netfilter: nft_tproxy: Fix port selector on Big Endian

On Big Endian architectures, u16 port value was extracted from the wrong
parts of u32 sreg_port, just like commit 1059660 ("netfilter:
nf_tables: fix mismatch in big-endian system") describes.

Fixes: 4ed8eb6 ("netfilter: nf_tables: Add native tproxy support")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Acked-by: Florian Westphal <fw@strlen.de>
Acked-by: Máté Eckl <ecklm94@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_tproxy.c

@@ -50,7 +50,7 @@ static void nft_tproxy_eval_v4(const struct nft_expr *expr,
 	taddr = nf_tproxy_laddr4(skb, taddr, iph->daddr);
 
 	if (priv->sreg_port)
-		tport = regs->data[priv->sreg_port];
+		tport = nft_reg_load16(&regs->data[priv->sreg_port]);
 	if (!tport)
 		tport = hp->dest;
 
@@ -117,7 +117,7 @@ static void nft_tproxy_eval_v6(const struct nft_expr *expr,
 	taddr = *nf_tproxy_laddr6(skb, &taddr, &iph->daddr);
 
 	if (priv->sreg_port)
-		tport = regs->data[priv->sreg_port];
+		tport = nft_reg_load16(&regs->data[priv->sreg_port]);
 	if (!tport)
 		tport = hp->dest;