mosquitto: enable websockets, using libwebsockets 3.0.0

A websocket listener is configured on port 9001

The default libwebsockets version in Rocko, 2.1.0, doesn't work with this
mosquitto version; 1.4.14, see:
eclipse-mosquitto/mosquitto#336 (comment)

Therefore install a newer libwebsockets version, 3.0.0, copied from master:
openembedded/meta-openembedded@abead52

Security considerations: by default mosquitto is disabled. When enabled, it
listens on all interfaces, port 1883. Adding a websockets listener on port
9001 doesn't change the level of security.

meta-alternatives/recipes-connectivity/libwebsockets/libwebsockets_3.0.0.bb

@@ -0,0 +1,27 @@
+SUMMARY = "Canonical libwebsockets.org websocket library"
+HOMEPAGE = "https://libwebsockets.org/"
+LICENSE = "LGPL-2.1"
+LIC_FILES_CHKSUM = "file://LICENSE;md5=4ce87f3facb6f911c142c8bef9bfb380"
+
+DEPENDS = "zlib"
+
+S = "${WORKDIR}/git"
+SRCREV = "eaa935a80adb38b5cc4d09ce06ec987b87dcddfa"
+SRC_URI = "git://github.com/warmcat/libwebsockets.git;protocol=https;"
+
+inherit cmake pkgconfig
+
+PACKAGECONFIG ?= "libuv client server http2 ssl"
+PACKAGECONFIG[client] = "-DLWS_WITHOUT_CLIENT=OFF,-DLWS_WITHOUT_CLIENT=ON,"
+PACKAGECONFIG[http2] = "-DLWS_WITH_HTTP2=ON,-DLWS_WITH_HTTP2=OFF,"
+PACKAGECONFIG[ipv6] = "-DLWS_IPV6=ON,-DLWS_IPV6=OFF,"
+PACKAGECONFIG[libev] = "-DLWS_WITH_LIBEV=ON,-DLWS_WITH_LIBEV=OFF,libev"
+PACKAGECONFIG[libuv] = "-DLWS_WITH_LIBUV=ON,-DLWS_WITH_LIBUV=OFF,libuv"
+PACKAGECONFIG[server] = "-DLWS_WITHOUT_SERVER=OFF,-DLWS_WITHOUT_SERVER=ON,"
+PACKAGECONFIG[ssl] = "-DLWS_WITH_SSL=ON,-DLWS_WITH_SSL=OFF,openssl"
+PACKAGECONFIG[testapps] = "-DLWS_WITHOUT_TESTAPPS=OFF,-DLWS_WITHOUT_TESTAPPS=ON,"
+
+PACKAGES =+ "${PN}-testapps"
+
+FILES_${PN}-dev += "${libdir}/cmake"
+FILES_${PN}-testapps += "${datadir}/libwebsockets-test-server/*"

meta-venus/recipes-connectivity/mosquitto/files/0001-config.mk-enable-websockets.patch

@@ -0,0 +1,25 @@
+From 029d6fc74db276b50578b57ee824e3dcd07ad3c5 Mon Sep 17 00:00:00 2001
+From: mpvader <[email protected]>
+Date: Fri, 17 Aug 2018 22:03:07 +0200
+Subject: [PATCH] config.mk: enable websockets
+
+---
+ config.mk | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/config.mk b/config.mk
+index 71f17e5..eef9c84 100644
+--- a/config.mk
++++ b/config.mk
+@@ -65,7 +65,7 @@ WITH_SRV:=yes
+ WITH_UUID:=yes
+
+ # Build with websockets support on the broker.
+-WITH_WEBSOCKETS:=no
++WITH_WEBSOCKETS:=yes
+
+ # Use elliptic keys in broker
+ WITH_EC:=yes
+-- 
+2.7.4
+

meta-venus/recipes-connectivity/mosquitto/files/mosquitto.conf

@@ -1,2 +1,4 @@
 user mosquitto
 port 1883
+listener 9001
+protocol websockets

meta-venus/recipes-connectivity/mosquitto/mosquitto_%.bbappend

@@ -1,9 +1,14 @@
 FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
 
+DEPENDS += "libwebsockets"
+
 SRC_URI += " \
 	file://mosquitto.conf \
+	file://0001-config.mk-enable-websockets.patch \
 "
 
+PR = "2"
+
 INITSCRIPT_PARAMS = "remove"
 
 MOSQUITTO_D = "/data/conf/mosquitto.d"