[PATCH] Fix dumping vlan rules

[PATCH] Fix dumping vlan rules

[michael-dev]

From: "M. Braun" <michael-dev@fami-braun.de>

Given the following bridge rules:
1. ip protocol icmp accept
2. ether type vlan vlan type ip ip protocol icmp accept

The are currently both dumped by "nft list ruleset" as
1. ip protocol icmp accept
2. ip protocol icmp accept

Though, the netlink code actually is different

bridge filter FORWARD 4
  [ payload load 2b @ link header + 12 => reg 1 ]
  [ cmp eq reg 1 0x00000008 ]
  [ payload load 1b @ network header + 9 => reg 1 ]
  [ cmp eq reg 1 0x00000001 ]
  [ immediate reg 0 accept ]

bridge filter FORWARD 5 4
  [ payload load 2b @ link header + 12 => reg 1 ]
  [ cmp eq reg 1 0x00000081 ]
  [ payload load 2b @ link header + 16 => reg 1 ]
  [ cmp eq reg 1 0x00000008 ]
  [ payload load 1b @ network header + 9 => reg 1 ]
  [ cmp eq reg 1 0x00000001 ]
  [ immediate reg 0 accept ]

Fix this by avoiding the removal of all vlan statements
in the given example.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
---
 src/payload.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/payload.c b/src/payload.c
index 3bf1ecc..905422a 100644
--- a/src/payload.c
+++ b/src/payload.c
@@ -506,6 +506,18 @@ static bool payload_may_dependency_kill(struct payload_dep_ctx *ctx,
 		     dep->left->payload.desc == &proto_ip6) &&
 		    expr->payload.base == PROTO_BASE_TRANSPORT_HDR)
 			return false;
+		/* Do not kill
+		 *  ether type vlan and vlan type ip and ip protocol icmp
+		 * into
+		 *  ip protocol icmp
+		 * as this lacks ether type vlan.
+		 * More generally speaking, do not kill protocol type
+		 * for stacked protocols if we only have protcol type matches.
+		 */
+		if (dep->left->etype == EXPR_PAYLOAD && dep->op == OP_EQ &&
+		    expr->flags & EXPR_F_PROTOCOL &&
+		    expr->payload.base == dep->left->payload.base)
+			return false;
 		break;
 	}
 
-- 
2.20.1

Re: [PATCH] Fix dumping vlan rules

[Laura Garcia]

CC'ing netfilter.

On Sat, Jul 13, 2019 at 11:10 PM <michael-dev@fami-braun.de> wrote:
>
> From: "M. Braun" <michael-dev@fami-braun.de>
>
> Given the following bridge rules:
> 1. ip protocol icmp accept
> 2. ether type vlan vlan type ip ip protocol icmp accept
>
> The are currently both dumped by "nft list ruleset" as
> 1. ip protocol icmp accept
> 2. ip protocol icmp accept
>
> Though, the netlink code actually is different
>
> bridge filter FORWARD 4
>   [ payload load 2b @ link header + 12 => reg 1 ]
>   [ cmp eq reg 1 0x00000008 ]
>   [ payload load 1b @ network header + 9 => reg 1 ]
>   [ cmp eq reg 1 0x00000001 ]
>   [ immediate reg 0 accept ]
>
> bridge filter FORWARD 5 4
>   [ payload load 2b @ link header + 12 => reg 1 ]
>   [ cmp eq reg 1 0x00000081 ]
>   [ payload load 2b @ link header + 16 => reg 1 ]
>   [ cmp eq reg 1 0x00000008 ]
>   [ payload load 1b @ network header + 9 => reg 1 ]
>   [ cmp eq reg 1 0x00000001 ]
>   [ immediate reg 0 accept ]
>
> Fix this by avoiding the removal of all vlan statements
> in the given example.
>
> Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
> ---
>  src/payload.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/src/payload.c b/src/payload.c
> index 3bf1ecc..905422a 100644
> --- a/src/payload.c
> +++ b/src/payload.c
> @@ -506,6 +506,18 @@ static bool payload_may_dependency_kill(struct payload_dep_ctx *ctx,
>                      dep->left->payload.desc == &proto_ip6) &&
>                     expr->payload.base == PROTO_BASE_TRANSPORT_HDR)
>                         return false;
> +               /* Do not kill
> +                *  ether type vlan and vlan type ip and ip protocol icmp
> +                * into
> +                *  ip protocol icmp
> +                * as this lacks ether type vlan.
> +                * More generally speaking, do not kill protocol type
> +                * for stacked protocols if we only have protcol type matches.
> +                */
> +               if (dep->left->etype == EXPR_PAYLOAD && dep->op == OP_EQ &&
> +                   expr->flags & EXPR_F_PROTOCOL &&
> +                   expr->payload.base == dep->left->payload.base)
> +                       return false;
>                 break;
>         }
>
> --
> 2.20.1
>

Re: [PATCH] Fix dumping vlan rules

[Florian Westphal]

michael-dev@fami-braun.de <michael-dev@fami-braun.de> wrote:
> From: "M. Braun" <michael-dev@fami-braun.de>
> 
> Given the following bridge rules:
> 1. ip protocol icmp accept
> 2. ether type vlan vlan type ip ip protocol icmp accept
> 
> The are currently both dumped by "nft list ruleset" as
> 1. ip protocol icmp accept
> 2. ip protocol icmp accept

Yes, thats a bug, the dependency removal is incorrect.

> +++ b/src/payload.c
> @@ -506,6 +506,18 @@ static bool payload_may_dependency_kill(struct payload_dep_ctx *ctx,
>  		     dep->left->payload.desc == &proto_ip6) &&
>  		    expr->payload.base == PROTO_BASE_TRANSPORT_HDR)
>  			return false;
> +		/* Do not kill
> +		 *  ether type vlan and vlan type ip and ip protocol icmp
> +		 * into
> +		 *  ip protocol icmp
> +		 * as this lacks ether type vlan.
> +		 * More generally speaking, do not kill protocol type
> +		 * for stacked protocols if we only have protcol type matches.
> +		 */
> +		if (dep->left->etype == EXPR_PAYLOAD && dep->op == OP_EQ &&
> +		    expr->flags & EXPR_F_PROTOCOL &&
> +		    expr->payload.base == dep->left->payload.base)
> +			return false;

Can you please add a test case for this problem to
tests/py/bridge/vlan.t so we catch this when messing with dependency
handling in the future?

Also, please submit v2 directly to netfilter-devel@.

Thanks!