support/export/xtab.c

   1 /*
   2  * support/export/xtab.c
   3  *
   4  * Interface to the xtab file.
   5  *
   6  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
   7  */
   8
   9 #ifdef HAVE_CONFIG_H
  10 #include <config.h>
  11 #endif
  12
  13 #include <sys/fcntl.h>
  14 #include <unistd.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include "xmalloc.h"
  18 #include "nfslib.h"
  19 #include "exportfs.h"
  20 #include "xio.h"
  21 #include "xlog.h"
  22
  23 static void cond_rename(char *newfile, char *oldfile);
  24
  25 static int
  26 xtab_read(char *xtab, char *lockfn, int is_export)
  27 {
  28     /* is_export == 0  => reading /proc/fs/nfs/exports - we know these things are exported to kernel
  29      * is_export == 1  => reading /var/lib/nfs/etab - these things are allowed to be exported
  30      * is_export == 2  => reading /var/lib/nfs/xtab - these things might be known to kernel
  31      */
  32         struct exportent        *xp;
  33         nfs_export              *exp;
  34         int                     lockid;
  35
  36         if ((lockid = xflock(lockfn, "r")) < 0)
  37                 return 0;
  38         setexportent(xtab, "r");
  39         while ((xp = getexportent(is_export==0, 0)) != NULL) {
  40                 if (!(exp = export_lookup(xp->e_hostname, xp->e_path, is_export != 1)) &&
  41                     !(exp = export_create(xp, is_export!=1))) {
  42                         continue;
  43                 }
  44                 switch (is_export) {
  45                 case 0:
  46                         exp->m_exported = 1;
  47                         break;
  48                 case 1:
  49                         exp->m_xtabent = 1;
  50                         exp->m_mayexport = 1;
  51                         break;
  52                 case 2:
  53                         exp->m_exported = -1;/* may be exported */
  54                         break;
  55                 }
  56         }
  57         endexportent();
  58         xfunlock(lockid);
  59
  60         return 0;
  61 }
  62
  63 int
  64 xtab_mount_read(void)
  65 {
  66         int fd;
  67         if ((fd=open(_PATH_PROC_EXPORTS, O_RDONLY))>=0) {
  68                 close(fd);
  69                 return xtab_read(_PATH_PROC_EXPORTS,
  70                                  _PATH_PROC_EXPORTS, 0);
  71         } else if ((fd=open(_PATH_PROC_EXPORTS_ALT, O_RDONLY) >= 0)) {
  72                 close(fd);
  73                 return xtab_read(_PATH_PROC_EXPORTS_ALT,
  74                                  _PATH_PROC_EXPORTS_ALT, 0);
  75         } else
  76                 return xtab_read(_PATH_XTAB, _PATH_XTABLCK, 2);
  77 }
  78
  79 int
  80 xtab_export_read(void)
  81 {
  82         return xtab_read(_PATH_ETAB, _PATH_ETABLCK, 1);
  83 }
  84
  85 /*
  86  * mountd now keeps an open fd for the etab at all times to make sure that the
  87  * inode number changes when the xtab_export_write is done. If you change the
  88  * routine below such that the files are edited in place, then you'll need to
  89  * fix the auth_reload logic as well...
  90  */
  91 static int
  92 xtab_write(char *xtab, char *xtabtmp, char *lockfn, int is_export)
  93 {
  94         struct exportent        xe;
  95         nfs_export              *exp;
  96         int                     lockid, i;
  97
  98         if ((lockid = xflock(lockfn, "w")) < 0) {
  99                 xlog(L_ERROR, "can't lock %s for writing", xtab);
 100                 return 0;
 101         }
 102         setexportent(xtabtmp, "w");
 103
 104         for (i = 0; i < MCL_MAXTYPES; i++) {
 105                 for (exp = exportlist[i].p_head; exp; exp = exp->m_next) {
 106                         if (is_export && !exp->m_xtabent)
 107                                 continue;
 108                         if (!is_export && ! exp->m_exported)
 109                                 continue;
 110
 111                         /* write out the export entry using the FQDN */
 112                         xe = exp->m_export;
 113                         xe.e_hostname = exp->m_client->m_hostname;
 114                         putexportent(&xe);
 115                 }
 116         }
 117         endexportent();
 118
 119         cond_rename(xtabtmp, xtab);
 120
 121         xfunlock(lockid);
 122
 123         return 1;
 124 }
 125
 126 int
 127 xtab_export_write()
 128 {
 129         return xtab_write(_PATH_ETAB, _PATH_ETABTMP, _PATH_ETABLCK, 1);
 130 }
 131
 132 int
 133 xtab_mount_write()
 134 {
 135         return xtab_write(_PATH_XTAB, _PATH_XTABTMP, _PATH_XTABLCK, 0);
 136 }
 137
 138 void
 139 xtab_append(nfs_export *exp)
 140 {
 141         struct exportent xe;
 142         int             lockid;
 143
 144         if ((lockid = xflock(_PATH_XTABLCK, "w")) < 0)
 145                 return;
 146         setexportent(_PATH_XTAB, "a");
 147         xe = exp->m_export;
 148         xe.e_hostname = exp->m_client->m_hostname;
 149         putexportent(&xe);
 150         endexportent();
 151         xfunlock(lockid);
 152         exp->m_xtabent = 1;
 153 }
 154
 155 /*
 156  * rename newfile onto oldfile unless
 157  * they are identical
 158  */
 159 static void cond_rename(char *newfile, char *oldfile)
 160 {
 161         int nfd, ofd;
 162         char nbuf[4096], obuf[4096];
 163         int ncnt, ocnt;
 164
 165         nfd = open(newfile, 0);
 166         if (nfd < 0)
 167                 return;
 168         ofd = open(oldfile, 0);
 169         if (ofd < 0) {
 170                 close(nfd);
 171                 rename(newfile, oldfile);
 172                 return;
 173         }
 174
 175         do {
 176                 ncnt = read(nfd, nbuf, sizeof(nbuf));
 177                 if (ncnt < 0)
 178                         break;
 179                 ocnt = read(ofd, obuf, sizeof(obuf));
 180                 if (ocnt < 0)
 181                         break;
 182                 if (ncnt != ocnt)
 183                         break;
 184                 if (ncnt == 0) {
 185                         close(nfd);
 186                         close(ofd);
 187                         unlink(newfile);
 188                         return;
 189                 }
 190         } while (memcmp(obuf, nbuf, ncnt) == 0);
 191
 192         /* some mis-match */
 193         close(nfd);
 194         close(ofd);
 195         rename(newfile, oldfile);
 196         return;
 197 }