Re: [PATCH nft 2/5] parser_json: move list_add into json_parse_cmd

[Phil Sutter <phil@nwl.cc>]

Hi Florian,

On Thu, Mar 07, 2024 at 01:26:32PM +0100, Florian Westphal wrote:
> The existing parser cannot handle certain inputs.  Example:
> 
>   "map": {
>    "family": "ip",
>    "name": "testmap",
>    "table": "test",
>    "type": "ipv4_addr",
>    "handle": 2,
>    "map": "verdict",
>    "elem": [ [ "*", {
>         "jump": {
>            "target": "testchain"
> [..]
>     },
>     {
>       "chain": {
>         "family": "ip",
>         "table": "test",
>         "name": "testchain",
>         ...
> 
> Problem is that the json input parser does cmd_add at the earliest opportunity.
> 
> For a simple input file defining a table, set, set element and chain, we get
> following transaction:
>  * add table
>  * add set
>  * add setelem
>  * add chain
> 
> This is rejected by the kernel, because the set element references a chain
> that does (not yet) exist.
> 
> Normal input parser only allocates a CMD_ADD request for the table.
> 
> Rest of the transactional commands are created much later, via nft_cmd_expand(),
> which walks "struct table" and then creates the needed CMD_ADD for the objects
> owned by that table.

JSON parser simply does not support nested syntax, like, for instance:

| table test {
| 	map testmap {
| 		type ipv4_addr : verdict
| 		elements = {
| 			"*" : jump testchain
| 		}
| 	}
| 	chain testchain {
| 	}
| }

Your example above is equivalent to the following in standard syntax:

| add table t
| add map t m { type ipv4_addr : verdict; elements = { 10.0.0.1 : jump mychain }; }
| add chain t mychain

It is rejected by nft as well:

| /tmp/input.nft:2:54-61: Error: Could not process rule: No such file or directory
| add map t m { type ipv4_addr : verdict; elements = { 10.0.0.1 : jump mychain }; }
|                                                      ^^^^^^^^

(Note the wrong marker position, an unrelated bug it seems.)

If I swap the 'add map' and 'add chain' commands in input, it is
accepted.

Cheers, Phil