[master] Move the check for another server to be earlier

    [rt38078] Move the check for another server to be earlier

    Move the code that checks if there is already a server
    running to be executed earlier in the process.  This
    puts it before the server touches the database which
    should avoid problems with rewriting a database from
    under a running server.

diff --git a/RELNOTES b/RELNOTES
index 70635b0b67fa59d50ced5b027ae7eacaf0e2b058..d7209af35ecf8ae732a4a11f69156e3b87764109 100644 (file)
--- a/RELNOTES
+++ b/RELNOTES
@@ -202,6 +202,13 @@ by Eric Young (eay@cryptsoft.com).
   leae expiration code.
   [ISC-Bugs #38002]
 
+- Move the check for a PID file and process to be before we rewrite the
+  lease file.  This avoids the possibility of starting a second instance
+  of a server which changes the current lease file confusing the first
+  instance.  This check is only included if the admin hasn't disabled PID
+  files.
+  [ISC-Bugs #38078]
+
                        Changes since 4.3.1b1
 
 - Modify the linux and openwrt dhclient scripts to process information

diff --git a/server/dhcpd.c b/server/dhcpd.c
index ff5968c5293cc0f88062c980a1ac89ef9749ce40..edd09ea74d71f5e2e6b750ea66844392d97523db 100644 (file)
--- a/server/dhcpd.c
+++ b/server/dhcpd.c
@@ -621,6 +621,34 @@ main(int argc, char **argv) {
        if (cftest && !lftest) 
                exit(0);
 
+       /*
+        * First part of dealing with pid files.  Check to see if
+        * we should continue running or not.  We run if:
+        * - we are testing the lease file out
+        * - we don't have a pid file to check
+        * - there is no other process running
+        */
+       if ((lftest == 0) && (no_pid_file == ISC_FALSE)) {
+               /*Read previous pid file. */
+               if ((i = open(path_dhcpd_pid, O_RDONLY)) >= 0) {
+                       status = read(i, pbuf, (sizeof pbuf) - 1);
+                       close(i);
+                       if (status > 0) {
+                               pbuf[status] = 0;
+                               pid = atoi(pbuf);
+
+                               /*
+                                * If there was a previous server process and
+                                * it is still running, abort
+                                */
+                               if (!pid ||
+                                   (pid != getpid() && kill(pid, 0) == 0))
+                                       log_fatal("There's already a "
+                                                 "DHCP server running.");
+                       }
+               }
+       }
+
        group_write_hook = group_writer;
 
        /* Start up the database... */
@@ -696,34 +724,15 @@ main(int argc, char **argv) {
        }
  
        /*
-        * Deal with pid files.  If the user told us
-        * not to write a file we don't read one either
+        * Second part of dealing with pid files.  Now
+        * that we have forked we can write our pid if
+        * appropriate.
         */
        if (no_pid_file == ISC_FALSE) {
-               /*Read previous pid file. */
-               if ((i = open (path_dhcpd_pid, O_RDONLY)) >= 0) {
-                       status = read(i, pbuf, (sizeof pbuf) - 1);
-                       close (i);
-                       if (status > 0) {
-                               pbuf[status] = 0;
-                               pid = atoi(pbuf);
-
-                               /*
-                                * If there was a previous server process and
-                                * it is still running, abort
-                                */
-                               if (!pid ||
-                                   (pid != getpid() && kill(pid, 0) == 0))
-                                       log_fatal("There's already a "
-                                                 "DHCP server running.");
-                       }
-               }
-
-               /* Write new pid file. */
                i = open(path_dhcpd_pid, O_WRONLY|O_CREAT|O_TRUNC, 0644);
                if (i >= 0) {
                        sprintf(pbuf, "%d\n", (int) getpid());
-                       IGNORE_RET (write(i, pbuf, strlen(pbuf)));
+                       IGNORE_RET(write(i, pbuf, strlen(pbuf)));
                        close(i);
                } else {
                        log_error("Can't create PID file %s: %m.",