readsb: new package

This package is based on dump1090-fa with many modifications. A big
advantage over dump1090-fa is that it can connect to multiple services
like adsbexchange, piaware or fr24feed.

As the idea for this package is mostly to feed other services, the HTML
files to serve via a webserver have not been included. The service(s)
that will be fed by readsb can offer such a webpage instead.

Finally, the init script does not use local variables, as local is
undefined in POSIX.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

utils/readsb/patches/001-network-avoid-segfault-in-freeaddrinfo.patch

@@ -0,0 +1,89 @@
+From 82014a5fa9930b0875e57869265acf011772277c Mon Sep 17 00:00:00 2001
+From: Stijn Tintel <stijn@linux-ipv6.be>
+Date: Sun, 3 May 2020 20:56:58 +0300
+Subject: [PATCH] network: avoid segfault in freeaddrinfo
+
+Calling freeaddrinfo(NULL) when using musl libc causes a segfault.
+
+Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
+---
+ anet.c     | 15 ++++++++++++---
+ net_io.c   |  5 ++++-
+ viewadsb.c |  5 ++++-
+ 3 files changed, 20 insertions(+), 5 deletions(-)
+
+diff --git a/anet.c b/anet.c
+index 5c35ff8..7f01958 100644
+--- a/anet.c
++++ b/anet.c
+@@ -212,7 +212,10 @@ static int anetTcpGenericConnect(char *err, char *addr, char *service, int flags
+             if (ss) {
+                 memcpy(ss, p->ai_addr, sizeof(*ss));
+             }
+-            freeaddrinfo(gai_result);
++            if (gai_result) {
++                freeaddrinfo(gai_result);
++                gai_result = NULL;
++            }
+             return s;
+         }
+ 
+@@ -220,7 +223,10 @@ static int anetTcpGenericConnect(char *err, char *addr, char *service, int flags
+         anetCloseSocket(s);
+     }
+ 
+-    freeaddrinfo(gai_result);
++    if (gai_result) {
++        freeaddrinfo(gai_result);
++        gai_result = NULL;
++    }
+     return ANET_ERR;
+ }
+ 
+@@ -368,7 +374,10 @@ int anetTcpServer(char *err, char *service, char *bindaddr, int *fds, int nfds)
+         fds[i++] = s;
+     }
+ 
+-    freeaddrinfo(gai_result);
++    if (gai_result) {
++        freeaddrinfo(gai_result);
++        gai_result = NULL;
++    }
+     return (i > 0 ? i : ANET_ERR);
+ }
+ 
+diff --git a/net_io.c b/net_io.c
+index 1f4d848..5f59194 100644
+--- a/net_io.c
++++ b/net_io.c
+@@ -3285,7 +3285,10 @@ void cleanupNetwork(void) {
+     for (int i = 0; i < Modes.net_connectors_count; i++) {
+         struct net_connector *con = Modes.net_connectors[i];
+         free(con->address);
+-        freeaddrinfo(con->addr_info);
++        if (con->addr_info) {
++            freeaddrinfo(con->addr_info);
++            con->addr_info = NULL;
++        }
+         if (con->mutex) {
+             pthread_mutex_unlock(con->mutex);
+             pthread_mutex_destroy(con->mutex);
+diff --git a/viewadsb.c b/viewadsb.c
+index 5fc5386..ad7b1bd 100644
+--- a/viewadsb.c
++++ b/viewadsb.c
+@@ -308,7 +308,10 @@ int main(int argc, char **argv) {
+     }
+     // Free local service and client
+     if (s) free(s);
+-    freeaddrinfo(con->addr_info);
++    if (con->addr_info) {
++        freeaddrinfo(con->addr_info);
++        con->addr_info = NULL;
++    }
+     pthread_mutex_unlock(con->mutex);
+     pthread_mutex_destroy(con->mutex);
+     free(con->mutex);
+-- 
+2.26.2
+