Re: [s6-dns] is there a particular reason skadns_packet would return NULL errno ENETUNREACH? [manually resent to list]

From: Guillermo <>
Date: Wed, 12 Oct 2022 22:39:10 -0300

El mié, 12 oct 2022 a las 21:10, Amelia Bjornsdottir escribió:
> I'm passing skadns_send an s6dns_domain_t straight out of an
> s6dns_message_rr_srv_t (case 1) or a s6dns_message_rr_mx_t (case 2).Is
> that in packet format or in string format?

Um, neither? As far as I can tell, skadns_send() always takes a domain
name encoded in a s6dns_domain_t object, and the type of resource
record that you want as the "qtype" argument, which go straight to the
"question" section of a DNS query. Objects of types
s6dns_message_rr_srv_t and s6dns_message_rr_mx_t are used for parsing
RRs in the DNS response that skadns_packet() gives you after the
client gets if from skadnsd using skadns_update().

After learning a bit about skadnsd's texclient protocol, looking at
HardenedBSD's truss output, it looks like your program does 3 queries
for SRV RRs, 1 query for an MX RR, 9 queries for A RRs, and 9 queries
for AAAA RRs. I suppose that on OmniOS, the program does the exact
same 22 queries. In both cases you get responses with no error for the
SRV and MX queries. On Vultr's network,the A and AAAA queries all seem
to get a response with a "format error" RCODE, presumably because the
resulting DNS packet is malformed, and on Shaw's network they don't
seem get a response at all. One possible explanation being that, if
packets are really malformed, Shaw's caches might just not bother
responding to them. This:

sendto(17,"\^?!\^A\0\0\^A\0\0\0\0\0\0.perih"...,44,0,NULL,0) = 44 (0x2c)

makes me very suspicious. That looks like a dot followed by the label
"perihelion", i.e. like coming from a s6dns_domain_t object in string

Received on Thu Oct 13 2022 - 03:39:10 CEST

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