Re: [nft PATCH] evaluate: Reject quoted strings containing only wildcard

[Phil Sutter <phil@nwl.cc>]

On Thu, Sep 24, 2020 at 07:06:39PM +0200, Phil Sutter wrote:
> Fix for an assertion fail when trying to match against an all-wildcard
> interface name:
> 
> | % nft add rule t c iifname '"*"'
> | nft: expression.c:402: constant_expr_alloc: Assertion `(((len) + (8) - 1) / (8)) > 0' failed.
> | zsh: abort      nft add rule t c iifname '"*"'
> 
> Fix this by detecting the string in expr_evaluate_string() and returning
> an error message:
> 
> | % nft add rule t c iifname '"*"'
> | Error: All-wildcard strings are not supported
> | add rule t c iifname "*"
> |                      ^^^
> 

Note that all this is pretty inconsistent: The above happens only for
quoted asterisks. Unquoted ones cause a different error (at least no
assertion fail):

| % nft add rule t c iifname '*'
| Error: datatype mismatch, expected network interface name, expression has type integer
| add rule t c iifname *
|              ~~~~~~~ ^

What puzzles me is that we have:

| wildcard_expr           :       ASTERISK
|                         {
|                                 struct expr *expr;
| 
|                                 expr = constant_expr_alloc(&@$, &integer_type,
|                                                            BYTEORDER_HOST_ENDIAN,
|                                                            0, NULL);
|                                 $$ = prefix_expr_alloc(&@$, expr, 0);
|                         }
|                         ;

Yet when trying to use it as a prefix, it is rejected:

| % nft add rule t c ip saddr '*'
| Error: datatype mismatch, expected IPv4 address, expression has type integer
| add rule t c ip saddr *
|              ~~~~~~~~ ^

So is this wildcard_expr simply broken or didn't I find correct way to use it
yet?

Cheers, Phil