From e2cb6559586d4b0d0087c326eac0129fe8661382 Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Sat, 20 Jun 2020 22:30:12 +0100
Subject: [PATCH] Thorough clean-up following
 8270648da1eae77db381b848a47d79b85c206e29.

---
 src/dnsmasq.c | 53 ++++++++++++++++++++++++++-------------------------
 1 file changed, 27 insertions(+), 26 deletions(-)

diff --git a/src/dnsmasq.c b/src/dnsmasq.c
index e0197af..2306c48 100644
--- a/src/dnsmasq.c
+++ b/src/dnsmasq.c
@@ -1864,31 +1864,30 @@ static void check_dns_listeners(time_t now)
 	      else
 		{
 		  int i;
+#ifdef HAVE_LINUX_NETWORK
+		  /* The child process inherits the netlink socket, 
+		     which it never uses, but when the parent (us) 
+		     uses it in the future, the answer may go to the 
+		     child, resulting in the parent blocking
+		     forever awaiting the result. To avoid this
+		     the child closes the netlink socket, but there's
+		     a nasty race, since the parent may use netlink
+		     before the child has done the close.
+		     
+		     To avoid this, the parent blocks here until a 
+		     single byte comes back up the pipe, which
+		     is sent by the child after it has closed the
+		     netlink socket. */
+		  
+		  unsigned char a;
+		  read_write(pipefd[0], &a, 1, 1);
+#endif
 
 		  for (i = 0; i < MAX_PROCS; i++)
 		    if (daemon->tcp_pids[i] == 0 && daemon->tcp_pipes[i] == -1)
 		      {
-			char a;
-			(void)a; /* suppress potential unused warning */
-
 			daemon->tcp_pids[i] = p;
 			daemon->tcp_pipes[i] = pipefd[0];
-#ifdef HAVE_LINUX_NETWORK
-			/* The child process inherits the netlink socket, 
-			   which it never uses, but when the parent (us) 
-			   uses it in the future, the answer may go to the 
-			   child, resulting in the parent blocking
-			   forever awaiting the result. To avoid this
-			   the child closes the netlink socket, but there's
-			   a nasty race, since the parent may use netlink
-			   before the child has done the close.
-
-			   To avoid this, the parent blocks here until a 
-			   single byte comes back up the pipe, which
-			   is sent by the child after it has closed the
-			   netlink socket. */
-			while(retry_send(read(pipefd[0], &a, 1)));
-#endif
 			break;
 		      }
 		}
@@ -1920,16 +1919,16 @@ static void check_dns_listeners(time_t now)
 		 terminate the process. */
 	      if (!option_bool(OPT_DEBUG))
 		{
-		  char a = 0;
-		  (void)a; /* suppress potential unused warning */
+#ifdef HAVE_LINUX_NETWORK
+		  /* See comment above re: netlink socket. */
+		  unsigned char a = 0;
+
+		  close(daemon->netlinkfd);
+		  read_write(pipefd[1], &a, 1, 0);
+#endif		  
 		  alarm(CHILD_LIFETIME);
 		  close(pipefd[0]); /* close read end in child. */
 		  daemon->pipe_to_parent = pipefd[1];
-#ifdef HAVE_LINUX_NETWORK
-		  /* See comment above re netlink socket. */
-		  close(daemon->netlinkfd);
-		  while(retry_send(write(pipefd[1], &a, 1)));
-#endif
 		}
 
 	      /* start with no upstream connections. */
@@ -1956,8 +1955,10 @@ static void check_dns_listeners(time_t now)
 		    shutdown(s->tcpfd, SHUT_RDWR);
 		    close(s->tcpfd);
 		  }
+	      
 	      if (!option_bool(OPT_DEBUG))
 		{
+		  close(daemon->pipe_to_parent);
 		  flush_log();
 		  _exit(0);
 		}