Janus build broken

[fnoop]

  CC       transports/libjanus_websockets_la-janus_websockets.lo
transports/janus_websockets.c: In function ‘janus_websockets_reason_string’:
transports/janus_websockets.c:263:12: error: ‘LWS_CALLBACK_ADD_HEADERS’ undeclared (first use in this function); did you mean ‘LWS_CALLBACK_ADD_POLL_FD’?
   CASE_STR(LWS_CALLBACK_ADD_HEADERS);
            ^~~~~~~~~~~~~~~~~~~~~~~~
transports/janus_websockets.c:244:29: note: in definition of macro ‘CASE_STR’
 #define CASE_STR(name) case name: return #name
                             ^~~~
transports/janus_websockets.c:263:12: note: each undeclared identifier is reported only once for each function it appears in
   CASE_STR(LWS_CALLBACK_ADD_HEADERS);
            ^~~~~~~~~~~~~~~~~~~~~~~~
transports/janus_websockets.c:244:29: note: in definition of macro ‘CASE_STR’
 #define CASE_STR(name) case name: return #name
                             ^~~~
transports/janus_websockets.c: In function ‘janus_websockets_get_interface_name’:
transports/janus_websockets.c:305:30: warning: cast increases required alignment of target type [-Wcast-align]
     struct sockaddr_in *sa = (struct sockaddr_in *)(iap->ifa_addr);
                              ^
transports/janus_websockets.c:314:31: warning: cast increases required alignment of target type [-Wcast-align]
     struct sockaddr_in6 *sa = (struct sockaddr_in6 *)(iap->ifa_addr);
                               ^
transports/janus_websockets.c: In function ‘janus_websockets_common_callback’:
transports/janus_websockets.c:1441:8: error: ‘LWS_CALLBACK_ADD_HEADERS’ undeclared (first use in this function); did you mean ‘LWS_CALLBACK_ADD_POLL_FD’?
   case LWS_CALLBACK_ADD_HEADERS: {
        ^~~~~~~~~~~~~~~~~~~~~~~~
        LWS_CALLBACK_ADD_POLL_FD
transports/janus_websockets.c:1449:30: error: dereferencing pointer to incomplete type ‘struct lws_process_html_args’
       (unsigned char **)&args->p,
                              ^~
transports/janus_websockets.c:1460:37: warning: variable ‘methods’ set but not used [-Wunused-but-set-variable]
     char origin[256], headers[256], methods[256];
                                     ^~~~~~~
transports/janus_websockets.c:1629:17: error: implicit declaration of function ‘lws_write_ws_flags’; did you mean ‘BN_with_flags’? [-Werror=implicit-function-declaration]
     int flags = lws_write_ws_flags(LWS_WRITE_TEXT, ws_client->bufoffset == LWS_PRE, ws_client->bufpending <= (size_t)amount);
                 ^~~~~~~~~~~~~~~~~~
                 BN_with_flags
transports/janus_websockets.c:1629:17: warning: nested extern declaration of ‘lws_write_ws_flags’ [-Wnested-externs]
cc1: some warnings being treated as errors
make[2]: *** [Makefile:2360: transports/libjanus_websockets_la-janus_websockets.lo] Error 1
make[2]: Leaving directory '/srv/maverick/var/build/janus-gateway'
make[1]: *** [Makefile:3401: all-recursive] Error 1
make[1]: Leaving directory '/srv/maverick/var/build/janus-gateway'
make: *** [Makefile:1554: all] Error 2

Looks like Janus is trying to use websocket callback that doesn't exist in the version libwebsockets installed in Raspbian buster (2.0.3). lws api changes quite a bit and Janus requires fairly specific versions, so probably the easiest thing to do is compile lws separately into ~/software and use that.

[fnoop]

Builds but can't find libwebsockets at runtime:

Sep 17 12:19:12 maverick-raspberry systemd[1]: Started WebRTC Janus Gateway.
Sep 17 12:19:12 maverick-raspberry janus[1154]: /srv/maverick/software/janus-gateway/bin/janus: error while loading shared libraries: libwebsockets.so.18: cannot open shared object file: No such file or directory
Sep 17 12:19:12 maverick-raspberry systemd[1]: maverick-webrtc.service: Main process exited, code=exited, status=127/n/a
Sep 17 12:19:12 maverick-raspberry systemd[1]: maverick-webrtc.service: Failed with result 'exit-code'.

[fnoop]

Resolves on the command line:

[dev] [mav@maverick-raspberry /etc/systemd/system]$ ldd /srv/maverick/software/janus-gateway/bin/janus
	linux-vdso.so.1 (0xbeea5000)
	/usr/lib/arm-linux-gnueabihf/libarmmem-${PLATFORM}.so => /usr/lib/arm-linux-gnueabihf/libarmmem-v7l.so (0xb6f50000)
	libwebsockets.so.18 => /srv/maverick/software/libwebsockets/lib/libwebsockets.so.18 (0xb6ef5000)

This is probably because we set LD_LIBRARY_PATH in /etc/profile.d/41-maverick-libwebsockets-ldlibrarypath.sh but this isn't used in systemd. Either we should compile the rpath in, or set the runtime path in the systemd manifest.

[fnoop]

Aargh, we need to add libnice build to ensure we get a supported version of libnice. This uses meson and stupidly installs to an architecture dependent libdir by default, so we can't find pkg-config.
mesonbuild/meson#1972
Answer is to set libdir in the meson step, then we can set PKG_CONFIG_PATH reliably across different platforms.

[fnoop]

janus not finding new libnice libraries at startup:

Sep 18 12:30:46 maverick-raspberry systemd[1]: Started WebRTC Janus Gateway.
Sep 18 12:30:46 maverick-raspberry janus[27636]: /srv/maverick/software/janus-gateway/bin/janus: error while loading shared libraries: libnice.so.10: cannot open shared object file: No such file or directory
Sep 18 12:30:46 maverick-raspberry systemd[1]: maverick-webrtc.service: Main process exited, code=exited, status=127/n/a
Sep 18 12:30:46 maverick-raspberry systemd[1]: maverick-webrtc.service: Failed with result 'exit-code'.

It does resolve them on the command line:

[dev] [mav@maverick-raspberry ~/var/build]$ ldd /srv/maverick/software/janus-gateway/bin/janus
	linux-vdso.so.1 (0xbee4b000)
	/usr/lib/arm-linux-gnueabihf/libarmmem-${PLATFORM}.so => /usr/lib/arm-linux-gnueabihf/libarmmem-v7l.so (0xb6ee1000)
	libwebsockets.so.18 => /srv/maverick/software/libwebsockets/lib/libwebsockets.so.18 (0xb6e86000)
	libconfig.so.9 => /lib/arm-linux-gnueabihf/libconfig.so.9 (0xb6e44000)
	libnice.so.10 => /srv/maverick/software/libnice/lib/libnice.so.10 (0xb6df1000)

So rpath must not be baked into the binary correctly.

[dev] [mav@maverick-raspberry ~/var/build]$ readelf -d  /srv/maverick/software/janus-gateway/bin/janus |grep runpath
 0x0000001d (RUNPATH)                    Library runpath: [/srv/maverick/software/libwebsockets/lib]

Hmm, it is being set at compile time:
"LDFLAGS=-L/srv/maverick/software/libwebsockets/lib -lwebsockets -L/srv/maverick/software/libnice/lib -lnice -Wl,-rpath=/srv/maverick/software/libwebsockets/lib,-rpath=/srv/maverick/software/libnice/lib",

[fnoop]

Fixed:
0x0000001d (RUNPATH) Library runpath: [/srv/maverick/software/libnice/lib:/srv/maverick/software/libwebsockets/lib]