mdns: die iff the MDNS advertising process dies

and not if any other child does!

mdns.c

@@ -31,7 +31,7 @@
 #include <unistd.h>
 #include "common.h"
 
-static int mdns_pid = 0;
+int mdns_pid = 0;
 
 void mdns_unregister(void) {
     if (mdns_pid)

mdns.h

@@ -1,6 +1,8 @@
 #ifndef _MDNS_H
 #define _MDNS_H
 
+extern int mdns_pid;
+
 void mdns_unregister(void);
 void mdns_register(void);
 

rtsp.c

@@ -791,7 +791,14 @@ void rtsp_listen_loop(void) {
     printf("Listening for connections.\n");
 
     int acceptfd;
-    while (select(maxfd+1, &fds, 0, 0, 0) >= 0) {
+    while (1) {
+        ret = select(maxfd+1, &fds, 0, 0, 0);
+        if (ret<0) {
+            if (errno==EINTR)
+                continue;
+            break;
+        }
+
         for (i=0; i<nsock; i++) {
             if (FD_ISSET(sockfd[i], &fds)) {
                 acceptfd = sockfd[i];

shairport.c

@@ -28,6 +28,7 @@
 #include <unistd.h>
 #include <memory.h>
 #include <openssl/md5.h>
+#include <sys/wait.h>
 #include "common.h"
 #include "rtsp.h"
 #include "mdns.h"
@@ -50,6 +51,15 @@ static void sig_shutdown(int foo, siginfo_t *bar, void *baz) {
     shairport_shutdown();
 }
 
+static void sig_child(int foo, siginfo_t *bar, void *baz) {
+    pid_t pid;
+    while ((pid = waitpid((pid_t)-1, 0, WNOHANG)) > 0) {
+        if (pid == mdns_pid && !shutting_down) {
+            die("MDNS child process died unexpectedly!");
+        }
+    }
+}
+
 void usage(char *progname) {
     printf("Usage: %s [options...] [-- [output options...]]\n\n", progname);
     printf("Available options:\n"
@@ -128,6 +138,9 @@ void signal_setup(void) {
     sa.sa_sigaction = &sig_shutdown;
     sigaction(SIGINT, &sa, NULL);
     sigaction(SIGTERM, &sa, NULL);
+
+    sa.sa_flags = SA_SIGINFO;
+    sa.sa_sigaction = &sig_child;
     sigaction(SIGCHLD, &sa, NULL);
 }