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.
with the -s flag, we should read 9P messages from
standard *INPUT* (fd 0) and write responses to
standard *OUTPUT* (fd 1).
before these servers where reading from fd 1,
assuming they where both the same files.
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.
maximum file size is 4GB-1 as the file length is stored in
a 32 bit long. make sure it doesnt overflow on write or
or truncate. interpret the file length as unsigned. pass
vlong to readfile()/writefile()/truncfile() so we can
handle overflows and not just ignore the upper bits.
