nft: track each register individually

Instead of assuming only one register is used, track all 16 regs
individually.

This avoids need for the 'PREV_PAYLOAD' hack and also avoids the need to
clear out old flags:

When we see that register 'x' will be written to, that register state is
reset automatically.

Existing dissector decodes
ip saddr 1.2.3.4 meta l4proto tcp
... as
-s 6.0.0.0 -p tcp

iptables-nft -s 1.2.3.4 -p tcp is decoded correctly because the expressions
are ordered like:

meta l4proto tcp ip saddr 1.2.3.4
                                                                                                                                                                                                                   |
... and 'meta l4proto' did clear the PAYLOAD flag.

The simpler fix is:
		ctx->flags &= ~NFT_XT_CTX_PAYLOAD;

in nft_parse_cmp(), but that breaks dissection of '1-42', because
the second compare ('cmp lte 42') will not find the
payload expression anymore.

Link: https://lore.kernel.org/netfilter-devel/20220922143544.GA22541@breakpoint.cc/T/#t
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Phil Sutter <phil@nwl.cc>

1 files changed, 18 insertions, 18 deletions

diff --git a/iptables/nft-ipv6.c b/iptables/nft-ipv6.c
index 0ab1f971..05d65fbb 100644
--- a/iptables/nft-ipv6.c
+++ b/iptables/nft-ipv6.c
@@ -104,10 +104,12 @@ static bool nft_ipv6_is_same(const struct iptables_command_state *a,
 				  b->fw6.ipv6.outiface_mask);
 }
 
-static void nft_ipv6_parse_meta(struct nft_xt_ctx *ctx, struct nftnl_expr *e,
+static void nft_ipv6_parse_meta(struct nft_xt_ctx *ctx,
+				const struct nft_xt_ctx_reg *reg,
+				struct nftnl_expr *e,
 				struct iptables_command_state *cs)
 {
-	switch (ctx->meta.key) {
+	switch (reg->meta_dreg.key) {
 	case NFT_META_L4PROTO:
 		cs->fw6.ipv6.proto = nftnl_expr_get_u8(e, NFTNL_EXPR_CMP_DATA);
 		if (nftnl_expr_get_u32(e, NFTNL_EXPR_CMP_OP) == NFT_CMP_NEQ)
@@ -117,17 +119,19 @@ static void nft_ipv6_parse_meta(struct nft_xt_ctx *ctx, struct nftnl_expr *e,
 		break;
 	}
 
-	parse_meta(ctx, e, ctx->meta.key, cs->fw6.ipv6.iniface,
+	parse_meta(ctx, e, reg->meta_dreg.key, cs->fw6.ipv6.iniface,
 		   cs->fw6.ipv6.iniface_mask, cs->fw6.ipv6.outiface,
 		   cs->fw6.ipv6.outiface_mask, &cs->fw6.ipv6.invflags);
 }
 
-static void parse_mask_ipv6(struct nft_xt_ctx *ctx, struct in6_addr *mask)
+static void parse_mask_ipv6(const struct nft_xt_ctx_reg *reg,
+			    struct in6_addr *mask)
 {
-	memcpy(mask, ctx->bitwise.mask, sizeof(struct in6_addr));
+	memcpy(mask, reg->bitwise.mask, sizeof(struct in6_addr));
 }
 
 static void nft_ipv6_parse_payload(struct nft_xt_ctx *ctx,
+				   const struct nft_xt_ctx_reg *reg,
 				   struct nftnl_expr *e,
 				   struct iptables_command_state *cs)
 {
@@ -135,17 +139,15 @@ static void nft_ipv6_parse_payload(struct nft_xt_ctx *ctx,
 	uint8_t proto;
 	bool inv;
 
-	switch (ctx->payload.offset) {
+	switch (reg->payload.offset) {
 	case offsetof(struct ip6_hdr, ip6_src):
 		get_cmp_data(e, &addr, sizeof(addr), &inv);
 		memcpy(cs->fw6.ipv6.src.s6_addr, &addr, sizeof(addr));
-		if (ctx->flags & NFT_XT_CTX_BITWISE) {
-			parse_mask_ipv6(ctx, &cs->fw6.ipv6.smsk);
-			ctx->flags &= ~NFT_XT_CTX_BITWISE;
-		} else {
+		if (reg->bitwise.set)
+			parse_mask_ipv6(reg, &cs->fw6.ipv6.smsk);
+		else
 			memset(&cs->fw6.ipv6.smsk, 0xff,
-			       min(ctx->payload.len, sizeof(struct in6_addr)));
-		}
+			       min(reg->payload.len, sizeof(struct in6_addr)));
 
 		if (inv)
 			cs->fw6.ipv6.invflags |= IP6T_INV_SRCIP;
@@ -153,13 +155,11 @@ static void nft_ipv6_parse_payload(struct nft_xt_ctx *ctx,
 	case offsetof(struct ip6_hdr, ip6_dst):
 		get_cmp_data(e, &addr, sizeof(addr), &inv);
 		memcpy(cs->fw6.ipv6.dst.s6_addr, &addr, sizeof(addr));
-		if (ctx->flags & NFT_XT_CTX_BITWISE) {
-			parse_mask_ipv6(ctx, &cs->fw6.ipv6.dmsk);
-			ctx->flags &= ~NFT_XT_CTX_BITWISE;
-		} else {
+		if (reg->bitwise.set)
+			parse_mask_ipv6(reg, &cs->fw6.ipv6.dmsk);
+		else
 			memset(&cs->fw6.ipv6.dmsk, 0xff,
-			       min(ctx->payload.len, sizeof(struct in6_addr)));
-		}
+			       min(reg->payload.len, sizeof(struct in6_addr)));
 
 		if (inv)
 			cs->fw6.ipv6.invflags |= IP6T_INV_DSTIP;