vty: fix writing empty IP address for unconfigured NSVCs

config_write_bts_gprs() currently writes the remote address of an
NSVC even if osmo_sockaddr_str_from_sockaddr() returns non-zero
code.  Thus saving a configuration with only one configured NSVC
to a file would produce the following:

 bts N
  ...
  gprs nsvc 0 nsvci 101
  gprs nsvc 0 local udp port 23023
  gprs nsvc 0 remote ip 127.0.0.1
  gprs nsvc 0 remote udp port 23000
  gprs nsvc 1 nsvci 0
  gprs nsvc 1 local udp port 0
  gprs nsvc 1 remote ip

and next time osmo-bsc would refuse to start due to:

 Error occurred during reading the below line:
  gprs nsvc 1 remote ip

The related condition consists of the following two parts:

  - checking if osmo_sockaddr_str_from_sockaddr() != 0;
  - checking if 'remote.af != AF_UNSPEC'.

The first one is wrong, because osmo_sockaddr_str_from_sockaddr(),
like many other functions, returns 0 on success.  Let's fix this.

After the fix, the second part does not seem to make sense, because
remote.af would remain AF_UNSPEC (0) if the function call succeeds.

Printing the remote port alone does not make sense, let's avoid
printing it if the address cannot be parsed into a string.

Change-Id: I5d6cbde4f605c8184db4ade87de5644a849c05db
Fixes: I621360cab1e12c22248e33d62a9929995053ce04
1 file changed