This can be used to fix device adoption in ESPHome, which uses a long
"package_import_url" string to advertise the location of the sourcecode
for the device's configuration.
When more than one service (just 2) need to be probed for conflict, generation
of the probe packet fail because pbuf is too small!
So OUTPACKET_SIZE renamed to MDNS_OUTPUT_PACKET_SIZE and moved to mdns_opts.h
to allow configuration. Default configuration raise it to 1450 to have enough
space when MDNS_MAX_SERVICES > 1 else it remain 512.
Extract from RFC 6762, chapter 17, Multicast DNS Message Size:
The 1987 DNS specification [RFC1035] restricts DNS messages carried
by UDP to no more than 512 bytes (not counting the IP or UDP
headers). For UDP packets carried over the wide-area Internet in
1987, this was appropriate. For link-local multicast packets on
today's networks, there is no reason to retain this restriction.
Given that the packets are by definition link-local, there are no
Path MTU issues to consider.
Multicast DNS messages carried by UDP may be up to the IP MTU of the
physical interface, less the space required for the IP header (20
bytes for IPv4; 40 bytes for IPv6) and the UDP header (8 bytes).
Signed-off-by: Simon Goldschmidt <goldsimon@gmx.de>
Two new API:
err_t mdns_search_service(const char *name, const char *service, enum mdns_sd_proto proto,
struct netif *netif, search_result_fn_t result_fn, void *arg,
s8_t *request_id);
void mdns_search_stop(s8_t request_id);
One compilation flags:
LWIP_MDNS_SEARCH
One options flags:
MDNS_MAX_REQUESTS
Some structure declarations moved to allow use by callback result function.
Result domain names are early uncompress before calling application callback
because it cannot be made by application itself.
Allow search services with multiples labels included, like '_services._dns-sd'.
Search for `_services._dns-sd._udp.local.` is handled in a special way.
Only `PTR` answers are send back to the application.
The `mdns_search_service()` function won't assert if no more space in `mdns_request`
table, just return an error if too many simultanous requests.
Probe packet creation -> by splitting the definition and the sending
we can use the definition function for probe tiebreaking.
outpkt creation -> by splitting the creation and sending we can use
the creation function for probe tiebreaking.
The host only responded to a probe query via unicast because
according to the RFC, a probe should have the QU bit on.
This is a should and not a must so we need to be careful.
We added multicast probe answering support with the needed timouts.
Avahi for example probes with the QM queries. With this commit the
conflict is resolved.
See below commit messages for more information
mDNS: support for direct and delayed sends
There are two ways to send a response, directly and after a delay.
A probe or an announce msg are now send via the direct way and
all responses are send via the delayed way.
mDNS improved delay vs direct send behavior on questions
All multicast answers are delayed at the moment. While all unicast
answers are send out directly. A unicast answer is send when this
is requested by the QU bit, when a unicast question was send or
when the question originated from a legacy querier.
mDNS: add probe query detection.
If a probe query is detected a direct unicast respond is send.
Independent of the QU/QM bit.
mDNS split delayed multicast msgs into ipv4 and ipv6 buffers.
We are implementing a two resolvers in one (IPv6 and IPv4 together).
For directly send answers, this does not matter. But for delayed
answers, we need to make a separate buffer for both.
mDNS: addr bug, we should not clear full outmsg
memset deleted also the dest_addr and dest_port, which should remain
and is constant. This commit contains a function that resets only the
needed parts of the outmsg struct.
mDNS: do not multicast a rr within one second.
RFC6762 section 6: prevent network flooding. When a multicast packet
is send out, we start a timeout of 1s within this 1 second all
multicast requests are ignored. We do not make a difference between
the records, we set the delay for all records.
mDNS: improved split for unicast vs multicast and direct vs delayed
unicast delayed message are now possible and multicast direct msgs to.
MDNS: changed printfs to lwip debug messages
MDNS: change timeouts from max time to random time
mDNS: send multicast response on QU questions if not multicasted recently.
If a QU question is received, the responder should multicast the
answer if it did not multicast that record within 25% of it's ttl.
we implemented a stripped down version, meaning that we look at the
records as one set and use one timer for all records. So if the
responder multicasted a record within 30s of the QU question it
will respond with a unicast answer. if not, it will respond
multicast.
mDNS: timeouts -> create function for mdns timeout handling
mdns_set_timeout will check if the timer is running or not and will
update the flag to running after starting the timer.
Multicast timeouts were not set everywhere they needed to be. This
is solved.
mulit <-> multi typo fixed.
mDNS: solve commenting and style issues
mDNS: add #if LWIP_IPVx to new code
LWIP_IPV4/6 can be enabled or disabled, all combination should work.
it's more practical to use netif as a wrapper instead of wrapping
netif in the mdns packets. netif contains all information.
Netif is passed along were needed.
MDNS_TTL changed to MDNS_IP_TTL for clarity.
The mDNS RR ttl does not need to be settalbe, this is against the
RFC. RFC6762 states that for rr's with the hostname in them
somewhere, the ttl should be 120s. If it's not in their it should
be 75 minutes and if the answer is send to a legacy dns querier,
it should be no more then 10s.
This patch corrects the ttl behavior to the RFC.
mDNS.c needed to become cleaner. Domain related functions are
moved to the mdns_domain.c util module. The output related
functions are split off (clear separation between defining the
packet and generating the packet). The output functions can
now be found in mdns_out.c.
mDNS move probe question packet generation to mdns_send_outpacket
The probe any questions were added to the pbuf in the send_probe
routine. It is better if we move all pbuf generation to the output
function so later on packets can be delayed etc. keep it all in
one place.
mDNS: move legacy question generation to mdns_send_outpacket
It's better to do the pbuf generation in one place.
Especially important for message delaying etc.
mDNS take out domain related functionality and put in other file.
The mDNS file is getting very big and a lot still needs to be added.
For clarity reasons it's better to split these domain functions
from the main mDNS file.
mDNS split off output related functionality and put in other file
A lot of functions are only needed for the generation of the pbuf,
by separating them into another file we clean up the mdns file.
We only need the mdns_send_outpacket function as interface.
Packet definition is now completely separated from packet
generation.
