Re: does nft 'tcp option ... exists' work?

[Florian Westphal <fw@strlen.de>]

Maciej Żenczykowski <zenczykowski@gmail.com> wrote:
> FYI, I upgraded the router to OpenWrt 23.05.2 with 5.15.137 and it
> doesn't appear to have changed anything, ie. 'tcp option fastopen
> exists' still does not appear to match.
> 
> Also note that I'm putting this in table inet filter postrouting like
> below... but that shouldn't matter should it?

No, this is an endianess bug, on BE the compared byte is always 0.

I suspect this will fix it:

diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -214,7 +214,7 @@ static void nft_exthdr_tcp_eval(const struct nft_expr *expr,
 
 		offset = i + priv->offset;
 		if (priv->flags & NFT_EXTHDR_F_PRESENT) {
-			*dest = 1;
+			nft_reg_store8(dest, 1);
 		} else {
 			if (priv->len % NFT_REG32_SIZE)
 				dest[priv->len / NFT_REG32_SIZE] = 0;
@@ -461,7 +461,7 @@ static void nft_exthdr_dccp_eval(const struct nft_expr *expr,
 		type = bufp[0];
 
 		if (type == priv->type) {
-			*dest = 1;
+			nft_reg_store8(dest, 1);
 			return;
 		}
 
diff --git a/net/netfilter/nft_fib.c b/net/netfilter/nft_fib.c
--- a/net/netfilter/nft_fib.c
+++ b/net/netfilter/nft_fib.c
@@ -145,11 +145,15 @@ void nft_fib_store_result(void *reg, const struct nft_fib *priv,
 	switch (priv->result) {
 	case NFT_FIB_RESULT_OIF:
 		index = dev ? dev->ifindex : 0;
-		*dreg = (priv->flags & NFTA_FIB_F_PRESENT) ? !!index : index;
+		if (priv->flags & NFTA_FIB_F_PRESENT)
+			nft_reg_store8(dreg, !!index);
+		else
+			*dreg = index;
+
 		break;
 	case NFT_FIB_RESULT_OIFNAME:
 		if (priv->flags & NFTA_FIB_F_PRESENT)
-			*dreg = !!dev;
+			nft_reg_store8(dreg, !!dev);
 		else
 			strscpy_pad(reg, dev ? dev->name : "", IFNAMSIZ);
 		break;