The RFC says to encode an single empty TXT string instead of an empty
TXT array. It also says to treat a zero-length TXT RR as a TXT array
with a single zero-length string.
TXT records should have at least one character, so enforce this.
Before 0f84a72 parser SIGSEGV'd on ->txt.strings being NULL, but
even if this is fixed we should reject invalid TXT records.
Loops in RR compression were only detected for the first entry.
Multiple redirections should be allowed, each one checking for an
infinite loop on its own starting point.
Also update the pointer on each redirection to avoid longer loops of
labels and redirections, in names like:
(start) [len=1] "A", [ptr to start]
(David: rename variable to "jump_barrier" and add reference to RFC)
It is redundant to store 'hash' and 'compare' function pointers in
struct Hashmap separately. The functions always comprise a pair.
Store a single pointer to struct hash_ops instead.
systemd keeps hundreds of hashmaps, so this saves a little bit of
memory.
Make sure we format UTF-8 labels as IDNA when writing them to DNS
packets, and as native UTF-8 when writing them to mDNS or LLMNR packets.
When comparing or processing labels always consider native UTF-8 and
IDNA formats equivalent.
LOC records have a version field. So far only version 0 has been
published, but if a record with a different version was encountered,
our only recourse is to treat it as an unknown type. This is
implemented with the 'unparseable' flag, which causes the
serialization/deserialization and printing function to cause the
record as a blob. The flag can be used if other packet types cannot be
parsed for whatever reason.
Let's turn resolved into a something truly useful: a fully asynchronous
DNS stub resolver that subscribes to network changes.
(More to come: caching, LLMNR, mDNS/DNS-SD, DNSSEC, IDN, NSS module)
Veres Lajos