/* * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996 * 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. * * packet filter subroutines for tcpdump * Extraction/creation by Jeffrey Mogul, DECWRL */ #ifndef lint static const char rcsid[] _U_ = "@(#) $Header: /tcpdump/master/libpcap/pcap-pf.c,v 1.94.2.3 2008-04-14 20:41:52 guy Exp $ (LBL)"; #endif #ifdef HAVE_CONFIG_H #include "config.h" #endif #include #include #include #include #include #include #include struct mbuf; struct rtentry; #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Make "pcap.h" not include "pcap/bpf.h"; we are going to include the * native OS version, as we need various BPF ioctls from it. */ #define PCAP_DONT_INCLUDE_PCAP_BPF_H #include #include "pcap-int.h" #ifdef HAVE_OS_PROTO_H #include "os-proto.h" #endif static int pcap_setfilter_pf(pcap_t *, struct bpf_program *); /* * BUFSPACE is the size in bytes of the packet read buffer. Most tcpdump * applications aren't going to need more than 200 bytes of packet header * and the read shouldn't return more packets than packetfilter's internal * queue limit (bounded at 256). */ #define BUFSPACE (200 * 256) static int pcap_read_pf(pcap_t *pc, int cnt, pcap_handler callback, u_char *user) { register u_char *p, *bp; register int cc, n, buflen, inc; register struct enstamp *sp; #ifdef LBL_ALIGN struct enstamp stamp; #endif #ifdef PCAP_FDDIPAD register int pad; #endif again: cc = pc->cc; if (cc == 0) { cc = read(pc->fd, (char *)pc->buffer + pc->offset, pc->bufsize); if (cc < 0) { if (errno == EWOULDBLOCK) return (0); if (errno == EINVAL && lseek(pc->fd, 0L, SEEK_CUR) + pc->bufsize < 0) { /* * Due to a kernel bug, after 2^31 bytes, * the kernel file offset overflows and * read fails with EINVAL. The lseek() * to 0 will fix things. */ (void)lseek(pc->fd, 0L, SEEK_SET); goto again; } snprintf(pc->errbuf, sizeof(pc->errbuf), "pf read: %s", pcap_strerror(errno)); return (-1); } bp = pc->buffer + pc->offset; } else bp = pc->bp; /* * Loop through each packet. */ n = 0; #ifdef PCAP_FDDIPAD pad = pc->fddipad; #endif while (cc > 0) { /* * 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 (pc->break_loop) { if (n == 0) { pc->break_loop = 0; return (-2); } else { pc->cc = cc; pc->bp = bp; return (n); } } if (cc < sizeof(*sp)) { snprintf(pc->errbuf, sizeof(pc->errbuf), "pf short read (%d)", cc); return (-1); } #ifdef LBL_ALIGN if ((long)bp & 3) { sp = &stamp; memcpy((char *)sp, (char *)bp, sizeof(*sp)); } else #endif sp = (struct enstamp *)bp; if (sp->ens_stamplen != sizeof(*sp)) { snprintf(pc->errbuf, sizeof(pc->errbuf), "pf short stamplen (%d)", sp->ens_stamplen); return (-1); } p = bp + sp->ens_stamplen; buflen = sp->ens_count; if (buflen > pc->snapshot) buflen = pc->snapshot; /* Calculate inc before possible pad update */ inc = ENALIGN(buflen + sp->ens_stamplen); cc -= inc; bp += inc; pc->md.TotPkts++; pc->md.TotDrops += sp->ens_dropped; pc->md.TotMissed = sp->ens_ifoverflows; if (pc->md.OrigMissed < 0) pc->md.OrigMissed = pc->md.TotMissed; /* * Short-circuit evaluation: if using BPF filter * in kernel, no need to do it now - we already know * the packet passed the filter. * #ifdef PCAP_FDDIPAD * Note: the filter code was generated assuming * that pc->fddipad was the amount of padding * before the header, as that's what's required * in the kernel, so we run the filter before * skipping that padding. #endif */ if (pc->md.use_bpf || bpf_filter(pc->fcode.bf_insns, p, sp->ens_count, buflen)) { struct pcap_pkthdr h; pc->md.TotAccepted++; h.ts = sp->ens_tstamp; #ifdef PCAP_FDDIPAD h.len = sp->ens_count - pad; #else h.len = sp->ens_count; #endif #ifdef PCAP_FDDIPAD p += pad; buflen -= pad; #endif h.caplen = buflen; (*callback)(user, &h, p); if (++n >= cnt && cnt > 0) { pc->cc = cc; pc->bp = bp; return (n); } } } pc->cc = 0; return (n); } static int pcap_inject_pf(pcap_t *p, const void *buf, size_t size) { int ret; ret = write(p->fd, buf, size); if (ret == -1) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "send: %s", pcap_strerror(errno)); return (-1); } return (ret); } static int pcap_stats_pf(pcap_t *p, struct pcap_stat *ps) { /* * If packet filtering is being done in the kernel: * * "ps_recv" counts only packets that passed the filter. * This does not include packets dropped because we * ran out of buffer space. (XXX - perhaps it should, * by adding "ps_drop" to "ps_recv", for compatibility * with some other platforms. On the other hand, on * some platforms "ps_recv" counts only packets that * passed the filter, and on others it counts packets * that didn't pass the filter....) * * "ps_drop" counts packets that passed the kernel filter * (if any) but were dropped because the input queue was * full. * * "ps_ifdrop" counts packets dropped by the network * inteface (regardless of whether they would have passed * the input filter, of course). * * If packet filtering is not being done in the kernel: * * "ps_recv" counts only packets that passed the filter. * * "ps_drop" counts packets that were dropped because the * input queue was full, regardless of whether they passed * the userland filter. * * "ps_ifdrop" counts packets dropped by the network * inteface (regardless of whether they would have passed * the input filter, of course). * * These statistics don't include packets not yet read from * the kernel by libpcap, but they may include packets not * yet read from libpcap by the application. */ ps->ps_recv = p->md.TotAccepted; ps->ps_drop = p->md.TotDrops; ps->ps_ifdrop = p->md.TotMissed - p->md.OrigMissed; return (0); } /* * We include the OS's , not our "pcap/bpf.h", so we probably * don't get DLT_DOCSIS defined. */ #ifndef DLT_DOCSIS #define DLT_DOCSIS 143 #endif static int pcap_activate_pf(pcap_t *p) { short enmode; int backlog = -1; /* request the most */ struct enfilter Filter; struct endevp devparams; /* * Initially try a read/write open (to allow the inject * method to work). If that fails due to permission * issues, fall back to read-only. This allows a * non-root user to be granted specific access to pcap * capabilities via file permissions. * * XXX - we should have an API that has a flag that * controls whether to open read-only or read-write, * so that denial of permission to send (or inability * to send, if sending packets isn't supported on * the device in question) can be indicated at open * time. * * XXX - we assume here that "pfopen()" does not, in fact, modify * its argument, even though it takes a "char *" rather than a * "const char *" as its first argument. That appears to be * the case, at least on Digital UNIX 4.0. */ p->fd = pfopen(p->opt.source, O_RDWR); if (p->fd == -1 && errno == EACCES) p->fd = pfopen(p->opt.source, O_RDONLY); if (p->fd < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "pf open: %s: %s\n\ your system may not be properly configured; see the packetfilter(4) man page\n", p->opt.source, pcap_strerror(errno)); goto bad; } p->md.OrigMissed = -1; enmode = ENTSTAMP|ENBATCH|ENNONEXCL; if (p->opt.promisc) enmode |= ENPROMISC; if (ioctl(p->fd, EIOCMBIS, (caddr_t)&enmode) < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCMBIS: %s", pcap_strerror(errno)); goto bad; } #ifdef ENCOPYALL /* Try to set COPYALL mode so that we see packets to ourself */ enmode = ENCOPYALL; (void)ioctl(p->fd, EIOCMBIS, (caddr_t)&enmode);/* OK if this fails */ #endif /* set the backlog */ if (ioctl(p->fd, EIOCSETW, (caddr_t)&backlog) < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCSETW: %s", pcap_strerror(errno)); goto bad; } /* discover interface type */ if (ioctl(p->fd, EIOCDEVP, (caddr_t)&devparams) < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCDEVP: %s", pcap_strerror(errno)); goto bad; } /* HACK: to compile prior to Ultrix 4.2 */ #ifndef ENDT_FDDI #define ENDT_FDDI 4 #endif switch (devparams.end_dev_type) { case ENDT_10MB: p->linktype = DLT_EN10MB; p->offset = 2; /* * This is (presumably) a real Ethernet capture; give it a * link-layer-type list with DLT_EN10MB and DLT_DOCSIS, so * that an application can let you choose it, in case you're * capturing DOCSIS traffic that a Cisco Cable Modem * Termination System is putting out onto an Ethernet (it * doesn't put an Ethernet header onto the wire, it puts raw * DOCSIS frames out on the wire inside the low-level * Ethernet framing). */ p->dlt_list = (u_int *) malloc(sizeof(u_int) * 2); /* * If that fails, just leave the list empty. */ if (p->dlt_list != NULL) { p->dlt_list[0] = DLT_EN10MB; p->dlt_list[1] = DLT_DOCSIS; p->dlt_count = 2; } break; case ENDT_FDDI: p->linktype = DLT_FDDI; break; #ifdef ENDT_SLIP case ENDT_SLIP: p->linktype = DLT_SLIP; break; #endif #ifdef ENDT_PPP case ENDT_PPP: p->linktype = DLT_PPP; break; #endif #ifdef ENDT_LOOPBACK case ENDT_LOOPBACK: /* * It appears to use Ethernet framing, at least on * Digital UNIX 4.0. */ p->linktype = DLT_EN10MB; p->offset = 2; break; #endif #ifdef ENDT_TRN case ENDT_TRN: p->linktype = DLT_IEEE802; break; #endif default: /* * XXX - what about ENDT_IEEE802? The pfilt.h header * file calls this "IEEE 802 networks (non-Ethernet)", * but that doesn't specify a specific link layer type; * it could be 802.4, or 802.5 (except that 802.5 is * ENDT_TRN), or 802.6, or 802.11, or.... That's why * DLT_IEEE802 was hijacked to mean Token Ring in various * BSDs, and why we went along with that hijacking. * * XXX - what about ENDT_HDLC and ENDT_NULL? * Presumably, as ENDT_OTHER is just "Miscellaneous * framing", there's not much we can do, as that * doesn't specify a particular type of header. */ snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "unknown data-link type %u", devparams.end_dev_type); goto bad; } /* set truncation */ #ifdef PCAP_FDDIPAD if (p->linktype == DLT_FDDI) { p->fddipad = PCAP_FDDIPAD; /* packetfilter includes the padding in the snapshot */ p->snapshot += PCAP_FDDIPAD; } else p->fddipad = 0; #endif if (ioctl(p->fd, EIOCTRUNCATE, (caddr_t)&p->snapshot) < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCTRUNCATE: %s", pcap_strerror(errno)); goto bad; } /* accept all packets */ memset(&Filter, 0, sizeof(Filter)); Filter.enf_Priority = 37; /* anything > 2 */ Filter.enf_FilterLen = 0; /* means "always true" */ if (ioctl(p->fd, EIOCSETF, (caddr_t)&Filter) < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCSETF: %s", pcap_strerror(errno)); goto bad; } if (p->md.timeout != 0) { struct timeval timeout; timeout.tv_sec = p->md.timeout / 1000; timeout.tv_usec = (p->md.timeout * 1000) % 1000000; if (ioctl(p->fd, EIOCSRTIMEOUT, (caddr_t)&timeout) < 0) { snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCSRTIMEOUT: %s", pcap_strerror(errno)); goto bad; } } p->bufsize = BUFSPACE; p->buffer = (u_char*)malloc(p->bufsize + p->offset); if (p->buffer == NULL) { strlcpy(p->errbuf, pcap_strerror(errno), PCAP_ERRBUF_SIZE); goto bad; } /* * "select()" and "poll()" work on packetfilter devices. */ p->selectable_fd = p->fd; p->read_op = pcap_read_pf; p->inject_op = pcap_inject_pf; p->setfilter_op = pcap_setfilter_pf; p->setdirection_op = NULL; /* Not implemented. */ p->set_datalink_op = NULL; /* can't change data link type */ p->getnonblock_op = pcap_getnonblock_fd; p->setnonblock_op = pcap_setnonblock_fd; p->stats_op = pcap_stats_pf; return (0); bad: return (PCAP_ERROR); } pcap_t * pcap_create(const char *device, char *ebuf) { pcap_t *p; p = pcap_create_common(device, ebuf); if (p == NULL) return (NULL); p->activate_op = pcap_activate_pf; return (p); } int pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf) { return (0); } static int pcap_setfilter_pf(pcap_t *p, struct bpf_program *fp) { struct bpf_version bv; /* * See if BIOCVERSION works. If not, we assume the kernel doesn't * support BPF-style filters (it's not documented in the bpf(7) * or packetfiler(7) man pages, but the code used to fail if * BIOCSETF worked but BIOCVERSION didn't, and I've seen it do * kernel filtering in DU 4.0, so presumably BIOCVERSION works * there, at least). */ if (ioctl(p->fd, BIOCVERSION, (caddr_t)&bv) >= 0) { /* * OK, we have the version of the BPF interpreter; * is it the same major version as us, and the same * or better minor version? */ if (bv.bv_major == BPF_MAJOR_VERSION && bv.bv_minor >= BPF_MINOR_VERSION) { /* * Yes. Try to install the filter. */ if (ioctl(p->fd, BIOCSETF, (caddr_t)fp) < 0) { snprintf(p->errbuf, sizeof(p->errbuf), "BIOCSETF: %s", pcap_strerror(errno)); return (-1); } /* * OK, that succeeded. We're doing filtering in * the kernel. (We assume we don't have a * userland filter installed - that'd require * a previous version check to have failed but * this one to succeed.) * * XXX - this message should be supplied to the * application as a warning of some sort, * except that if it's a GUI application, it's * not clear that it should be displayed in * a window to annoy the user. */ fprintf(stderr, "tcpdump: Using kernel BPF filter\n"); p->md.use_bpf = 1; /* * Discard any previously-received packets, * as they might have passed whatever filter * was formerly in effect, but might not pass * this filter (BIOCSETF discards packets buffered * in the kernel, so you can lose packets in any * case). */ p->cc = 0; return (0); } /* * We can't use the kernel's BPF interpreter; don't give * up, just log a message and be inefficient. * * XXX - this should really be supplied to the application * as a warning of some sort. */ fprintf(stderr, "tcpdump: Requires BPF language %d.%d or higher; kernel is %d.%d\n", BPF_MAJOR_VERSION, BPF_MINOR_VERSION, bv.bv_major, bv.bv_minor); } /* * We couldn't do filtering in the kernel; do it in userland. */ if (install_bpf_program(p, fp) < 0) return (-1); /* * XXX - this message should be supplied by the application as * a warning of some sort. */ fprintf(stderr, "tcpdump: Filtering in user process\n"); p->md.use_bpf = 0; return (0); }