fad-gifc.c

Windows XP下的抓包程序实现

	if (fd < 0) {
		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "socket: %s", pcap_strerror(errno));
		return (-1);
	}

	/*
	 * Start with an 8K buffer, and keep growing the buffer until
	 * we have more than "sizeof(ifrp->ifr_name) + MAX_SA_LEN"
	 * bytes left over in the buffer or we fail to get the
	 * interface list for some reason other than EINVAL (which is
	 * presumed here to mean "buffer is too small").
	 */
	buf_size = 8192;
	for (;;) {
		buf = malloc(buf_size);
		if (buf == NULL) {
			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "malloc: %s", pcap_strerror(errno));
			(void)close(fd);
			return (-1);
		}

		ifc.ifc_len = buf_size;
		ifc.ifc_buf = buf;
		memset(buf, 0, buf_size);
		if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0
		    && errno != EINVAL) {
			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "SIOCGIFCONF: %s", pcap_strerror(errno));
			(void)close(fd);
			free(buf);
			return (-1);
		}
		if (ifc.ifc_len < buf_size &&
		    (buf_size - ifc.ifc_len) > sizeof(ifrp->ifr_name) + MAX_SA_LEN)
			break;
		free(buf);
		buf_size *= 2;
	}

	ifrp = (struct ifreq *)buf;
	ifend = (struct ifreq *)(buf + ifc.ifc_len);

	for (; ifrp < ifend; ifrp = ifnext) {
		/*
		 * XXX - what if this isn't an IPv4 address?  Can
		 * we still get the netmask, etc. with ioctls on
		 * an IPv4 socket?
		 *
		 * The answer is probably platform-dependent, and
		 * if the answer is "no" on more than one platform,
		 * the way you work around it is probably platform-
		 * dependent as well.
		 */
		n = SA_LEN(&ifrp->ifr_addr) + sizeof(ifrp->ifr_name);
		if (n < sizeof(*ifrp))
			ifnext = ifrp + 1;
		else
			ifnext = (struct ifreq *)((char *)ifrp + n);

		/*
		 * XXX - The 32-bit compatibility layer for Linux on IA-64
		 * is slightly broken. It correctly converts the structures
		 * to and from kernel land from 64 bit to 32 bit but 
		 * doesn't update ifc.ifc_len, leaving it larger than the 
		 * amount really used. This means we read off the end 
		 * of the buffer and encounter an interface with an 
		 * "empty" name. Since this is highly unlikely to ever 
		 * occur in a valid case we can just finish looking for 
		 * interfaces if we see an empty name.
		 */
		if (!(*ifrp->ifr_name))
			break;

		/*
		 * Skip entries that begin with "dummy".
		 * XXX - what are these?  Is this Linux-specific?
		 * Are there platforms on which we shouldn't do this?
		 */
		if (strncmp(ifrp->ifr_name, "dummy", 5) == 0)
			continue;

		/*
		 * Get the flags for this interface, and skip it if it's
		 * not up.
		 */
		strncpy(ifrflags.ifr_name, ifrp->ifr_name,
		    sizeof(ifrflags.ifr_name));
		if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifrflags) < 0) {
			if (errno == ENXIO)
				continue;
			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "SIOCGIFFLAGS: %.*s: %s",
			    (int)sizeof(ifrflags.ifr_name),
			    ifrflags.ifr_name,
			    pcap_strerror(errno));
			ret = -1;
			break;
		}
		if (!(ifrflags.ifr_flags & IFF_UP))
			continue;

		/*
		 * Get the netmask for this address on this interface.
		 */
		strncpy(ifrnetmask.ifr_name, ifrp->ifr_name,
		    sizeof(ifrnetmask.ifr_name));
		memcpy(&ifrnetmask.ifr_addr, &ifrp->ifr_addr,
		    sizeof(ifrnetmask.ifr_addr));
		if (ioctl(fd, SIOCGIFNETMASK, (char *)&ifrnetmask) < 0) {
			if (errno == EADDRNOTAVAIL) {
				/*
				 * Not available.
				 */
				netmask = NULL;
				netmask_size = 0;
			} else {
				(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
				    "SIOCGIFNETMASK: %.*s: %s",
				    (int)sizeof(ifrnetmask.ifr_name),
				    ifrnetmask.ifr_name,
				    pcap_strerror(errno));
				ret = -1;
				break;
			}
		} else {
			netmask = &ifrnetmask.ifr_addr;
			netmask_size = SA_LEN(netmask);
		}

		/*
		 * Get the broadcast address for this address on this
		 * interface (if any).
		 */
		if (ifrflags.ifr_flags & IFF_BROADCAST) {
			strncpy(ifrbroadaddr.ifr_name, ifrp->ifr_name,
			    sizeof(ifrbroadaddr.ifr_name));
			memcpy(&ifrbroadaddr.ifr_addr, &ifrp->ifr_addr,
			    sizeof(ifrbroadaddr.ifr_addr));
			if (ioctl(fd, SIOCGIFBRDADDR,
			    (char *)&ifrbroadaddr) < 0) {
				if (errno == EADDRNOTAVAIL) {
					/*
					 * Not available.
					 */
					broadaddr = NULL;
					broadaddr_size = 0;
				} else {
					(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
					    "SIOCGIFBRDADDR: %.*s: %s",
					    (int)sizeof(ifrbroadaddr.ifr_name),
					    ifrbroadaddr.ifr_name,
					    pcap_strerror(errno));
					ret = -1;
					break;
				}
			} else {
				broadaddr = &ifrbroadaddr.ifr_broadaddr;
				broadaddr_size = SA_LEN(broadaddr);
			}
		} else {
			/*
			 * Not a broadcast interface, so no broadcast
			 * address.
			 */
			broadaddr = NULL;
			broadaddr_size = 0;
		}

		/*
		 * Get the destination address for this address on this
		 * interface (if any).
		 */
		if (ifrflags.ifr_flags & IFF_POINTOPOINT) {
			strncpy(ifrdstaddr.ifr_name, ifrp->ifr_name,
			    sizeof(ifrdstaddr.ifr_name));
			memcpy(&ifrdstaddr.ifr_addr, &ifrp->ifr_addr,
			    sizeof(ifrdstaddr.ifr_addr));
			if (ioctl(fd, SIOCGIFDSTADDR,
			    (char *)&ifrdstaddr) < 0) {
				if (errno == EADDRNOTAVAIL) {
					/*
					 * Not available.
					 */
					dstaddr = NULL;
					dstaddr_size = 0;
				} else {
					(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
					    "SIOCGIFDSTADDR: %.*s: %s",
					    (int)sizeof(ifrdstaddr.ifr_name),
					    ifrdstaddr.ifr_name,
					    pcap_strerror(errno));
					ret = -1;
					break;
				}
			} else {
				dstaddr = &ifrdstaddr.ifr_dstaddr;
				dstaddr_size = SA_LEN(dstaddr);
			}
		} else {
			/*
			 * Not a point-to-point interface, so no destination
			 * address.
			 */
			dstaddr = NULL;
			dstaddr_size = 0;
		}

#if defined (HAVE_SOLARIS) || defined (HAVE_HPUX10_20_OR_LATER)
		/*
		 * If this entry has a colon followed by a number at
		 * the end, it's a logical interface.  Those are just
		 * the way you assign multiple IP addresses to a real
		 * interface, so an entry for a logical interface should
		 * be treated like the entry for the real interface;
		 * we do that by stripping off the ":" and the number.
		 */
		p = strchr(ifrp->ifr_name, ':');
		if (p != NULL) {
			/*
			 * We have a ":"; is it followed by a number?
			 */
			q = p + 1;
			while (isdigit((unsigned char)*q))
				q++;
			if (*q == '\0') {
				/*
				 * All digits after the ":" until the end.
				 * Strip off the ":" and everything after
				 * it.
				 */
				*p = '\0';
			}
		}
#endif

		/*
		 * Add information for this address to the list.
		 */
		if (add_addr_to_iflist(&devlist, ifrp->ifr_name,
		    ifrflags.ifr_flags, &ifrp->ifr_addr,
		    SA_LEN(&ifrp->ifr_addr), netmask, netmask_size,
		    broadaddr, broadaddr_size, dstaddr, dstaddr_size,
		    errbuf) < 0) {
			ret = -1;
			break;
		}
	}
	free(buf);

#ifdef HAVE_PROC_NET_DEV
	if (ret != -1) {
		/*
		 * We haven't had any errors yet; now read "/proc/net/dev",
		 * and add to the list of interfaces all interfaces listed
		 * there that we don't already have, because, on Linux,
		 * SIOCGIFCONF reports only interfaces with IPv4 addresses,
		 * so you need to read "/proc/net/dev" to get the names of
		 * the rest of the interfaces.
		 */
		ret = scan_proc_net_dev(&devlist, fd, errbuf);
	}
#endif
	(void)close(fd);

	if (ret != -1) {
		/*
		 * We haven't had any errors yet; do any platform-specific
		 * operations to add devices.
		 */
		if (pcap_platform_finddevs(&devlist, errbuf) < 0)
			ret = -1;
	}

	if (ret == -1) {
		/*
		 * We had an error; free the list we've been constructing.
		 */
		if (devlist != NULL) {
			pcap_freealldevs(devlist);
			devlist = NULL;
		}
	}

	*alldevsp = devlist;
	return (ret);
}