net: Handle different key sizes between address families in flow cache

With the conversion of struct flowi to a union of AF-specific structs, some
operations on the flow cache need to account for the exact size of the key.

Signed-off-by: David Ward <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/flow.h

···
 #ifndef _NET_FLOW_H
 #define _NET_FLOW_H
 
+#include <linux/socket.h>
 #include <linux/in6.h>
 #include <linux/atomic.h>
 
···
 static inline struct flowi *flowidn_to_flowi(struct flowidn *fldn)
 {
 	return container_of(fldn, struct flowi, u.dn);
+}
+
+typedef unsigned long flow_compare_t;
+
+static inline size_t flow_key_size(u16 family)
+{
+	switch (family) {
+	case AF_INET:
+		BUILD_BUG_ON(sizeof(struct flowi4) % sizeof(flow_compare_t));
+		return sizeof(struct flowi4) / sizeof(flow_compare_t);
+	case AF_INET6:
+		BUILD_BUG_ON(sizeof(struct flowi6) % sizeof(flow_compare_t));
+		return sizeof(struct flowi6) / sizeof(flow_compare_t);
+	case AF_DECnet:
+		BUILD_BUG_ON(sizeof(struct flowidn) % sizeof(flow_compare_t));
+		return sizeof(struct flowidn) / sizeof(flow_compare_t);
+	}
+	return 0;
 }
 
 #define FLOW_DIR_IN	0

net/core/flow.c

···
 
 static u32 flow_hash_code(struct flow_cache *fc,
 			  struct flow_cache_percpu *fcp,
-			  const struct flowi *key)
+			  const struct flowi *key,
+			  size_t keysize)
 {
 	const u32 *k = (const u32 *) key;
+	const u32 length = keysize * sizeof(flow_compare_t) / sizeof(u32);
 
-	return jhash2(k, (sizeof(*key) / sizeof(u32)), fcp->hash_rnd)
+	return jhash2(k, length, fcp->hash_rnd)
 		& (flow_cache_hash_size(fc) - 1);
 }
 
-typedef unsigned long flow_compare_t;
-
 /* I hear what you're saying, use memcmp.  But memcmp cannot make
- * important assumptions that we can here, such as alignment and
- * constant size.
+ * important assumptions that we can here, such as alignment.
  */
-static int flow_key_compare(const struct flowi *key1, const struct flowi *key2)
+static int flow_key_compare(const struct flowi *key1, const struct flowi *key2,
+			    size_t keysize)
 {
 	const flow_compare_t *k1, *k1_lim, *k2;
-	const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
-
-	BUILD_BUG_ON(sizeof(struct flowi) % sizeof(flow_compare_t));
 
 	k1 = (const flow_compare_t *) key1;
-	k1_lim = k1 + n_elem;
+	k1_lim = k1 + keysize;
 
 	k2 = (const flow_compare_t *) key2;
 
···
 	struct flow_cache_entry *fle, *tfle;
 	struct hlist_node *entry;
 	struct flow_cache_object *flo;
+	size_t keysize;
 	unsigned int hash;
 
 	local_bh_disable();
···
 
 	fle = NULL;
 	flo = NULL;
+
+	keysize = flow_key_size(family);
+	if (!keysize)
+		goto nocache;
+
 	/* Packet really early in init?  Making flow_cache_init a
 	 * pre-smp initcall would solve this.  --RR */
 	if (!fcp->hash_table)
···
 	if (fcp->hash_rnd_recalc)
 		flow_new_hash_rnd(fc, fcp);
 
-	hash = flow_hash_code(fc, fcp, key);
+	hash = flow_hash_code(fc, fcp, key, keysize);
 	hlist_for_each_entry(tfle, entry, &fcp->hash_table[hash], u.hlist) {
 		if (tfle->net == net &&
 		    tfle->family == family &&
 		    tfle->dir == dir &&
-		    flow_key_compare(key, &tfle->key) == 0) {
+		    flow_key_compare(key, &tfle->key, keysize) == 0) {
 			fle = tfle;
 			break;
 		}
···
 			fle->net = net;
 			fle->family = family;
 			fle->dir = dir;
-			memcpy(&fle->key, key, sizeof(*key));
+			memcpy(&fle->key, key, keysize * sizeof(flow_compare_t));
 			fle->object = NULL;
 			hlist_add_head(&fle->u.hlist, &fcp->hash_table[hash]);
 			fcp->hash_count++;