Add per interface support for tx_queue_len, Linux only.

Update the ifconfig example output.

bindings/SigarWrapper.pm

@@ -1081,6 +1081,11 @@ use vars qw(%classes %cmds);
          desc => '',
          plat => 'DFL'
       },
+      {
+         name => 'tx_queue_len', type => 'Int',
+         desc => '',
+         plat => 'L'
+      },
     ],
     NetInterfaceStat => [
       {

bindings/ruby/examples/ifconfig.rb

@@ -65,7 +65,8 @@ iflist.each do |ifname|
         " overruns:" + ifstat.tx_overruns.to_s +
         " carrier:" + ifstat.tx_carrier.to_s
 
-    puts "\t" + "collisions:" + ifstat.tx_collisions.to_s
+    puts "\t" + "collisions:" + ifstat.tx_collisions.to_s +
+      " txqueuelen:" + ifconfig.tx_queue_len.to_s
 
     rx_bytes = ifstat.rx_bytes
     tx_bytes = ifstat.tx_bytes

include/sigar.h

@@ -613,6 +613,7 @@ typedef struct {
         flags,
         mtu,
         metric;
+    int tx_queue_len;
 } sigar_net_interface_config_t;
 
 SIGAR_DECLARE(int)

src/sigar.c

@@ -1640,7 +1640,18 @@ int sigar_net_interface_config_get(sigar_t *sigar, const char *name,
         ifconfig->metric = ifr.ifr_metric ? ifr.ifr_metric : 1;
     }
 
-    close(sock);    
+#if defined(SIOCGIFTXQLEN)
+    if (!ioctl(sock, SIOCGIFTXQLEN, &ifr)) {
+        ifconfig->tx_queue_len = ifr.ifr_qlen;
+    } 
+    else {
+        ifconfig->tx_queue_len = -1; /* net-tools behaviour */
+    }
+#else
+    ifconfig->tx_queue_len = -1;
+#endif
+
+    close(sock);
 
     /* XXX can we get a better description like win32? */
     SIGAR_SSTRCPY(ifconfig->description,