improved locking to avoid errors during alias rebuild

SCCS-vsn: usr.sbin/sendmail/src/map.c 6.24

diff --git a/usr/src/usr.sbin/sendmail/src/map.c b/usr/src/usr.sbin/sendmail/src/map.c
index 8bb8677..015fc18 100644 (file)
--- a/usr/src/usr.sbin/sendmail/src/map.c
+++ b/usr/src/usr.sbin/sendmail/src/map.c
@@ -7,7 +7,7 @@
  */
 
 #ifndef lint
  */
 
 #ifndef lint

-static char sccsid[] = "@(#)map.c      6.23 (Berkeley) %G%";
+static char sccsid[] = "@(#)map.c      6.24 (Berkeley) %G%";

 #endif /* not lint */
 
 #include "sendmail.h"
 #endif /* not lint */
 
 #include "sendmail.h"


@@ -498,13 +498,21 @@ ndbm_map_close(map)
 
 #endif
 \f/*
 
 #endif
 \f/*

-**  HASH (NEWDB) Modules
+**  NEWDB (Hash and BTree) Modules

 */
 
 #ifdef NEWDB
 
 /*
 */
 
 #ifdef NEWDB
 
 /*

-**  BTREE_MAP_PARSE -- BTREE-style map initialization
+**  BT_MAP_OPEN, HASH_MAP_OPEN -- database open primitives.
+**
+**     These do rather bizarre locking.  If you can lock on open,
+**     do that to avoid the condition of opening a database that
+**     is being rebuilt.  If you don't, we'll try to fake it, but
+**     there will be a race condition.  If opening for read-only,
+**     we immediately release the lock to avoid freezing things up.
+**     We really ought to hold the lock, but guarantee that we won't
+**     be pokey about it.  That's hard to do.

 */
 
 bool
 */
 
 bool


@@ -514,25 +522,47 @@ bt_map_open(map, mode)
 {
        DB *db;
        int i;
 {
        DB *db;
        int i;

+       int omode;

        char buf[MAXNAME];
 
        if (tTd(38, 2))
                printf("bt_map_open(%s, %d)\n", map->map_file, mode);
 
        char buf[MAXNAME];
 
        if (tTd(38, 2))
                printf("bt_map_open(%s, %d)\n", map->map_file, mode);
 

-       if (mode == O_RDWR)
-               mode |= O_CREAT|O_TRUNC;
+       omode = mode;
+       if (omode == O_RDWR)
+       {
+               omode |= O_CREAT|O_TRUNC;
+#if defined(O_EXLOCK) && !defined(LOCKF)
+               omode |= O_EXLOCK;
+# if !defined(OLD_NEWDB)
+       }
+       else
+       {
+               omode |= O_SHLOCK;
+# endif
+#endif
+       }

 
        (void) strcpy(buf, map->map_file);
        i = strlen(buf);
        if (i < 3 || strcmp(&buf[i - 3], ".db") != 0)
                (void) strcat(buf, ".db");
 
        (void) strcpy(buf, map->map_file);
        i = strlen(buf);
        if (i < 3 || strcmp(&buf[i - 3], ".db") != 0)
                (void) strcat(buf, ".db");

-       db = dbopen(buf, mode, DBMMODE, DB_BTREE, NULL);
+       db = dbopen(buf, omode, DBMMODE, DB_BTREE, NULL);

        if (db == NULL)
        {
                if (!bitset(MF_OPTIONAL, map->map_mflags))
                        syserr("Cannot open BTREE database %s", map->map_file);
                return FALSE;
        }
        if (db == NULL)
        {
                if (!bitset(MF_OPTIONAL, map->map_mflags))
                        syserr("Cannot open BTREE database %s", map->map_file);
                return FALSE;
        }

+#if !defined(OLD_NEWDB) && !defined(LOCKF)
+# if !defined(O_EXLOCK)
+       if (mode == O_RDWR)
+               (void) lockfile(db->fd(db), map->map_file, LOCK_EX);
+# else
+       if (mode == O_RDONLY)
+               (void) lockfile(db->fd(db), map->map_file, LOCK_UN);
+# endif
+#endif

        map->map_db2 = (void *) db;
        if (mode == O_RDONLY && bitset(MF_ALIAS, map->map_mflags))
                aliaswait(map, ".db");
        map->map_db2 = (void *) db;
        if (mode == O_RDONLY && bitset(MF_ALIAS, map->map_mflags))
                aliaswait(map, ".db");


@@ -551,25 +581,47 @@ hash_map_open(map, mode)
 {
        DB *db;
        int i;
 {
        DB *db;
        int i;

+       int omode;

        char buf[MAXNAME];
 
        if (tTd(38, 2))
                printf("hash_map_open(%s, %d)\n", map->map_file, mode);
 
        char buf[MAXNAME];
 
        if (tTd(38, 2))
                printf("hash_map_open(%s, %d)\n", map->map_file, mode);
 

-       if (mode == O_RDWR)
-               mode |= O_CREAT|O_TRUNC;
+       omode = mode;
+       if (omode == O_RDWR)
+       {
+               omode |= O_CREAT|O_TRUNC;
+#if defined(O_EXLOCK) && !defined(LOCKF)
+               omode |= O_EXLOCK;
+# if !defined(OLD_NEWDB)
+       }
+       else
+       {
+               omode |= O_SHLOCK;
+# endif
+#endif
+       }

 
        (void) strcpy(buf, map->map_file);
        i = strlen(buf);
        if (i < 3 || strcmp(&buf[i - 3], ".db") != 0)
                (void) strcat(buf, ".db");
 
        (void) strcpy(buf, map->map_file);
        i = strlen(buf);
        if (i < 3 || strcmp(&buf[i - 3], ".db") != 0)
                (void) strcat(buf, ".db");

-       db = dbopen(buf, mode, DBMMODE, DB_HASH, NULL);
+       db = dbopen(buf, omode, DBMMODE, DB_HASH, NULL);

        if (db == NULL)
        {
                if (!bitset(MF_OPTIONAL, map->map_mflags))
                        syserr("Cannot open HASH database %s", map->map_file);
                return FALSE;
        }
        if (db == NULL)
        {
                if (!bitset(MF_OPTIONAL, map->map_mflags))
                        syserr("Cannot open HASH database %s", map->map_file);
                return FALSE;
        }

+#if !defined(OLD_NEWDB) && !defined(LOCKF)
+# if !defined(O_EXLOCK)
+       if (mode == O_RDWR)
+               (void) lockfile(db->fd(db), map->map_file, LOCK_EX);
+# else
+       if (mode == O_RDONLY)
+               (void) lockfile(db->fd(db), map->map_file, LOCK_UN);
+# endif
+#endif

        map->map_db2 = (void *) db;
        if (mode == O_RDONLY && bitset(MF_ALIAS, map->map_mflags))
                aliaswait(map, ".db");
        map->map_db2 = (void *) db;
        if (mode == O_RDONLY && bitset(MF_ALIAS, map->map_mflags))
                aliaswait(map, ".db");