来源:dnsmasq官网 发布日期:2021-09-09 阅读次数:1546 评论:0





感知时间:2021-09-09 05:56:55






Handle DHCPREBIND requests in the DHCPv6 server code.
Thanks to Aichun Li for spotting this omission, and the initial

Fix bug which caused dnsmasq to lose track of processes forked
to handle TCP DNS connections under heavy load. The code
checked that at least one free process table slot was
available before listening on TCP sockets, but didn't take
into account that more than one TCP connection could
arrive, so that check was not sufficient to ensure that
there would be slots for all new processes. It compounded
this error by silently failing to store the process when
it did run out of slots. Even when this bug is triggered,
all the right things happen, and answers are still returned.
Only under very exceptional circumstances, does the bug
manifest itself: see
Thanks to Tijs Van Buggenhout for finding the conditions under
which the bug manifests itself, and then working out
exactly what was going on.

Major rewrite of the DNS server and domain handling code.
This should be largely transparent, but it drastically
improves performance and reduces memory foot-print when
configuring large numbers domains of the form
Lookup times now grow as log-to-base-2 of the number of domains,
rather than greater than linearly, as before.
The change makes multiple addresses associated with a domain work
It also handles multiple upstream servers for a domain better; using
the same try/retry algorithms as non domain-specific servers. This
also applies to DNSSEC-generated queries.
Finally, some of the oldest and gnarliest code in dnsmasq has had
a significant clean-up. It's far from perfect, but it _is_ better.

Revise resource handling for number of concurrent DNS queries. This
used to have a global limit, but that has a problem when using
different servers for different upstream domains. Queries which are
routed by domain to an upstream server which is not responding will
build up and trigger the limit, which breaks DNS service for
all other domains which could be handled by other servers. The
change is to make the limit per server-group, where a server group
is the set of servers configured for a particular domain. In the
common case, where only default servers are declared, there is
no effective change.

Improve efficiency of DNSSEC. The sharing point for DNSSEC RR data
used to be when it entered the cache, having been validated. After
that queries requiring the KEY or DS records would share the cached
values. There is a common case in dual-stack hosts that queries for
A and AAAA records for the same domain are made simultaneously.
If required keys were not in the cache, this would result in two
requests being sent upstream for the same key data (and all the
subsequent chain-of-trust queries.) Now we combine these requests
and elide the duplicates, resulting in fewer queries upstream
and better performance. To keep a better handle on what's
going on, the "extra" logging mode has been modified to associate
queries and answers for DNSSEC queries in the same way as ordinary
queries. The requesting address and port have been removed from
DNSSEC logging lines, since this is no longer strictly defined.

Connection track mark based DNS query filtering. Thanks to
Etan Kissling for implementing this It extends query filtering
support beyond what is currently possible
with the `--ipset` configuration option, by adding support for:
1) Specifying allowlists on a per-client basis, based on their
associated Linux connection track mark.
2) Dynamic configuration of allowlists via Ubus.
3) Reporting when a DNS query resolves or is rejected via Ubus.
4) DNS name patterns containing wildcards.
Disallowed queries are not forwarded; they are rejected
with a REFUSED error code.

Allow smaller than 64 prefix lengths in synth-domain, with caveats.
--synth-domain=1234:4567::/56,example.com is now valid.

Make domains generated by --synth-domain appear in replies
when in authoritative mode.

Ensure CAP_NET_ADMIN capability is available when
conntrack is configured. Thanks to Yick Xie for spotting
the lack of this.

When --dhcp-hostsfile --dhcp-optsfile and --addn-hosts are
given a directory as argument, define the order in which
files within that directory are read (alphabetical order
of filename). Thanks to Ed Wildgoose for the initial patch
and motivation for this.









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