net: add and use __skb_get_hash_symmetric_net

Similar to previous patch: apply same logic for
__skb_get_hash_symmetric and let callers pass the netns to the dissector
core.

Existing function is turned into a wrapper to avoid adjusting all
callers, nft_hash.c uses new function.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240608221057.16070-3-fw@strlen.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/skbuff.h

@@ -1498,8 +1498,14 @@ __skb_set_sw_hash(struct sk_buff *skb, __u32 hash, bool is_l4)
 	__skb_set_hash(skb, hash, true, is_l4);
 }
 
+u32 __skb_get_hash_symmetric_net(const struct net *net, const struct sk_buff *skb);
+
+static inline u32 __skb_get_hash_symmetric(const struct sk_buff *skb)
+{
+	return __skb_get_hash_symmetric_net(NULL, skb);
+}
+
 void __skb_get_hash_net(const struct net *net, struct sk_buff *skb);
-u32 __skb_get_hash_symmetric(const struct sk_buff *skb);
 u32 skb_get_poff(const struct sk_buff *skb);
 u32 __skb_get_poff(const struct sk_buff *skb, const void *data,
 		   const struct flow_keys_basic *keys, int hlen);

net/core/flow_dissector.c

@@ -1845,19 +1845,19 @@ EXPORT_SYMBOL(make_flow_keys_digest);
 
 static struct flow_dissector flow_keys_dissector_symmetric __read_mostly;
 
-u32 __skb_get_hash_symmetric(const struct sk_buff *skb)
+u32 __skb_get_hash_symmetric_net(const struct net *net, const struct sk_buff *skb)
 {
 	struct flow_keys keys;
 
 	__flow_hash_secret_init();
 
 	memset(&keys, 0, sizeof(keys));
-	__skb_flow_dissect(NULL, skb, &flow_keys_dissector_symmetric,
+	__skb_flow_dissect(net, skb, &flow_keys_dissector_symmetric,
 			   &keys, NULL, 0, 0, 0, 0);
 
 	return __flow_hash_from_keys(&keys, &hashrnd);
 }
-EXPORT_SYMBOL_GPL(__skb_get_hash_symmetric);
+EXPORT_SYMBOL_GPL(__skb_get_hash_symmetric_net);
 
 /**
  * __skb_get_hash_net: calculate a flow hash

net/netfilter/nft_hash.c

@@ -51,7 +51,8 @@ static void nft_symhash_eval(const struct nft_expr *expr,
 	struct sk_buff *skb = pkt->skb;
 	u32 h;
 
-	h = reciprocal_scale(__skb_get_hash_symmetric(skb), priv->modulus);
+	h = reciprocal_scale(__skb_get_hash_symmetric_net(nft_net(pkt), skb),
+			     priv->modulus);
 
 	regs->data[priv->dreg] = h + priv->offset;
 }