Address joining pitfall

[Menno Smits]

Hi all,

While testing something completely unrelated today I noticed that the
rsyslog worker was continually failing to start for one of the machines in
the environment I was using. When I investigated, I found that the root
cause was that the worker was  trying to connect to the state servers with
an invalid IPv6 address and port combination (I recently enabled IPv6 on my
notebook and home network). As you probably know, IPv6 addresses look
something like "fe80::fcb3:4ff:fe6c:ecd3" but what you might not have
realised is that the correct way to add a port number to a IPv6 address is
to use square brackets like this: "[fe80::fcb3:4ff:fe6c:ecd3]:80"
(otherwise - due to IPv6 address contraction it is unclear whether the port
is the port number or the end of the address). Various Go "net" package
functions will return errors if IPv6 address:port pairs are given without
the square brackets.

The rsyslog worker was joining the address to the port like this:
fmt.Sprintf("%s:%d", host, port) which works fine for hostnames and IPv4
addresses but does the wrong thing for IPv6 addresses. The right tool for
the job is net.JoinHostPort which will do the right thing with all address
types.

I've fixed the rsyslog worker but have found a number of other places in
the code that look like they could suffer from the same problem. Given that
IPv6 adoption is increasing[1] we need to fix these areas before Juju's
users encounter problems when using Juju with IPv6 networks. Here's what I
found:

provider/local/config.go:       return fmt.Sprintf("%s:%d",
c.bootstrapIPAddress(), c.storagePort())
provider/manual/config.go:      return fmt.Sprintf("%s:%d",
c.bootstrapHost(), c.storagePort())
provider/manual/config.go:      return fmt.Sprintf("%s:%d",
c.storageListenIPAddress(), c.storagePort())
state/address.go:               newAddrs[i] = fmt.Sprintf("%s:%d", addr,
port)
state/backups/backups_linux.go: memberHostPort := fmt.Sprintf("%s:%d",
args.PrivateAddress, ssi.StatePort)
state/backups/restore_test.go:  c.Assert(dialInfo.Addrs, gc.DeepEquals,
[]string{fmt.Sprintf("%s:%d", privateAddress, statePort)})
state/backups/restore.go:       Addrs: []string{fmt.Sprintf("%s:%d",
privateAddr, ssi.StatePort)},
utils/ssh/ssh_gocrypto.go:      addr: fmt.Sprintf("%s:%d", host, port),

Can people who are familiar with each of these areas please take a look,
fixing and testing when appropriate.

And for future work, please remember: just use net.JoinHostPort..

- Menno

[1] - on the public internet at least:
https://www.google.com/intl/en/ipv6/statistics.html
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