diplodocus.org Git - mdeliver/blob - mdeliver.c

   1 /* mdeliver.c -- Deliver a message to a Maildir.
   2  *
   3  * $Id$
   4  *
   5  * This program is in the public domain.
   6  */
   7
   8 #include <sys/types.h>
   9 #include <sys/stat.h>
  10
  11 #include <err.h>
  12 #include <errno.h>
  13 #include <fcntl.h>
  14 #include <limits.h>
  15 #include <stdio.h>
  16 #include <stdlib.h>
  17 #include <string.h>
  18 #include <sysexits.h>
  19 #include <time.h>
  20 #include <unistd.h>
  21
  22 #if !defined(HOST_NAME_MAX)
  23 #if defined MAXHOSTNAMELEN
  24 #define HOST_NAME_MAX MAXHOSTNAMELEN
  25 #else
  26 #define HOST_NAME_MAX 64
  27 #endif
  28 #endif
  29
  30 /* holds 2^128 - 1 in decimal, plus '\0' */
  31 #define LEN_ULONG 40
  32
  33 /* 1 for '\0', 4 for "tmp/", HOST_NAME_MAX for the hostname, and two
  34  * LEN_ULONGs for time and pid. */
  35 #define TMPNAMLEN 1 + 4 + HOST_NAME_MAX + LEN_ULONG + LEN_ULONG
  36
  37 /* Write all of buf, even if write(2) is interrupted. */
  38 static ssize_t
  39 full_write(int fd, const char *buf, size_t nbytes)
  40 {
  41     ssize_t r, w = 0;
  42
  43     /* Loop until nbytes of buf have been written. */
  44     while (w < nbytes) {
  45         /* Keep trying until write succeeds without interruption. */
  46         do {
  47             r = write(fd, buf + w, nbytes - w);
  48         } while (r < 0 && errno == EINTR);
  49
  50         if (r < 0) {
  51             return r;
  52         }
  53
  54         w += r;
  55     }
  56
  57     return w;
  58 }
  59
  60 static void
  61 deliver(char *maildir, char *newfn)
  62 {
  63     char fn[TMPNAMLEN], host[HOST_NAME_MAX + 1];
  64     char *buildfn;              /* used to build up the fn */
  65     time_t now;
  66     struct tm *t;
  67     pid_t pid;
  68     struct stat statbuf;
  69     int try;
  70     int fd, r;
  71     char buf[BUFSIZ];
  72
  73     if (chdir(maildir) != 0) {
  74         err(EX_TEMPFAIL, "Failed chdir(%s)", maildir);
  75     }
  76
  77     pid = getpid();
  78     gethostname(host, sizeof(host));
  79
  80     for (try = 0; ; try++) {
  81         now = time(NULL);
  82         t = gmtime(&now);
  83
  84         buildfn = fn + sprintf(fn, "tmp/");
  85         buildfn += strftime(buildfn, LEN_ULONG + 1, "%s.", t);
  86         buildfn += snprintf(buildfn, LEN_ULONG + 1, "%d.", pid);
  87         buildfn += sprintf(buildfn, "%s", host);
  88
  89         if (stat(fn, &statbuf) != 0) {
  90             if (errno == ENOENT) {
  91                 break;
  92             }
  93         }
  94
  95         if (try == 2) {
  96             errx(EX_TEMPFAIL, "Attempted filename exists.");
  97         }
  98
  99         sleep(2);
 100     }
 101
 102     fd = open(fn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 103     if (fd < 0) {
 104         err(EX_TEMPFAIL, "Failed open(%s)", fn);
 105     }
 106
 107     /* From this point, we have a tmp file, so if someting fails we
 108      * must try to unlink it before bombing. */
 109
 110     while ((r = read(STDIN_FILENO, buf, BUFSIZ)) > 0) {
 111         if (full_write(fd, buf, r) != r) {
 112             unlink(fn);
 113             err(EX_TEMPFAIL, "Failed write(%s)", fn);
 114         }
 115     }
 116
 117     if (fsync(fd) < 0) {
 118         unlink(fn);
 119         err(EX_TEMPFAIL, "Failed fsync(%s)", fn);
 120     }
 121     if (close(fd) < 0) {
 122         unlink(fn);
 123         err(EX_TEMPFAIL, "Failed close(%s)", fn);
 124     }
 125
 126     strcpy(newfn, fn);
 127     memcpy(newfn, "new", 3);
 128
 129     if (rename(fn, newfn) != 0) {
 130         unlink(fn);
 131         err(EX_TEMPFAIL, "Failed rename(%s, new)", fn);
 132     }
 133 }
 134
 135 int
 136 main(int argc, char *argv[])
 137 {
 138     char newfn[TMPNAMLEN];
 139     pid_t pid;
 140     FILE *errfile;
 141     char *fail;
 142     int fd;
 143
 144     deliver("Maildir", newfn);
 145
 146     if (argv[1]) {
 147         if ((pid = fork()) > 0) {
 148             return 0;
 149         } else if (pid == 0) {
 150             argv[0] = argv[1];
 151             argv[1] = newfn;
 152             execvp(argv[0], argv);
 153             fail = "exec";
 154         } else {
 155             fail = "fork";
 156         }
 157
 158         /* If we got here fork or exec failed, so try to write an
 159          * error message where later mail processors can find it.  We
 160          * really can't do anything about it if this fails. */
 161         memcpy(newfn, "err", 3);
 162         fd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 163         errfile = fdopen(fd, "w");
 164         if (errfile) {
 165             fprintf(errfile, "%s:%d\n", fail, errno);
 166         }
 167     }
 168
 169     /* Always return 0 because deliver exits if it fails, and if it
 170      * succeeds we cannot return a failure code to the MTA. */
 171     return 0;
 172 }