Re: Overlength socket paths (was Re: [COMMITTERS] pgsql: Refactor flex and bison make rules)

On 11/29/2012 03:33 PM, Tom Lane wrote:
> I wrote:
>> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>>> Looks like it was. Good catch. What's the best way to fix?
>> So far as I can see, none of the spec-defined EAI_XXX codes map very
>> nicely to "path name too long". Possibly we could return EAI_SYSTEM
>> and set errno to ENAMETOOLONG, but I'm not sure the latter is very
>> portable either.
> I tried this out and found that at least on Linux, gai_strerror() is too
> stupid to pay attention to errno anyway; you just get "System error",
> which is about as unhelpful as it could possibly be. I don't see any
> way that we can get a more specific error message to be printed without
> eliminating use of gai_strerror and providing our own infrastructure for
> reporting getaddrinfo errors. While that wouldn't be incredibly awful
> (we have such infrastructure already for ancient platforms...), it
> still kinda sucks.
>
>> Another line of attack is to just teach getaddrinfo_unix() to malloc its
>> result struct big enough to hold whatever the supplied path is.
> I tried this out too, and found that it doesn't work well, because both
> libpq and the backend expect to be able to copy getaddrinfo results into
> fixed-size SockAddr structs. We could probably fix that by adding
> another layer of pointers and malloc operations, but it would be
> somewhat invasive. Given the lack of prior complaints it's not clear
> to me that it's worth that much trouble --- although getting rid of our
> hard-wired assumptions about the maximum result size from getaddrinfo is
> attractive from a robustness standpoint.
>
> I'm a bit tempted to just replace EAI_FAIL with EAI_MEMORY here, so
> that you'd get messages similar to "Memory allocation failure". That
> might at least point your thoughts in the right direction, whereas
> "Non-recoverable failure in name resolution" certainly conveys nothing
> of use.
>
> Thoughts?

I don't think it's worth a heroic effort. Meanwhile I'll add a check in
the upgrade test module(s) to check for overly long paths likely to give
problems.

cheers

andrew