version(5) says:
If the server does not understand the client's version
string, it should respond with an Rversion message (not
Rerror) with the version string the 7 characters
``unknown''.
Pre-lib9p file servers -- all except cwfs(4) -- do return Rerror.
lib9p(2) follows the above spec, although ignoring the next part
concerning comparison after period-stripping. It assumes an
Fcall.version starting with "9P" is correctly formed and returns
the only supported version of the protocol, which seems alright.
This patch brings pre-lib9p servers in accordance with the spec.
The mount() and bind() syscalls return -1 on error,
and the mountid sequence number on success.
The manpage states that the mountid sequence number
is a positive integer, but the kernels implementation
currently uses a unsigned 32-bit integer and does not
guarantee that the mountid will not become negative.
Most code just cares about the error, so test for
the -1 error value only.
avoid returning ip addresses that cannot be reached due
to lack of a compatible ip address. this means when here
is no ipv4 address configured, we wont return ipv4 addresses
and would not query dns for an A record.
likewise, when here is no ipv6 address configured then
we wont query dns for an AAAA record.
ipv6 lookups can still be disabled with the -4 flag just
as before.
the dnsquery() library function should not start mouting /srv/dns on
its own. this problem arrises only for ndb/cs as it is started before
ndb/dns.
the issue with mounting /srv/dns before /net is when ndb/cs attempts
to read the list of interfaces, accessing /net/ipifc, which triggers
a rpc to ndb/dns as it is ontop of the mount. this can yield a deadlock
when ndb/dns blocks its 9p loop waiting for requests to complete on
a refresh and the requests are stuck waiting for ndb/cs to translate
a dial string for announce().
we have to maintain the ->line chain for ndbreorder() to work, so add
a little helper: ndbline() which replicates the ->entry chain and links
the last tuple to the first; makeing the whole list into a single line.
when we get eof, stop the loop immidiately and do not
rely on the read to eventually return an error.
when convM2S() fails to decode the message, error out
and stop the loop. there is no point in continuing.
