From 9c38f171626c2973bd7c47f95912bdb885e9848c Mon Sep 17 00:00:00 2001
From: chris <>
Date: Mon, 21 Oct 2002 10:31:40 +0000
Subject: [PATCH] ""

---
 options.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/options.c b/options.c
index 1520b8f..59cd453 100644
--- a/options.c
+++ b/options.c
@@ -23,6 +23,27 @@ char optstr[] = "+i:f:n:dhpbP";
 
 /* Global options. */
 
+/* Selecting an interface on which to listen: */
+
+/* This is a list of interface name prefixes which are `bad' in the sense
+ * that they don't refer to interfaces of external type on which we are
+ * likely to want to listen. We also compare candidate interfaces to lo. */
+static char *bad_interface_names[] = {
+            "dummy",
+            "vmnet",
+            NULL        /* last entry must be NULL */
+        };
+
+static int is_bad_interface_name(char *i) {
+    char **p;
+    for (p = bad_interface_names; *p; ++p)
+        if (strncmp(i, *p, strlen(*p)) == 0)
+            return 1;
+    return 0;
+}
+
+/* This finds the first interface which is up and is not the loopback
+ * interface or one of the interface types listed in bad_interface_names. */
 static char *get_first_interface(void) {
     int s, size = 1;
     struct ifreq *ifr;
@@ -43,9 +64,7 @@ static char *get_first_interface(void) {
     } while (size * sizeof *ifc.ifc_req <= ifc.ifc_len);
     /* Ugly. */
     for (ifr = ifc.ifc_req; (char*)ifr < (char*)ifc.ifc_req + ifc.ifc_len; ++ifr) {
-        if (strcmp(ifr->ifr_name, "lo") != 0
-            && strncmp(ifr->ifr_name, "dummy", 5) != 0
-            && strncmp(ifr->ifr_name, "vmnet", 5) != 0
+        if (strcmp(ifr->ifr_name, "lo") != 0 && !is_bad_interface_name(ifr->ifr_name)
             && ioctl(s, SIOCGIFFLAGS, ifr) == 0 && ifr->ifr_flags & IFF_UP) {
             i = xstrdup(ifr->ifr_name);
             break;
@@ -137,7 +156,7 @@ static void usage(FILE *fp) {
 "   -p                  run in promiscuous mode (show traffic between other\n"
 "                       hosts on the same network segment)\n"
 "   -b                  don't display a bar graph of traffic\n"
-"   -i interface        listen on named interface (default: eth0)\n"
+"   -i interface        listen on named interface\n"
 "   -f filter code      use filter code to select packets to count\n"
 "                       (default: none, but only IP packets are counted)\n"
 "   -n net/mask         show traffic flows in/out of network\n"