[SECMARK]: Add secmark support to core networking.

Add a secmark field to the skbuff structure, to allow security subsystems to
place security markings on network packets.  This is similar to the nfmark
field, except is intended for implementing security policy, rather than than
networking policy.

This patch was already acked in principle by Dave Miller.
Signed-off-by: NJames Morris <jmorris@namei.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -210,6 +210,7 @@ enum {
  *	@nf_bridge: Saved data about a bridged frame - see br_netfilter.c
  *	@tc_index: Traffic control index
  *	@tc_verd: traffic control verdict
+ *	@secmark: security marking
  */
 
 struct sk_buff {
@@ -289,6 +290,9 @@ struct sk_buff {
 #ifdef CONFIG_NET_DMA
 	dma_cookie_t		dma_cookie;
 #endif
+#ifdef CONFIG_NETWORK_SECMARK
+	__u32			secmark;
+#endif
 
 
 	/* These elements must be at the end, see alloc_skb() for details.  */
@@ -1400,5 +1404,23 @@ static inline void nf_reset(struct sk_buff *skb)
 static inline void nf_reset(struct sk_buff *skb) {}
 #endif /* CONFIG_NETFILTER */
 
+#ifdef CONFIG_NETWORK_SECMARK
+static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
+{
+	to->secmark = from->secmark;
+}
+
+static inline void skb_init_secmark(struct sk_buff *skb)
+{
+	skb->secmark = 0;
+}
+#else
+static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
+{ }
+
+static inline void skb_init_secmark(struct sk_buff *skb)
+{ }
+#endif
+
 #endif	/* __KERNEL__ */
 #endif	/* _LINUX_SKBUFF_H */

net/Kconfig

@@ -66,6 +66,13 @@ source "net/ipv6/Kconfig"
 
 endif # if INET
 
+config NETWORK_SECMARK
+	bool "Security Marking"
+	help
+	  This enables security marking of network packets, similar
+	  to nfmark, but designated for security purposes.
+	  If you are unsure how to answer this question, answer N.
+
 menuconfig NETFILTER
 	bool "Network packet filtering (replaces ipchains)"
 	---help---

net/core/skbuff.c

@@ -464,7 +464,7 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 	n->tc_verd = CLR_TC_MUNGED(n->tc_verd);
 	C(input_dev);
 #endif
-
+	skb_copy_secmark(n, skb);
 #endif
 	C(truesize);
 	atomic_set(&n->users, 1);
@@ -526,6 +526,7 @@ static void copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 #endif
 	new->tc_index	= old->tc_index;
 #endif
+	skb_copy_secmark(new, old);
 	atomic_set(&new->users, 1);
 	skb_shinfo(new)->tso_size = skb_shinfo(old)->tso_size;
 	skb_shinfo(new)->tso_segs = skb_shinfo(old)->tso_segs;

net/ipv4/ip_output.c

@@ -410,6 +410,7 @@ static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 	nf_bridge_get(to->nf_bridge);
 #endif
 #endif
+	skb_copy_secmark(to, from);
 }
 
 /*

net/ipv4/netfilter/ipt_REJECT.c

@@ -147,6 +147,7 @@ static void send_reset(struct sk_buff *oldskb, int hook)
 	/* This packet will not be the same as the other: clear nf fields */
 	nf_reset(nskb);
 	nskb->nfmark = 0;
+	skb_init_secmark(nskb);
 
 	tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
 

net/ipv6/ip6_output.c

@@ -459,6 +459,7 @@ static void ip6_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 	nf_bridge_get(to->nf_bridge);
 #endif
 #endif
+	skb_copy_secmark(to, from);
 }
 
 int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)