After finally understanding Brian Murrel's code (my fault, not his)

to get interface names from /proc/net/dev on Linux, fix what I broke
of his code and document it.

diff --git a/common/dispatch.c b/common/dispatch.c
index cf22e25094beab6621e10faaf6964ad5a00ee436..0a383a04d48c03f801b2f136530f06a6bf508490 100644 (file)
--- a/common/dispatch.c
+++ b/common/dispatch.c
@@ -42,7 +42,7 @@
 
 #ifndef lint
 static char copyright[] =
-"$Id: dispatch.c,v 1.47.2.8 1999/02/03 19:46:05 mellon Exp $ Copyright (c) 1995, 1996, 1997, 1998, 1999 The Internet Software Consortium.  All rights reserved.\n";
+"$Id: dispatch.c,v 1.47.2.9 1999/02/05 20:23:50 mellon Exp $ Copyright (c) 1995, 1996, 1997, 1998, 1999 The Internet Software Consortium.  All rights reserved.\n";
 #endif /* not lint */
 
 #include "dhcpd.h"
@@ -262,31 +262,38 @@ void discover_interfaces (state)
           with IP addresses of 0.0.0.0 anymore (grumble).   This only
           matters for the DHCP client, of course - the relay agent and
           server should only care about interfaces that are configured
-          with IP addresses anyway. */
+          with IP addresses anyway.
+
+          The PROCDEV_DEVICE (/proc/net/dev) is a kernel-supplied file
+          that, when read, prints a human readable network status.   We
+          extract the names of the network devices by skipping the first
+          two lines (which are header) and then parsing off everything
+          up to the colon in each subsequent line - these lines start
+          with the interface name, then a colon, then a bunch of
+          statistics.   Yes, Virgina, this is a kludge, but you work
+          with what you have. */
 
        if (state == DISCOVER_UNCONFIGURED) {
-               int proc_dev;
+               FILE *proc_dev;
                char buffer [256];
                struct ifreq *tif;
                int skip = 2;
 
-               proc_dev = open (PROCDEV_DEVICE, O_RDONLY);
-               if (proc_dev < 0)
+               proc_dev = fopen (PROCDEV_DEVICE, "r");
+               if (!proc_dev)
                        error ("%s: %m", PROCDEV_DEVICE);
 
-               while (read (proc_dev, buffer, 256) == 256) {
+               while (fgets (buffer, sizeof buffer, proc_dev)) {
                        char *name = buffer;
                        char *sep;
 
-                       /* Skip the first two blocks, which are apparently
-                          some kind of header. */
+                       /* Skip the first two blocks, which are header
+                          lines. */
                        if (skip) {
                                --skip;
                                continue;
                        }
 
-                       /* XXX What if there is no ':'?   Does the device put
-                          a NUL at the end of the name, I hope? XXX */
                        sep = strrchr (buffer, ':');
                        if (sep)
                                *sep = '\0';
@@ -332,7 +339,7 @@ void discover_interfaces (state)
                        tmp -> next = interfaces;
                        interfaces = tmp;
                }
-               close (proc_dev);
+               fclose (proc_dev);
        }
 #endif