dnsdist: Add support for range-based lookups into a Key-Value store

[rgacogne]

Short description

This feature allows doing a range-based lookup (mostly useful for IP addresses), assuming that:

• there is a key for the last element of the range (2001:0db8:ffff:ffff:ffff:ffff:ffff:ffff for 2001:db8::/32)
  which contains the first element of the range (2001:0db8:0000:0000:0000:0000:0000:0000) followed by any data in the value
• AND there is no overlapping ranges in the database !!

This requires that the underlying store supports ordered keys, which is true for LMDB but not for CDB, for example.

PS: this PR is based on the work done in #10520 and might require a rebase once it is merged. So you can skip the first two commits on that branch when reviewing :)

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[github-actions]

Misspellings found, please review:

• exampe

To accept these changes, run the following commands from this repository on this branch

pushd $(git rev-parse --show-toplevel)
perl -e '
my @expect_files=qw('".github/actions/spell-check/expect.txt"');
@ARGV=@expect_files;
my @stale=qw('"autohint dnsparser fastopen fff githubusercontent htm issuecomment proxyprotocol smb "');
my $re=join "|", @stale;
my $suffix=".".time();
my $previous="";
sub maybe_unlink { unlink($_[0]) if $_[0]; }
while (<>) {
  if ($ARGV ne $old_argv) { maybe_unlink($previous); $previous="$ARGV$suffix"; rename($ARGV, $previous); open(ARGV_OUT, ">$ARGV"); select(ARGV_OUT); $old_argv = $ARGV; }
  next if /^(?:$re)(?:(?:\r|\n)*$| .*)/; print;
}; maybe_unlink($previous);'
perl -e '
my $new_expect_file=".github/actions/spell-check/expect.txt";
use File::Path qw(make_path);
make_path ".github/actions/spell-check";
open FILE, q{<}, $new_expect_file; chomp(my @words = <FILE>); close FILE;
my @add=qw('"exampe "');
my %items; @items{@words} = @words x (1); @items{@add} = @add x (1);
@words = sort {lc($a) cmp lc($b)} keys %items;
open FILE, q{>}, $new_expect_file; for my $word (@words) { print FILE "$word\n" if $word =~ /\w/; };
close FILE;'
popd

[omoerbeek]

This looks all good to me now. TSAN failure should be investigated.

[rgacogne]

This looks all good to me now.

Thanks, Otto!

TSAN failure should be investigated.

I looked into it, and it seems to be a timing issue (we have a QPS limit that might not match if the test takes too long). It's not related to this PR anyway so I'm going to merge it.

[rgacogne]

Ah, I need to merge 10520 first so I'll wait a bit :)