Add options: --cache-size, CacheSize

[candrews]

• Add new clamd and clamscan option --cache-size

This option allows you to set the number of entries the cache can store.

Additionally, introduce CacheSize as a clamd.conf
synonym for --cache-size.

Fixes #876

The default cache size, 65536, results in tree and nodes values of 256, which were the values in tree without this PR. So the default behavior remains unchanged.

@micahsnyder as discussed in Discord: https://discord.com/channels/636023333074370595/636023333074370597/1091052783161053184

[candrews]

I'd love to also add a debug log message when nodes are evicted from the cache.

@micahsnyder (or anyone else), can you please point me to where in cacheset_add

clamav/libclamav/cache.c

Line 372 in 4c5d548

static inline const char *cacheset_add(struct cache_set *cs, unsigned char *md5, size_t size, uint32_t recursion_level)

this log statement can be added? I'm having a very tough time grokking that function.

[candrews]

I've set the nodes per tree and number of trees to the same value (the sqrt of the requested cache size, rounded up). I think this is reasonable.

[candrews]

I have no idea why the "build-windows" check fails, it doesn't seem related to my changes.

The "clang-format / check (clamonacc, (c-thread-pool|fts|priv_fts))" check fails on formatting of files not changed in this PR.

All other checks pass.

[val-ms]

Very nice PR! I only have a few things to request.

Also, our Jenkins build pipeline is broken right now because of an issue with switching from openssl 1.1 to 3.1. I want to make sure I get that fixed before I merge any PR's. But it of course does pass the mac/linux github actions pipelines and local test went well for me.

[candrews]

I've force pushed an update (I'm not sure if you prefer fixup commits or force push updates, so I took a guess) to this PR that addresses all comments.

@micahsnyder how's this PR look now?

[val-ms]

It looks great! I just rebased with the latest commit from main. Will watch it go through our test pipelines next.

[val-ms]

Testing went well. Merging!

[val-ms]

Augh! Just realized the issue number in the commit message was wrong. It actually fixes #876