Milter-greylist

Emmanuel Dreyfus <manu@...> wrote:

> A simple way of fixing the issue would just be to issue a TEMPFAIL in
> this situation, which would reflect the real problem: your system cannot
> function proprely because of resource exhaustion, and the sender should
> retry later.

Wait, wait, wait... fopen/fdopen usage is quite limited:
1) dump.c, for duming the database
2) sync.c, for MX sync
3) milter-greylist.c, for the PID file
4) stat.c, for the custom stat output

#3 and #4 are not a problem: it happens on startup and you'll never use
a file descriptor above 256 here

#2 can happen if the MX sync connection breaks during operation
#1 is what Solaris users experience

The TEMPFAIL solution won't help here, but we can make sure we keep a
file descriptor < 256 open for dumps: after a dumps succeeds, we open
/dev/null and use dup2 to associate it to the low file descriptor we
just used. On the next dump, we open the new file, use dup2 and here we
are. I quickly wrote some code for that idea just below (not tested, not
built)

Opinions?

diff -U2 -r1.32 dump.c
--- dump.c      27 Sep 2007 03:47:25 -0000      1.32
+++ dump.c      27 Sep 2007 03:35:02 -0000
@@ -202,6 +202,7 @@
        int final;
 {
+       static int dumpfd = -1;
+       int newdumpfd;
        FILE *dump;
-       int dumpfd;
        struct timeval tv1, tv2, tv3;
        char newdumpfile[MAXPATHLEN + 1];
@@ -234,4 +235,12 @@
        }
 
+       if (dumpfd == -1) {
+               if ((dumpfd = open(_PATH_DEVNULL, O_RDONLY, 0)) == -1) {
+                       mg_log(LOG_ERR, "cannot open \"%s\", 
+                           _PATH_DEVNULL, strerror(errno));
+                       exit(EX_OSERR);
+               }
+       }
+               
        /* 
         * Dump the database in a temporary file and 
@@ -244,12 +253,14 @@
            "%s-XXXXXXXX", conf.c_dumpfile);
 
-       if ((dumpfd = mkstemp(newdumpfile)) == -1) {
+       if ((newdumpfd = mkstemp(newdumpfile)) == -1) {
                mg_log(LOG_ERR, "mkstemp(\"%s\") failed: %s", 
                    newdumpfile, strerror(errno));
-               close(dumpfd);
+               close(newdumpfd);
                unlink(newdumpfile);            /* clean up ... */
                exit(EX_OSERR);
        }
 
+       dumpfd = dup2(newdumpfd, dumpfd);
+
        errno = 0;
        if ((dump = fdopen(dumpfd, "w")) == NULL) {
@@ -278,4 +289,10 @@
            "whitelisted\n#\n", done, greylisted_count,
whitelisted_count);
 
+       fflush(dump);
+       if ((dumpfd = open(_PATH_DEVNULL, O_RDONLY, 0)) == -1) {
+               mg_log(LOG_ERR, "cannot open \"%s\", 
+                   _PATH_DEVNULL, strerror(errno));
+               exit(EX_OSERR);
+       }
        fclose(dump);
        if (s_buffer)


-- 
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu@...