Update discussion of network driver rules

git-svn-id: http://svn.linuxfromscratch.org/LFS/branches/6.2/BOOK@7711 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter07/network.xml

@@ -49,16 +49,10 @@
     Udev rules similar to the following:</para>
 
 <screen role="nodump"><userinput>cat &gt; /etc/udev/rules.d/26-network.rules &lt;&lt; "EOF"
-<literal>ACTION=="add", SUBSYSTEM=="net", DRIVER=="?*", SYSFS{address}=="<replaceable>00:e0:4c:12:34:56</replaceable>", NAME="<replaceable>realtek</replaceable>"
-ACTION=="add", SUBSYSTEM=="net", DRIVER=="?*", SYSFS{address}=="<replaceable>00:a0:c9:78:9a:bc</replaceable>", NAME="<replaceable>intel</replaceable>"</literal>
+<literal>ACTION=="add", SUBSYSTEM=="net", SYSFS{address}=="<replaceable>00:e0:4c:12:34:56</replaceable>", NAME="<replaceable>realtek</replaceable>"
+ACTION=="add", SUBSYSTEM=="net", SYSFS{address}=="<replaceable>00:a0:c9:78:9a:bc</replaceable>", NAME="<replaceable>intel</replaceable>"</literal>
 EOF</userinput></screen>
 
-    <para>The DRIVER=="?*" key prevents Udev from attempting to rename 8021Q
-    VLAN interfaces (not available without the Vlan package from
-    <ulink url="http://www.candelatech.com/~greear/vlan/"/>).
-    This is necessary since VLANs have the same MAC address as
-    the real network card.</para>
-
 <!-- Yes, I know that VLANs are beyond BLFS. This is not the reason to get them
      incorrect by default when every distro does this right. -->
  
@@ -79,6 +73,30 @@ EOF</userinput></screen>
     of <quote>eth0</quote> in the network interface configuration files
     below.</para>
 
+    <para>Note that the rules above don't work for every setup. For example,
+    MAC-based rules break when bridges or VLANs are used, because bridges and
+    VLANs have the same MAC address as the network card. One wants to rename
+    only the network card interface, not the bridge or VLAN interface, but the
+    example rule matches both. If you use such virtual interfaces, you have two
+    potential solutions. One is to add the DRIVER=="?*" key after
+    SUBSYSTEM=="net" in MAC-based rules which will stop matching the virtual
+    interfaces.  This is known to fail with some older Ethernet cards because
+    they don't have the DRIVER variable in the uevent and thus the rule does
+    not match with such cards. Another solution is to switch to rules that use
+    the bus position as a key.</para>
+
+    <para>The second known non-working case is with wireless cards using the
+    MadWifi or HostAP drivers, because they create at least two interfaces
+    with the same MAC address and bus position. For example, the Madwifi driver
+    creates both an athX and a wifiX interface where X is a digit.  To
+    disambiguate these cases, add SYSFS{type}=="zzz" after SUBSYSTEM=="net" for
+    each interface that is handled by that driver, where zzz is the output of
+    <userinput>cat /sys/class/net/&lt;interface_name&gt;/type</userinput>.</para>
+
+    <para>There may be other cases where the rules above don't work. Currently,
+    bugs on this topic are still being reported to Linux distributions, and no
+    solution that covers every case is available.</para>
+
   </sect2>
 
   <sect2>