pcap-linux.c

Ubuntu packages of security software。 相当不错的源码

	 */
	stats->ps_recv = handle->md.packets_read;
	stats->ps_drop = 0;
	return 0;
}

/*
 * Description string for the "any" device.
 */
static const char any_descr[] = "Pseudo-device that captures on all interfaces";

int
pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
{
	if (pcap_add_if(alldevsp, "any", 0, any_descr, errbuf) < 0)
		return (-1);

#ifdef HAVE_DAG_API
	if (dag_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif /* HAVE_DAG_API */

#ifdef HAVE_SEPTEL_API
	if (septel_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif /* HAVE_SEPTEL_API */

	return (0);
}

/*
 *  Attach the given BPF code to the packet capture device.
 */
static int
pcap_setfilter_linux(pcap_t *handle, struct bpf_program *filter)
{
#ifdef SO_ATTACH_FILTER
	struct sock_fprog	fcode;
	int			can_filter_in_kernel;
	int			err = 0;
#endif

	if (!handle)
		return -1;
	if (!filter) {
	        strncpy(handle->errbuf, "setfilter: No filter specified",
			sizeof(handle->errbuf));
		return -1;
	}

	/* Make our private copy of the filter */

	if (install_bpf_program(handle, filter) < 0)
		/* install_bpf_program() filled in errbuf */
		return -1;

	/*
	 * Run user level packet filter by default. Will be overriden if
	 * installing a kernel filter succeeds.
	 */
	handle->md.use_bpf = 0;

	/* Install kernel level filter if possible */

#ifdef SO_ATTACH_FILTER
#ifdef USHRT_MAX
	if (handle->fcode.bf_len > USHRT_MAX) {
		/*
		 * fcode.len is an unsigned short for current kernel.
		 * I have yet to see BPF-Code with that much
		 * instructions but still it is possible. So for the
		 * sake of correctness I added this check.
		 */
		fprintf(stderr, "Warning: Filter too complex for kernel\n");
		fcode.len = 0;
		fcode.filter = NULL;
		can_filter_in_kernel = 0;
	} else
#endif /* USHRT_MAX */
	{
		/*
		 * Oh joy, the Linux kernel uses struct sock_fprog instead
		 * of struct bpf_program and of course the length field is
		 * of different size. Pointed out by Sebastian
		 *
		 * Oh, and we also need to fix it up so that all "ret"
		 * instructions with non-zero operands have 65535 as the
		 * operand, and so that, if we're in cooked mode, all
		 * memory-reference instructions use special magic offsets
		 * in references to the link-layer header and assume that
		 * the link-layer payload begins at 0; "fix_program()"
		 * will do that.
		 */
		switch (fix_program(handle, &fcode)) {

		case -1:
		default:
			/*
			 * Fatal error; just quit.
			 * (The "default" case shouldn't happen; we
			 * return -1 for that reason.)
			 */
			return -1;

		case 0:
			/*
			 * The program performed checks that we can't make
			 * work in the kernel.
			 */
			can_filter_in_kernel = 0;
			break;

		case 1:
			/*
			 * We have a filter that'll work in the kernel.
			 */
			can_filter_in_kernel = 1;
			break;
		}
	}

	if (can_filter_in_kernel) {
		if ((err = set_kernel_filter(handle, &fcode)) == 0)
		{
			/* Installation succeded - using kernel filter. */
			handle->md.use_bpf = 1;
		}
		else if (err == -1)	/* Non-fatal error */
		{
			/*
			 * Print a warning if we weren't able to install
			 * the filter for a reason other than "this kernel
			 * isn't configured to support socket filters.
			 */
			if (errno != ENOPROTOOPT && errno != EOPNOTSUPP) {
				fprintf(stderr,
				    "Warning: Kernel filter failed: %s\n",
					pcap_strerror(errno));
			}
		}
	}

	/*
	 * If we're not using the kernel filter, get rid of any kernel
	 * filter that might've been there before, e.g. because the
	 * previous filter could work in the kernel, or because some other
	 * code attached a filter to the socket by some means other than
	 * calling "pcap_setfilter()".  Otherwise, the kernel filter may
	 * filter out packets that would pass the new userland filter.
	 */
	if (!handle->md.use_bpf)
		reset_kernel_filter(handle);

	/*
	 * Free up the copy of the filter that was made by "fix_program()".
	 */
	if (fcode.filter != NULL)
		free(fcode.filter);

	if (err == -2)
		/* Fatal error */
		return -1;
#endif /* SO_ATTACH_FILTER */

	return 0;
}

/*
 * Set direction flag: Which packets do we accept on a forwarding
 * single device? IN, OUT or both?
 */
static int
pcap_setdirection_linux(pcap_t *handle, pcap_direction_t d)
{
#ifdef HAVE_PF_PACKET_SOCKETS
	if (!handle->md.sock_packet) {
		handle->direction = d;
		return 0;
	}
#endif
	/*
	 * We're not using PF_PACKET sockets, so we can't determine
	 * the direction of the packet.
	 */
	snprintf(handle->errbuf, sizeof(handle->errbuf),
	    "Setting direction is not supported on SOCK_PACKET sockets");
	return -1;
}

/*
 *  Linux uses the ARP hardware type to identify the type of an
 *  interface. pcap uses the DLT_xxx constants for this. This
 *  function takes a pointer to a "pcap_t", and an ARPHRD_xxx
 *  constant, as arguments, and sets "handle->linktype" to the
 *  appropriate DLT_XXX constant and sets "handle->offset" to
 *  the appropriate value (to make "handle->offset" plus link-layer
 *  header length be a multiple of 4, so that the link-layer payload
 *  will be aligned on a 4-byte boundary when capturing packets).
 *  (If the offset isn't set here, it'll be 0; add code as appropriate
 *  for cases where it shouldn't be 0.)
 *
 *  If "cooked_ok" is non-zero, we can use DLT_LINUX_SLL and capture
 *  in cooked mode; otherwise, we can't use cooked mode, so we have
 *  to pick some type that works in raw mode, or fail.
 *
 *  Sets the link type to -1 if unable to map the type.
 */
static void map_arphrd_to_dlt(pcap_t *handle, int arptype, int cooked_ok)
{
	switch (arptype) {

	case ARPHRD_ETHER:
		/*
		 * 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).
		 *
		 * XXX - are there any sorts of "fake Ethernet" that have
		 * ARPHRD_ETHER but that *shouldn't offer DLT_DOCSIS as
		 * a Cisco CMTS won't put traffic onto it or get traffic
		 * bridged onto it?  ISDN is handled in "live_open_new()",
		 * as we fall back on cooked mode there; are there any
		 * others?
		 */
		handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
		/*
		 * If that fails, just leave the list empty.
		 */
		if (handle->dlt_list != NULL) {
			handle->dlt_list[0] = DLT_EN10MB;
			handle->dlt_list[1] = DLT_DOCSIS;
			handle->dlt_count = 2;
		}
		/* FALLTHROUGH */

	case ARPHRD_METRICOM:
	case ARPHRD_LOOPBACK:
		handle->linktype = DLT_EN10MB;
		handle->offset = 2;
		break;

	case ARPHRD_EETHER:
		handle->linktype = DLT_EN3MB;
		break;

	case ARPHRD_AX25:
		handle->linktype = DLT_AX25;
		break;

	case ARPHRD_PRONET:
		handle->linktype = DLT_PRONET;
		break;

	case ARPHRD_CHAOS:
		handle->linktype = DLT_CHAOS;
		break;

#ifndef ARPHRD_IEEE802_TR
#define ARPHRD_IEEE802_TR 800	/* From Linux 2.4 */
#endif
	case ARPHRD_IEEE802_TR:
	case ARPHRD_IEEE802:
		handle->linktype = DLT_IEEE802;
		handle->offset = 2;
		break;

	case ARPHRD_ARCNET:
		handle->linktype = DLT_ARCNET_LINUX;
		break;

#ifndef ARPHRD_FDDI	/* From Linux 2.2.13 */
#define ARPHRD_FDDI	774
#endif
	case ARPHRD_FDDI:
		handle->linktype = DLT_FDDI;
		handle->offset = 3;
		break;

#ifndef ARPHRD_ATM  /* FIXME: How to #include this? */
#define ARPHRD_ATM 19
#endif
	case ARPHRD_ATM:
		/*
		 * The Classical IP implementation in ATM for Linux
		 * supports both what RFC 1483 calls "LLC Encapsulation",
		 * in which each packet has an LLC header, possibly
		 * with a SNAP header as well, prepended to it, and
		 * what RFC 1483 calls "VC Based Multiplexing", in which
		 * different virtual circuits carry different network
		 * layer protocols, and no header is prepended to packets.
		 *
		 * They both have an ARPHRD_ type of ARPHRD_ATM, so
		 * you can't use the ARPHRD_ type to find out whether
		 * captured packets will have an LLC header, and,
		 * while there's a socket ioctl to *set* the encapsulation
		 * type, there's no ioctl to *get* the encapsulation type.
		 *
		 * This means that
		 *
		 *	programs that dissect Linux Classical IP frames
		 *	would have to check for an LLC header and,
		 *	depending on whether they see one or not, dissect
		 *	the frame as LLC-encapsulated or as raw IP (I
		 *	don't know whether there's any traffic other than
		 *	IP that would show up on the socket, or whether
		 *	there's any support for IPv6 in the Linux
		 *	Classical IP code);
		 *
		 *	filter expressions would have to compile into
		 *	code that checks for an LLC header and does
		 *	the right thing.
		 *
		 * Both of those are a nuisance - and, at least on systems
		 * that support PF_PACKET sockets, we don't have to put
		 * up with those nuisances; instead, we can just capture
		 * in cooked mode.  That's what we'll do, if we can.
		 * Otherwise, we'll just fail.
		 */
		if (cooked_ok)
			handle->linktype = DLT_LINUX_SLL;
		else
			handle->linktype = -1;
		break;

#ifndef ARPHRD_IEEE80211  /* From Linux 2.4.6 */
#define ARPHRD_IEEE80211 801
#endif
	case ARPHRD_IEEE80211:
		handle->linktype = DLT_IEEE802_11;
		break;

#ifndef ARPHRD_IEEE80211_PRISM  /* From Linux 2.4.18 */
#define ARPHRD_IEEE80211_PRISM 802
#endif
	case ARPHRD_IEEE80211_PRISM:
		handle->linktype = DLT_PRISM_HEADER;
		break;

#ifndef ARPHRD_IEEE80211_RADIOTAP /* new */
#define ARPHRD_IEEE80211_RADIOTAP 803
#endif
	case ARPHRD_IEEE80211_RADIOTAP:
		handle->linktype = DLT_IEEE802_11_RADIO;
		break;

	case ARPHRD_PPP:
		/*
		 * Some PPP code in the kernel supplies no link-layer
		 * header whatsoever to PF_PACKET sockets; other PPP
		 * code supplies PPP link-layer headers ("syncppp.c");
		 * some PPP code might supply random link-layer
		 * headers (PPP over ISDN - there's code in Ethereal,
		 * for example, to cope with PPP-over-ISDN captures
		 * with which the Ethereal developers have had to cope,
		 * heuristically trying to determine which of the
		 * oddball link-layer headers particular packets have).
		 *
		 * As such, we just punt, and run all PPP interfaces
		 * in cooked mode, if we can; otherwise, we just treat
		 * it as DLT_RAW, for now - if somebody needs to capture,
		 * on a 2.0[.x] kernel, on PPP devices that supply a
		 * link-layer header, they'll have to add code here to
		 * map to the appropriate DLT_ type (possibly adding a
		 * new DLT_ type, if necessary).
		 */
		if (cooked_ok)
			handle->linktype = DLT_LINUX_SLL;
		else {
			/*
			 * XXX - handle ISDN types here?  We can't fall
			 * back on cooked sockets, so we'd have to
			 * figure out from the device name what type of
			 * link-layer encapsulation it's using, and map
			 * that to an appropriate DLT_ value, meaning
			 * we'd map "isdnN" devices to DLT_RAW (they
			 * supply raw IP packets with no link-layer
			 * header) and "isdY" devices to a new DLT_I4L_IP
			 * type that has only an Ethernet packet type as
			 * a link-layer header.
			 *
			 * But sometimes we seem to get random crap
			 * in the link-layer header when capturing on
			 * ISDN devices....
			 */
			handle->linktype = DLT_RAW;
		}
		break;

#ifndef ARPHRD_CISCO
#define ARPHRD_CISCO 513 /* previously ARPHRD_HDLC */
#endif
	case ARPHRD_CISCO:
		handle->linktype = DLT_C_HDLC;
		break;

	/* Not sure if this is correct for all tunnels, but it
	 * works for CIPE */
	case ARPHRD_TUNNEL:
#ifndef ARPHRD_SIT
#define ARPHRD_SIT 776	/* From Linux 2.2.13 */
#endif
	case ARPHRD_SIT:
	case ARPHRD_CSLIP:
	case ARPHRD_SLIP6:
	case ARPHRD_CSLIP6:
	case ARPHRD_ADAPT:
	case ARPHRD_SLIP:
#ifndef ARPHRD_RAWHDLC
#define ARPHRD_RAWHDLC 518
#endif
	case ARPHRD_RAWHDLC:
#ifndef ARPHRD_DLCI
#define ARPHRD_DLCI 15
#endif
	case ARPHRD_DLCI:
		/*
		 * XXX - should some of those be mapped to DLT_LINUX_SLL
		 * instead?  Should we just map all of them to DLT_LINUX_SLL?
		 */
		handle->linktype = DLT_RAW;
		break;

#ifndef ARPHRD_FRAD
#define ARPHRD_FRAD 770
#endif
	case ARPHRD_FRAD:
		handle->linktype = DLT_FRELAY;
		break;

	case ARPHRD_LOCALTLK:
		handle->linktype = DLT_LTALK;
		break;

#ifndef ARPHRD_FCPP
#define ARPHRD_FCPP	784
#endif
	case ARPHRD_FCPP:
#ifndef ARPHRD_FCAL
#define ARPHRD_FCAL	785
#endif