[master] Add option to suppress the use of fsync when writing lease files

The option is dont-use-async <flag> and it defaults to disabled.

diff --git a/RELNOTES b/RELNOTES
index a99ec5fd1adc2c432db4b0ffbb1c51cd8a93a9fd..48097249a58b590ca87888f8ae0ac7b06f79a380 100644 (file)
--- a/RELNOTES
+++ b/RELNOTES
@@ -89,6 +89,13 @@ work on other platforms. Please report any problems and suggested fixes to
   key for security reasons.
   [ISC-Bugs 30461]
 
+- Add a configuration option to the server to suppress using fsync().
+  Enabling this option will mean that fsync() is never called.  This
+  may provide better performance but there is also a risk that a lease
+  will not be properly written to the disk after it has been issued
+  to a client and before the server stops.  Using this option is
+  not recommended.
+
                        Changes since 4.2.5
 
 - Address static analysis warnings.

diff --git a/includes/dhcpd.h b/includes/dhcpd.h
index 9e18818b8604535ef10eea46457420b56c27ecd0..6a538555fc624ecc6773daca54c02e7dd96bc54a 100644 (file)
--- a/includes/dhcpd.h
+++ b/includes/dhcpd.h
@@ -732,6 +732,7 @@ struct lease_state {
 #endif
 #endif
 #define SV_CACHE_THRESHOLD             78
+#define SV_DONT_USE_FSYNC              79
 
 #if !defined (DEFAULT_PING_TIMEOUT)
 # define DEFAULT_PING_TIMEOUT 1
@@ -1916,6 +1917,7 @@ extern struct timeval cur_tv;
 #define cur_time cur_tv.tv_sec
 
 extern int ddns_update_style;
+extern int dont_use_fsync;
 
 extern const char *path_dhcpd_conf;
 extern const char *path_dhcpd_db;

diff --git a/server/db.c b/server/db.c
index 94abfbde7c3226ba01541bb4227d27036273efac..0b25316b52f8b05ae45be058930f21ddf9152489 100644 (file)
--- a/server/db.c
+++ b/server/db.c
@@ -1014,12 +1014,13 @@ int commit_leases ()
           We need to do this even if we're rewriting the file below,
           just in case the rewrite fails. */
        if (fflush (db_file) == EOF) {
-               log_info ("commit_leases: unable to commit, fflush(): %m");
-               return 0;
+               log_info("commit_leases: unable to commit, fflush(): %m");
+               return (0);
        }
-       if (fsync (fileno (db_file)) < 0) {
+       if ((dont_use_fsync == 0) &&
+           (fsync(fileno (db_file)) < 0)) {
                log_info ("commit_leases: unable to commit, fsync(): %m");
-               return 0;
+               return (0);
        }
 
        /* send out all deferred ACKs now */
@@ -1031,9 +1032,9 @@ int commit_leases ()
        if (count && cur_time - write_time > LEASE_REWRITE_PERIOD) {
                count = 0;
                write_time = cur_time;
-               new_lease_file ();
+               new_lease_file();
        }
-       return 1;
+       return (1);
 }
 
 /*

diff --git a/server/dhcpd.c b/server/dhcpd.c
index 29d4f527dda0ecda4971c6ae11b62351cfd15d45..3588349febafd4dfdd7c323697e414597af1f4ae 100644 (file)
--- a/server/dhcpd.c
+++ b/server/dhcpd.c
@@ -78,6 +78,7 @@ option server.ddns-rev-domainname = \"in-addr.arpa.\";";
 
 #endif /* NSUPDATE */
 int ddns_update_style;
+int dont_use_fsync = 0; /* 0 = default, use fsync, 1 = don't use fsync */
 
 const char *path_dhcpd_conf = _PATH_DHCPD_CONF;
 const char *path_dhcpd_db = _PATH_DHCPD_DB;
@@ -800,7 +801,7 @@ main(int argc, char **argv) {
 
 void postconf_initialization (int quiet)
 {
-       struct option_state *options = (struct option_state *)0;
+       struct option_state *options = NULL;
        struct data_string db;
        struct option_cache *oc;
        char *s;
@@ -808,39 +809,35 @@ void postconf_initialization (int quiet)
        int tmp;
 
        /* Now try to get the lease file name. */
-       option_state_allocate (&options, MDL);
+       option_state_allocate(&options, MDL);
 
        execute_statements_in_scope(NULL, NULL, NULL, NULL, NULL,
                                    options, &global_scope, root_group,
                                    NULL, NULL);
-       memset (&db, 0, sizeof db);
-       oc = lookup_option (&server_universe, options, SV_LEASE_FILE_NAME);
+       memset(&db, 0, sizeof db);
+       oc = lookup_option(&server_universe, options, SV_LEASE_FILE_NAME);
        if (oc &&
-           evaluate_option_cache (&db, (struct packet *)0,
-                                  (struct lease *)0, (struct client_state *)0,
-                                  options, (struct option_state *)0,
-                                  &global_scope, oc, MDL)) {
-               s = dmalloc (db.len + 1, MDL);
+           evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                 &global_scope, oc, MDL)) {
+               s = dmalloc(db.len + 1, MDL);
                if (!s)
-                       log_fatal ("no memory for lease db filename.");
-               memcpy (s, db.data, db.len);
-               s [db.len] = 0;
-               data_string_forget (&db, MDL);
+                       log_fatal("no memory for lease db filename.");
+               memcpy(s, db.data, db.len);
+               s[db.len] = 0;
+               data_string_forget(&db, MDL);
                path_dhcpd_db = s;
        }
 
-       oc = lookup_option (&server_universe, options, SV_PID_FILE_NAME);
+       oc = lookup_option(&server_universe, options, SV_PID_FILE_NAME);
        if (oc &&
-           evaluate_option_cache (&db, (struct packet *)0,
-                                  (struct lease *)0, (struct client_state *)0,
-                                  options, (struct option_state *)0,
-                                  &global_scope, oc, MDL)) {
-               s = dmalloc (db.len + 1, MDL);
+           evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                 &global_scope, oc, MDL)) {
+               s = dmalloc(db.len + 1, MDL);
                if (!s)
-                       log_fatal ("no memory for pid filename.");
-               memcpy (s, db.data, db.len);
-               s [db.len] = 0;
-               data_string_forget (&db, MDL);
+                       log_fatal("no memory for pid filename.");
+               memcpy(s, db.data, db.len);
+               s[db.len] = 0;
+               data_string_forget(&db, MDL);
                path_dhcpd_pid = s;
        }
 
@@ -853,137 +850,116 @@ void postconf_initialization (int quiet)
                 oc = lookup_option(&server_universe, options,
                                    SV_DHCPV6_LEASE_FILE_NAME);
                 if (oc &&
-                    evaluate_option_cache(&db, NULL, NULL, NULL,
-                                         options, NULL, &global_scope,
-                                          oc, MDL)) {
-                        s = dmalloc (db.len + 1, MDL);
+                    evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                         &global_scope, oc, MDL)) {
+                        s = dmalloc(db.len + 1, MDL);
                         if (!s)
-                                log_fatal ("no memory for lease db filename.");
-                        memcpy (s, db.data, db.len);
-                        s [db.len] = 0;
-                        data_string_forget (&db, MDL);
+                                log_fatal("no memory for lease db filename.");
+                        memcpy(s, db.data, db.len);
+                        s[db.len] = 0;
+                        data_string_forget(&db, MDL);
                         path_dhcpd_db = s;
                 }
 
                 oc = lookup_option(&server_universe, options,
                                    SV_DHCPV6_PID_FILE_NAME);
                 if (oc &&
-                    evaluate_option_cache(&db, NULL, NULL, NULL,
-                                         options, NULL, &global_scope,
-                                          oc, MDL)) {
-                        s = dmalloc (db.len + 1, MDL);
+                    evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                         &global_scope, oc, MDL)) {
+                        s = dmalloc(db.len + 1, MDL);
                         if (!s)
-                                log_fatal ("no memory for pid filename.");
-                        memcpy (s, db.data, db.len);
-                        s [db.len] = 0;
-                        data_string_forget (&db, MDL);
+                                log_fatal("no memory for pid filename.");
+                        memcpy(s, db.data, db.len);
+                        s[db.len] = 0;
+                        data_string_forget(&db, MDL);
                         path_dhcpd_pid = s;
                 }
         }
 #endif /* DHCPv6 */
 
        omapi_port = -1;
-       oc = lookup_option (&server_universe, options, SV_OMAPI_PORT);
+       oc = lookup_option(&server_universe, options, SV_OMAPI_PORT);
        if (oc &&
-           evaluate_option_cache (&db, (struct packet *)0,
-                                  (struct lease *)0, (struct client_state *)0,
-                                  options, (struct option_state *)0,
-                                  &global_scope, oc, MDL)) {
+           evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                 &global_scope, oc, MDL)) {
                if (db.len == 2) {
-                       omapi_port = getUShort (db.data);
+                       omapi_port = getUShort(db.data);
                } else
-                       log_fatal ("invalid omapi port data length");
-               data_string_forget (&db, MDL);
+                       log_fatal("invalid omapi port data length");
+               data_string_forget(&db, MDL);
        }
 
-       oc = lookup_option (&server_universe, options, SV_OMAPI_KEY);
+       oc = lookup_option(&server_universe, options, SV_OMAPI_KEY);
        if (oc &&
-           evaluate_option_cache (&db, (struct packet *)0,
-                                  (struct lease *)0, (struct client_state *)0,
-                                  options,
-                                  (struct option_state *)0,
-                                  &global_scope, oc, MDL)) {
-               s = dmalloc (db.len + 1, MDL);
+           evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                 &global_scope, oc, MDL)) {
+               s = dmalloc(db.len + 1, MDL);
                if (!s)
-                       log_fatal ("no memory for OMAPI key filename.");
-               memcpy (s, db.data, db.len);
-               s [db.len] = 0;
-               data_string_forget (&db, MDL);
-               result = omapi_auth_key_lookup_name (&omapi_key, s);
-               dfree (s, MDL);
+                       log_fatal("no memory for OMAPI key filename.");
+               memcpy(s, db.data, db.len);
+               s[db.len] = 0;
+               data_string_forget(&db, MDL);
+               result = omapi_auth_key_lookup_name(&omapi_key, s);
+               dfree(s, MDL);
                if (result != ISC_R_SUCCESS)
-                       log_fatal ("OMAPI key %s: %s",
-                                  s, isc_result_totext (result));
+                       log_fatal("OMAPI key %s: %s",
+                                 s, isc_result_totext (result));
        }
 
-       oc = lookup_option (&server_universe, options, SV_LOCAL_PORT);
+       oc = lookup_option(&server_universe, options, SV_LOCAL_PORT);
        if (oc &&
-           evaluate_option_cache (&db, (struct packet *)0,
-                                  (struct lease *)0, (struct client_state *)0,
-                                  options,
-                                  (struct option_state *)0,
-                                  &global_scope, oc, MDL)) {
+           evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                 &global_scope, oc, MDL)) {
                if (db.len == 2) {
-                       local_port = htons (getUShort (db.data));
+                       local_port = htons(getUShort (db.data));
                } else
-                       log_fatal ("invalid local port data length");
-               data_string_forget (&db, MDL);
+                       log_fatal("invalid local port data length");
+               data_string_forget(&db, MDL);
        }
 
-       oc = lookup_option (&server_universe, options, SV_REMOTE_PORT);
+       oc = lookup_option(&server_universe, options, SV_REMOTE_PORT);
        if (oc &&
-           evaluate_option_cache (&db, (struct packet *)0,
-                                  (struct lease *)0, (struct client_state *)0,
-                                  options, (struct option_state *)0,
-                                  &global_scope, oc, MDL)) {
+           evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                 &global_scope, oc, MDL)) {
                if (db.len == 2) {
-                       remote_port = htons (getUShort (db.data));
+                       remote_port = htons(getUShort (db.data));
                } else
-                       log_fatal ("invalid remote port data length");
-               data_string_forget (&db, MDL);
+                       log_fatal("invalid remote port data length");
+               data_string_forget(&db, MDL);
        }
 
-       oc = lookup_option (&server_universe, options,
-                           SV_LIMITED_BROADCAST_ADDRESS);
+       oc = lookup_option(&server_universe, options,
+                          SV_LIMITED_BROADCAST_ADDRESS);
        if (oc &&
-           evaluate_option_cache (&db, (struct packet *)0,
-                                  (struct lease *)0, (struct client_state *)0,
-                                  options, (struct option_state *)0,
-                                  &global_scope, oc, MDL)) {
+           evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                 &global_scope, oc, MDL)) {
                if (db.len == 4) {
-                       memcpy (&limited_broadcast, db.data, 4);
+                       memcpy(&limited_broadcast, db.data, 4);
                } else
-                       log_fatal ("invalid broadcast address data length");
-               data_string_forget (&db, MDL);
+                       log_fatal("invalid broadcast address data length");
+               data_string_forget(&db, MDL);
        }
 
-       oc = lookup_option (&server_universe, options,
-                           SV_LOCAL_ADDRESS);
+       oc = lookup_option(&server_universe, options, SV_LOCAL_ADDRESS);
        if (oc &&
-           evaluate_option_cache (&db, (struct packet *)0,
-                                  (struct lease *)0, (struct client_state *)0,
-                                  options, (struct option_state *)0,
-                                  &global_scope, oc, MDL)) {
+           evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                 &global_scope, oc, MDL)) {
                if (db.len == 4) {
-                       memcpy (&local_address, db.data, 4);
+                       memcpy(&local_address, db.data, 4);
                } else
-                       log_fatal ("invalid local address data length");
-               data_string_forget (&db, MDL);
+                       log_fatal("invalid local address data length");
+               data_string_forget(&db, MDL);
        }
 
-       oc = lookup_option (&server_universe, options, SV_DDNS_UPDATE_STYLE);
+       oc = lookup_option(&server_universe, options, SV_DDNS_UPDATE_STYLE);
        if (oc) {
-               if (evaluate_option_cache (&db, (struct packet *)0,
-                                          (struct lease *)0,
-                                          (struct client_state *)0,
-                                          options,
-                                          (struct option_state *)0,
-                                          &global_scope, oc, MDL)) {
+               if (evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                         &global_scope, oc, MDL)) {
                        if (db.len == 1) {
-                               ddns_update_style = db.data [0];
+                               ddns_update_style = db.data[0];
                        } else
-                               log_fatal ("invalid dns update type");
-                       data_string_forget (&db, MDL);
+                               log_fatal("invalid dns update type");
+                       data_string_forget(&db, MDL);
                }
        } else {
                ddns_update_style = DDNS_UPDATE_STYLE_NONE;
@@ -1000,17 +976,13 @@ void postconf_initialization (int quiet)
        }
 #endif
 
-       oc = lookup_option (&server_universe, options, SV_LOG_FACILITY);
+       oc = lookup_option(&server_universe, options, SV_LOG_FACILITY);
        if (oc) {
-               if (evaluate_option_cache (&db, (struct packet *)0,
-                                          (struct lease *)0,
-                                          (struct client_state *)0,
-                                          options,
-                                          (struct option_state *)0,
-                                          &global_scope, oc, MDL)) {
+               if (evaluate_option_cache(&db, NULL, NULL, NULL, options, NULL,
+                                         &global_scope, oc, MDL)) {
                        if (db.len == 1) {
                                closelog ();
-                               openlog ("dhcpd", LOG_NDELAY, db.data[0]);
+                               openlog("dhcpd", LOG_NDELAY, db.data[0]);
                                /* Log the startup banner into the new
                                   log file. */
                                if (!quiet) {
@@ -1019,14 +991,14 @@ void postconf_initialization (int quiet)
                                        log_perror = 0;
                                        log_info("%s %s",
                                                 message, PACKAGE_VERSION);
-                                       log_info (copyright);
-                                       log_info (arr);
-                                       log_info (url);
+                                       log_info(copyright);
+                                       log_info(arr);
+                                       log_info(url);
                                        log_perror = tmp;
                                }
                        } else
-                               log_fatal ("invalid log facility");
-                       data_string_forget (&db, MDL);
+                               log_fatal("invalid log facility");
+                       data_string_forget(&db, MDL);
                }
        }
        
@@ -1058,8 +1030,16 @@ void postconf_initialization (int quiet)
                data_string_forget(&db, MDL);
        }
 
+       oc = lookup_option(&server_universe, options, SV_DONT_USE_FSYNC);
+       if ((oc != NULL) &&
+           evaluate_boolean_option_cache(NULL, NULL, NULL, NULL, options, NULL,
+                                         &global_scope, oc, MDL)) {
+               dont_use_fsync = 1;
+               log_error("Not using fsync() to flush lease writes");
+       }
+
        /* Don't need the options anymore. */
-       option_state_dereference (&options, MDL);
+       option_state_dereference(&options, MDL);
 }
 
 void postdb_startup (void)

diff --git a/server/dhcpd.conf.5 b/server/dhcpd.conf.5
index f842f33765965480d3c9ed8f75e6d9e503dd4f35..8a132b8d3580905abf515853f605be3abacaea67 100644 (file)
--- a/server/dhcpd.conf.5
+++ b/server/dhcpd.conf.5
@@ -2110,6 +2110,24 @@ will still honor the setting of the \fBclient-updates\fR flag.
 .RE
 .PP
 The
+.I dont-use-async
+statement
+.RS 0.25i
+.PP
+.B dont-use-async \fIflag\fB;\fR
+.PP
+The \fIdont-use-async\fR statement instructs the DHCP server if
+it should call fsync() when writing leases to the lease file.  By
+default and if the flag is set to false the server \fBwill\fR call
+fsync().  Suppressing the call to fsync() may increase the performance
+of the server but it also adds a risk that a lease will not be
+properly written to the disk after it has been issued to a client
+and before the server stops.  This can lead to duplicate leases
+being issued to different clients.  Using this option is \fBnot
+recommended\FR.
+.RE
+.PP
+The
 .I dynamic-bootp-lease-cutoff
 statement
 .RS 0.25i

diff --git a/server/stables.c b/server/stables.c
index 36335c76cfded7191e6b977b4a13337563b1c7fe..37758cc15d0a4ad2ea89d0713020a023347ff930 100644 (file)
--- a/server/stables.c
+++ b/server/stables.c
@@ -267,6 +267,7 @@ static struct option server_options[] = {
 #endif /* LDAP_USE_SSL */
 #endif /* LDAP_CONFIGURATION */
        { "dhcp-cache-threshold", "B",          &server_universe,  78, 1 },
+       { "dont-use-fsync", "f",                &server_universe,  79, 1 },
        { NULL, NULL, NULL, 0, 0 }
 };