BPF devices if they * don't exist. * * It'd be nice if we could do the same, although the code to do so * might be version-dependent, alas (the way to do it isn't necessarily * documented). */ pcap_t * pcap_open_live(const char *device, int snaplen, int promisc, int to_ms, char *ebuf) { int fd; struct ifreq ifr; struct bpf_version bv; #ifdef BIOCGDLTLIST struct bpf_dltlist bdl; #endif u_int v; pcap_t *p; struct utsname osinfo; #ifdef HAVE_DAG_API if (strstr(device, "dag")) { return dag_open_live(device, snaplen, promisc, to_ms, ebuf); } #endif /* HAVE_DAG_API */ #ifdef BIOCGDLTLIST memset(&bdl, 0, sizeof(bdl)); #endif p = (pcap_t *)malloc(sizeof(*p)); if (p == NULL) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); return (NULL); } memset(p, 0, sizeof(*p)); fd = bpf_open(p, ebuf); if (fd < 0) goto bad; p->fd = fd; p->snapshot = snaplen; if (ioctl(fd, BIOCVERSION, (caddr_t)&bv) < 0) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCVERSION: %s", pcap_strerror(errno)); goto bad; } if (bv.bv_major != BPF_MAJOR_VERSION || bv.bv_minor < BPF_MINOR_VERSION) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "kernel bpf filter out of date"); goto bad; } /* * Try finding a good size for the buffer; 32768 may be too * big, so keep cutting it in half until we find a size * that works, or run out of sizes to try. If the default * is larger, don't make it smaller. * * XXX - there should be a user-accessible hook to set the * initial buffer size. */ if ((ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) || v < 32768) v = 32768; for ( ; v != 0; v >>= 1) { /* 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); (void)strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name)); if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) >= 0) break; /* that size worked; we're done */ if (errno != ENOBUFS) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSETIF: %s: %s", device, pcap_strerror(errno)); goto bad; } } if (v == 0) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSBLEN: %s: No buffer size worked", device); goto bad; } /* Get the data link layer type. */ if (ioctl(fd, BIOCGDLT, (caddr_t)&v) < 0) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLT: %s", pcap_strerror(errno)); goto bad; } #ifdef _AIX /* * AIX's BPF returns IFF_ types, not DLT_ types, in BIOCGDLT. */ switch (v) { case IFT_ETHER: case IFT_ISO88023: v = DLT_EN10MB; break; case IFT_FDDI: v = DLT_FDDI; break; case IFT_ISO88025: v = DLT_IEEE802; break; case IFT_LOOP: v = DLT_NULL; break; default: /* * We don't know what to map this to yet. */ snprintf(ebuf, PCAP_ERRBUF_SIZE, "unknown interface type %u", v); goto bad; } #endif #if _BSDI_VERSION - 0 >= 199510 /* The SLIP and PPP link layer header changed in BSD/OS 2.1 */ switch (v) { case DLT_SLIP: v = DLT_SLIP_BSDOS; break; case DLT_PPP: v = DLT_PPP_BSDOS; break; case 11: /*DLT_FR*/ v = DLT_FRELAY; break; case 12: /*DLT_C_HDLC*/ v = DLT_CHDLC; break; } #endif p->linktype = v; #ifdef BIOCGDLTLIST /* * 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 (ioctl(fd, BIOCGDLTLIST, (caddr_t)&bdl) == 0) { bdl.bfl_list = (u_int *) malloc(sizeof(u_int) * bdl.bfl_len); if (bdl.bfl_list == NULL) { (void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); goto bad; } if (ioctl(fd, BIOCGDLTLIST, (caddr_t)&bdl) < 0) { (void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLTLIST: %s", pcap_strerror(errno)); goto bad; } p->dlt_count = bdl.bfl_len; p->dlt_list = bdl.bfl_list; } else { if (errno != EINVAL) { (void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLTLIST: %s", pcap_strerror(errno)); goto bad; } } #endif /* set timeout */ if (to_ms != 0) { /* * XXX - is this seconds/nanoseconds in AIX? * (Treating it as such doesn't fix the timeout * problem described below.) */ struct timeval to; to.tv_sec = to_ms / 1000; to.tv_usec = (to_ms * 1000) % 1000000; if (ioctl(p->fd, BIOCSRTIMEOUT, (caddr_t)&to) < 0) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT: %s", pcap_strerror(errno)); goto bad; } } #ifdef _AIX #ifdef BIOCIMMEDIATE /* * Darren Reed notes that * * On AIX (4.2 at least), if BIOCIMMEDIATE is not set, the * timeout appears to be ignored and it waits until the buffer * is filled before returning. The result of not having it * set is almost worse than useless if your BPF filter * is reducing things to only a few packets (i.e. one every * second or so). * * so we turn BIOCIMMEDIATE mode on if this is AIX. * * We don't turn it on for other platforms, as that means we * get woken up for every packet, which may not be what we want; * in the Winter 1993 USENIX paper on BPF, they say: * * Since a process might want to look at every packet on a * network and the time between packets can be only a few * microseconds, it is not possible to do a read system call * per packet and BPF must collect the data from several * packets and return it as a unit when the monitoring * application does a read. * * which I infer is the reason for the timeout - it means we * wait that amount of time, in the hopes that more packets * will arrive and we'll get them all with one read. * * Setting BIOCIMMEDIATE mode on FreeBSD (and probably other * BSDs) causes the timeout to be ignored. * * On the other hand, some platforms (e.g., Linux) don't support * timeouts, they just hand stuff to you as soon as it arrives; * if that doesn't cause a problem on those platforms, it may * be OK to have BIOCIMMEDIATE mode on BSD as well. * * (Note, though, that applications may depend on the read * completing, even if no packets have arrived, when the timeout * expires, e.g. GUI applications that have to check for input * while waiting for packets to arrive; a non-zero timeout * prevents "select()" from working right on FreeBSD and * possibly other BSDs, as the timer doesn't start until a * "read()" is done, so the timer isn't in effect if the * application is blocked on a "select()", and the "select()" * doesn't get woken up for a BPF device until the buffer * fills up.) */ v = 1; if (ioctl(p->fd, BIOCIMMEDIATE, &v) < 0) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCIMMEDIATE: %s", pcap_strerror(errno)); goto bad; } #endif /* BIOCIMMEDIATE */ #endif /* _AIX */ if (promisc) { /* set promiscuous mode, okay if it fails */ if (ioctl(p->fd, BIOCPROMISC, NULL) < 0) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCPROMISC: %s", pcap_strerror(errno)); } } if (ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGBLEN: %s", pcap_strerror(errno)); goto bad; } p->bufsize = v; p->buffer = (u_char *)malloc(p->bufsize); if (p->buffer == NULL) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); goto bad; } #ifdef _AIX /* For some strange reason this seems to prevent the EFAULT * problems we have experienced from AIX BPF. */ memset(p->buffer, 0x0, p->bufsize); #endif /* * On most BPF platforms, either you can do a "select()" or * "poll()" on a BPF file descriptor and it works correctly, * or you can do it and it will return "readable" if the * hold buffer is full but not if the timeout expires *and* * a non-blocking read will, if the hold buffer is empty * but the store buffer isn't empty, rotate the buffers * and return what packets are available. * * In the latter case, the fact that a non-blocking read * will give you the available packets means you can work * around the failure of "select()" and "poll()" to wake up * and return "readable" when the timeout expires by using * the timeout as the "select()" or "poll()" timeout, putting * the BPF descriptor into non-blocking mode, and read from * it regardless of whether "select()" reports it as readable * or not. * * However, in FreeBSD 4.3 and 4.4, "select()" and "poll()" * won't wake up and return "readable" if the timer expires * and non-blocking reads return EWOULDBLOCK if the hold * buffer is empty, even if the store buffer is non-empty. * * This means the workaround in question won't work. * * Therefore, on FreeBSD 4.3 and 4.4, we set "p->selectable_fd" * to -1, which means "sorry, you can't use 'select()' or 'poll()' * here". On all other BPF platforms, we set it to the FD for * the BPF device; in NetBSD, OpenBSD, and Darwin, a non-blocking * read will, if the hold buffer is empty and the store buffer * isn't empty, rotate the buffers and return what packets are * there (and in sufficiently recent versions of OpenBSD * "select()" and "poll()" should work correctly). * * XXX - what about AIX? */ if (uname(&osinfo) == 0) { /* * We can check what OS this is. */ if (strcmp(osinfo.sysname, "FreeBSD") == 0 && (strcmp(osinfo.release, "4.3") == 0 || strcmp(osinfo.release, "4.4") == 0)) p->selectable_fd = -1; else p->selectable_fd = p->fd; } else { /* * We can't find out what OS this is, so assume we can * do a "select()" or "poll()". */ p->selectable_fd = p->fd; } p->read_op = pcap_read_bpf; p->setfilter_op = pcap_setfilter_bpf; p->set_datalink_op = pcap_set_datalink_bpf; p->getnonblock_op = pcap_getnonblock_fd; p->setnonblock_op = pcap_setnonblock_fd; p->stats_op = pcap_stats_bpf; p->close_op = pcap_close_bpf; return (p); bad: (void)close(fd); #ifdef BIOCGDLTLIST if (bdl.bfl_list != NULL) free(bdl.bfl_list); #endif free(p); return (NULL); } int pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf) { #ifdef HAVE_DAG_API if (dag_platform_finddevs(alldevsp, errbuf) < 0) return (-1); #endif /* HAVE_DAG_API */ return (0); } static int pcap_setfilter_bpf(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) { /* * XXX - what if we already have a filter in the kernel? */ if (install_bpf_program(p, fp) < 0) return (-1); p->md.use_bpf = 0; /* filtering in userland */ return (0); } /* * Free any user-mode filter we might happen to have installed. */ pcap_freecode(&p->fcode); /* * Try to install the kernel filter. */ if (ioctl(p->fd, BIOCSETF, (caddr_t)fp) < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETF: %s", pcap_strerror(errno)); return (-1); } p->md.use_bpf = 1; /* filtering in the kernel */ return (0); } static int pcap_set_datalink_bpf(pcap_t *p, int dlt) { #ifdef BIOCSDLT if (ioctl(p->fd, BIOCSDLT, &dlt) == -1) { (void) snprintf(p->errbuf, sizeof(p->errbuf), "Cannot set DLT %d: %s", dlt, strerror(errno)); return (-1); } #endif return (0); }