Implement patty_ax25_if_ready() to provide a means of testing an
interface's readiness for performing I/O; this may also be used in the
future for some interface drivers which may require occasional keepalive
timers to maintain a link
Rename patty_ax25_if_ready() to if_pending() in src/if.c, as well as in
each driver implementing this method and any direct invocations of said
driver methods
Re-establish broken APRS-IS connections in src/aprs_is.c; when read() or
write() sets errno to EIO, attempt at most 3 times to re-establish the
APRS-IS connection per read()/write() failure; if the maximum number of
attempts is met, the I/O operation is considered a total failure
Fix invalid return in patty_ax25_aprs_is_send() wherein the number of
bytes written to APRS-IS was returned, rather than the number of AX.25
packet bytes; the number of bytes read is the more important value as it
is used later for repeating the frame to promiscuous mode SOCK_RAW
sockets
Implement patty_ax25_aprs_is_send() to be able to encode any outbound UI
frames in TNC2 format, and to send them to a remote APRS-IS server
Other changes:
* Remove unimplemented patty_ax25_aprs_is_printf() declaration
* Remove unimplemented patty_ax25_aprs_is_readline() declaration
Implement an APRS-IS interface type which is capable of receiving all
APRS-IS traffic which can be represented in AX.25 frames; currently,
there are no provisions for handling extended features such as
non-numeric SSIDs, nor a client nor server which facilitate direct
APRS-IS communication. Presently, APRS-IS traffic cannot be sent from
this interface.
Changes:
* Add patty_ax25_aprs_is driver type in src/aprs_is.c
* Implement 'aprs-is' interface configuration type in bin/if.c; make
separate, smaller state machines for handling base interface
config, KISS, and APRS-IS interface config
