Subject: [PATCH] Socket filter access to hatype

From: Paul LeoNerd Evans <[email-masked]>
Date: Wed, 21 Apr 2010 18:25:46 +0100

When capturing packets on a PF_PACKET/SOCK_RAW socket bound to all
interfaces, there doesn't appear to be a way for the filter program to
actually find out the underlying hardware type the packet was captured
on, such as is reported by the sll_hatype field of the struct sockaddr_ll
when the packet is sent up to userland.

Unless I've managed to miss a trick somewhere, this would seem to put a
fairly fundamental blocker on actually being able to filter in such
packets. Granted there's the SKF_OFF_NET area to inspect at the e.g. IPv4
level, but this makes it impossible to do anything on e.g. the Ethernet
level.

See below for a patch to add an SKF_AD_HATYPE field, up among the other
special access fields around SKF_AD_OFF.

diff -ur linux-2.6.33.2.orig/include/linux/filter.h linux-2.6.33.2/include/linux/filter.h
--- linux-2.6.33.2.orig/include/linux/filter.h	2010-04-02 00:02:33.000000000 +0100
+++ linux-2.6.33.2/include/linux/filter.h	2010-04-20 22:40:25.000000000 +0100
@@ -123,7 +123,8 @@
 #define SKF_AD_NLATTR_NEST	16
 #define SKF_AD_MARK 	20
 #define SKF_AD_QUEUE	24
-#define SKF_AD_MAX	28
+#define SKF_AD_HATYPE	28
+#define SKF_AD_MAX	32
 #define SKF_NET_OFF   (-0x100000)
 #define SKF_LL_OFF    (-0x200000)
 
diff -ur linux-2.6.33.2.orig/net/core/filter.c linux-2.6.33.2/net/core/filter.c
--- linux-2.6.33.2.orig/net/core/filter.c	2010-04-02 00:02:33.000000000 +0100
+++ linux-2.6.33.2/net/core/filter.c	2010-04-20 22:41:01.000000000 +0100
@@ -309,6 +309,9 @@
 		case SKF_AD_QUEUE:
 			A = skb->queue_mapping;
 			continue;
+		case SKF_AD_HATYPE:
+			A = skb->dev->type;
+			continue;
 		case SKF_AD_NLATTR: {
 			struct nlattr *nla;

-- 
Paul "LeoNerd" Evans

[email-masked]
ICQ# 4135350       |  Registered Linux# 179460
http://www.leonerd.org.uk/