1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2015 */
6 /* See the file NOTICE for conditions of use and distribution. */
8 /* Functions concerned with serialization. */
16 /*************************************************
17 * Test for host or ETRN serialization *
18 *************************************************/
20 /* This function is called when a host is listed for serialization of
21 connections. It is also called when ETRN is listed for serialization. We open
22 the misc database and look for a record, which implies an existing connection
23 or ETRN run. If increasing the count would take us past the given limit
24 value return FALSE. If not, bump it and return TRUE. If not found, create
25 one with value 1 and return TRUE.
28 key string on which to serialize
31 Returns: TRUE if OK to proceed; FALSE otherwise
36 enq_start(uschar *key, unsigned lim)
38 dbdata_serialize *serial_record;
39 dbdata_serialize new_record;
43 DEBUG(D_transport) debug_printf("check serialized: %s\n", key);
45 /* Open and lock the waiting information database. The absence of O_CREAT is
46 deliberate; the dbfn_open() function - which is an Exim function - always tries
47 to create if it can't open a read/write file. It expects only O_RDWR or
48 O_RDONLY as its argument. */
50 if (!(dbm_file = dbfn_open(US"misc", O_RDWR, &dbblock, TRUE, TRUE)))
53 /* See if there is a record for this host or queue run; if there is, we cannot
54 proceed with the connection unless the record is very old. */
56 serial_record = dbfn_read(dbm_file, key);
57 if (serial_record && time(NULL) - serial_record->time_stamp < 6*60*60)
59 if (serial_record->count >= lim)
62 DEBUG(D_transport) debug_printf("outstanding serialization record for %s\n",
66 new_record.count = serial_record->count + 1;
71 /* We can proceed - insert a new record or update the old one. */
73 DEBUG(D_transport) debug_printf("write serialization record for %s val %d\n",
74 key, new_record.count);
75 dbfn_write(dbm_file, key, &new_record, (int)sizeof(dbdata_serialize));
82 /*************************************************
83 * Release serialization *
84 *************************************************/
86 /* This function is called when a serialized host's connection or serialized
87 ETRN queue run ends. We open the relevant database and delete its record.
90 key the serialization key
100 dbdata_serialize *serial_record;
102 DEBUG(D_transport) debug_printf("end serialized: %s\n", key);
104 if ( !(dbm_file = dbfn_open(US"misc", O_RDWR, &dbblock, TRUE, TRUE))
105 || !(serial_record = dbfn_read(dbm_file, key))
108 if (--serial_record->count > 0)
110 DEBUG(D_transport) debug_printf("write serialization record for %s val %d\n",
111 key, serial_record->count);
112 dbfn_write(dbm_file, key, serial_record, (int)sizeof(dbdata_serialize));
116 DEBUG(D_transport) debug_printf("remove serialization record for %s\n", key);
117 dbfn_delete(dbm_file, key);
119 dbfn_close(dbm_file);