ipv6: Implement different admin modes for automatic flow labels

Change the meaning of net.ipv6.auto_flowlabels to provide a mode for
automatic flow labels generation. There are four modes:

0: flow labels are disabled
1: flow labels are enabled, sockets can opt-out
2: flow labels are allowed, sockets can opt-in
3: flow labels are enabled and enforced, no opt-out for sockets

np->autoflowlabel is initialized according to the sysctl value.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 46 insertions, 13 deletions

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 3e334b3..c02c1c0 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -707,36 +707,69 @@ static inline void iph_to_flow_copy_v6addrs(struct flow_keys *flow,
 }
 
 #if IS_ENABLED(CONFIG_IPV6)
+
+/* Sysctl settings for net ipv6.auto_flowlabels */
+#define IP6_AUTO_FLOW_LABEL_OFF		0
+#define IP6_AUTO_FLOW_LABEL_OPTOUT	1
+#define IP6_AUTO_FLOW_LABEL_OPTIN	2
+#define IP6_AUTO_FLOW_LABEL_FORCED	3
+
+#define IP6_AUTO_FLOW_LABEL_MAX		IP6_AUTO_FLOW_LABEL_FORCED
+
+#define IP6_DEFAULT_AUTO_FLOW_LABELS	IP6_AUTO_FLOW_LABEL_OFF
+
 static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
 					__be32 flowlabel, bool autolabel,
 					struct flowi6 *fl6)
 {
-	if (!flowlabel && (autolabel || net->ipv6.sysctl.auto_flowlabels)) {
-		u32 hash;
+	u32 hash;
 
-		hash = skb_get_hash_flowi6(skb, fl6);
+	if (flowlabel ||
+	    net->ipv6.sysctl.auto_flowlabels == IP6_AUTO_FLOW_LABEL_OFF ||
+	    (!autolabel &&
+	     net->ipv6.sysctl.auto_flowlabels != IP6_AUTO_FLOW_LABEL_FORCED))
+		return flowlabel;
 
-		/* Since this is being sent on the wire obfuscate hash a bit
-		 * to minimize possbility that any useful information to an
-		 * attacker is leaked. Only lower 20 bits are relevant.
-		 */
-		hash ^= hash >> 12;
+	hash = skb_get_hash_flowi6(skb, fl6);
 
-		flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
+	/* Since this is being sent on the wire obfuscate hash a bit
+	 * to minimize possbility that any useful information to an
+	 * attacker is leaked. Only lower 20 bits are relevant.
+	 */
+	rol32(hash, 16);
 
-		if (net->ipv6.sysctl.flowlabel_state_ranges)
-			flowlabel |= IPV6_FLOWLABEL_STATELESS_FLAG;
-	}
+	flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
+
+	if (net->ipv6.sysctl.flowlabel_state_ranges)
+		flowlabel |= IPV6_FLOWLABEL_STATELESS_FLAG;
 
 	return flowlabel;
 }
+
+static inline int ip6_default_np_autolabel(struct net *net)
+{
+	switch (net->ipv6.sysctl.auto_flowlabels) {
+	case IP6_AUTO_FLOW_LABEL_OFF:
+	case IP6_AUTO_FLOW_LABEL_OPTIN:
+	default:
+		return 0;
+	case IP6_AUTO_FLOW_LABEL_OPTOUT:
+	case IP6_AUTO_FLOW_LABEL_FORCED:
+		return 1;
+	}
+}
 #else
 static inline void ip6_set_txhash(struct sock *sk) { }
 static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
-					__be32 flowlabel, bool autolabel)
+					__be32 flowlabel, bool autolabel,
+					struct flowi6 *fl6)
 {
 	return flowlabel;
 }
+static inline int ip6_default_np_autolabel(struct net *net)
+{
+	return 0;
+}
 #endif