Scan /sys/class/net if we have it.

It's a bit easier to scan than /proc/net/dev, as it's a directory.

diff --git a/pcap-linux.c b/pcap-linux.c
index b502821f543a02d4c145acf6969e4579deb5f2ad..4e1a22ee93e6ed2c441e4a7f0a7f39eb9ab77d99 100644 (file)
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -136,6 +136,7 @@ static const char rcsid[] _U_ =
 #include <linux/if_ether.h>
 #include <net/if_arp.h>
 #include <poll.h>
+#include <dirent.h>
 
 /*
  * Got Wireless Extensions?
@@ -1776,7 +1777,7 @@ pcap_stats_linux(pcap_t *handle, struct pcap_stat *stats)
 }
 
 /*
- * Get from "/proc/net/dev" all interfaces listed there; if they're
+ * Get from "/sys/class/net" all interfaces listed there; if they're
  * already in the list of interfaces we have, that won't add another
  * instance, but if they're not, that'll add them.
  *
@@ -1785,8 +1786,133 @@ pcap_stats_linux(pcap_t *handle, struct pcap_stat *stats)
  * although some other types of addresses can be fetched with SIOCGIFADDR,
  * we don't bother with them for now.
  *
- * We also don't fail if we couldn't open "/proc/net/dev"; we just leave
- * the list of interfaces as is.
+ * We also don't fail if we couldn't open "/sys/class/net"; we just leave
+ * the list of interfaces as is, and return 0, so that we can try
+ * scanning /proc/net/dev.
+ */
+static int
+scan_sys_class_net(pcap_if_t **devlistp, char *errbuf)
+{
+       DIR *sys_class_net_d;
+       int fd;
+       struct dirent *ent;
+       char linebuf[512];
+       int linenum;
+       char *p;
+       char name[512]; /* XXX - pick a size */
+       char *q, *saveq;
+       struct ifreq ifrflags;
+       int ret = 1;
+
+       sys_class_net_d = opendir("/sys/class/net");
+       if (sys_class_net_d == NULL && errno == ENOENT)
+               return (0);
+
+       /*
+        * Create a socket from which to fetch interface information.
+        */
+       fd = socket(AF_INET, SOCK_DGRAM, 0);
+       if (fd < 0) {
+               (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+                   "socket: %s", pcap_strerror(errno));
+               return (-1);
+       }
+
+       for (;;) {
+               errno = 0;
+               ent = readdir(sys_class_net_d);
+               if (ent == NULL) {
+                       /*
+                        * Error or EOF; if errno != 0, it's an error.
+                        */
+                       break;
+               }
+
+               /*
+                * Get the interface name.
+                */
+               q = &ent->d_name[0];
+               while (*p != '\0' && isascii(*p) && !isspace(*p)) {
+                       if (*p == ':') {
+                               /*
+                                * This could be the separator between a
+                                * name and an alias number, or it could be
+                                * the separator between a name with no
+                                * alias number and the next field.
+                                *
+                                * If there's a colon after digits, it
+                                * separates the name and the alias number,
+                                * otherwise it separates the name and the
+                                * next field.
+                                */
+                               saveq = q;
+                               while (isascii(*p) && isdigit(*p))
+                                       *q++ = *p++;
+                               if (*p != ':') {
+                                       /*
+                                        * That was the next field,
+                                        * not the alias number.
+                                        */
+                                       q = saveq;
+                               }
+                               break;
+                       } else
+                               *q++ = *p++;
+               }
+               *q = '\0';
+
+               /*
+                * Get the flags for this interface, and skip it if
+                * it's not up.
+                */
+               strncpy(ifrflags.ifr_name, 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;
+
+               /*
+                * Add an entry for this interface, with no addresses.
+                */
+               if (pcap_add_if(devlistp, name, ifrflags.ifr_flags, NULL,
+                   errbuf) == -1) {
+                       /*
+                        * Failure.
+                        */
+                       ret = -1;
+                       break;
+               }
+       }
+       if (errno != 0) {
+               /*
+                * Error reading the directory.
+                */
+               (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+                   "Error reading /sys/class/net: %s",
+                   pcap_strerror(errno));
+               ret = -1;
+       }
+
+       (void)close(fd);
+       (void)closedir(sys_class_net_d);
+       return (ret);
+}
+
+/*
+ * Get from "/proc/net/dev" all interfaces listed there; if they're
+ * already in the list of interfaces we have, that won't add another
+ * instance, but if they're not, that'll add them.
+ *
+ * See comments from scan_sys_class_net().
  */
 static int
 scan_proc_net_dev(pcap_if_t **devlistp, char *errbuf)
@@ -1802,7 +1928,7 @@ scan_proc_net_dev(pcap_if_t **devlistp, char *errbuf)
        int ret = 0;
 
        proc_net_f = fopen("/proc/net/dev", "r");
-       if (proc_net_f == NULL)
+       if (proc_net_f == NULL && errno == ENOENT)
                return (0);
 
        /*
@@ -1923,16 +2049,26 @@ static const char any_descr[] = "Pseudo-device that captures on all interfaces";
 int
 pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
 {
+       int ret;
+
        /*
-        * Read "/proc/net/dev", and add to the list of interfaces all
+        * Read "/sys/class/net", 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,
         * and even getifaddrs() won't return information about
-        * interfaces with no addresses, so you need to read "/proc/net/dev"
+        * interfaces with no addresses, so you need to read "/sys/class/net"
         * to get the names of the rest of the interfaces.
         */
-       if (scan_proc_net_dev(alldevsp, errbuf) == -1)
-               return (-1);
+       ret = scan_sys_class_net(alldevsp, errbuf);
+       if (ret == -1)
+               return (-1);    /* failed */
+       if (ret == 0) {
+               /*
+                * No /sys/class/net; try reading /proc/net/dev instead.
+                */
+               if (scan_proc_net_dev(alldevsp, errbuf) == -1)
+                       return (-1);
+       }
 
        /*
         * Add the "any" device.