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      1 /*
      2  * libjingle
      3  * Copyright 2004--2009, Google Inc.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are met:
      7  *
      8  *  1. Redistributions of source code must retain the above copyright notice,
      9  *     this list of conditions and the following disclaimer.
     10  *  2. Redistributions in binary form must reproduce the above copyright notice,
     11  *     this list of conditions and the following disclaimer in the documentation
     12  *     and/or other materials provided with the distribution.
     13  *  3. The name of the author may not be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 #include <sys/types.h>
     29 #include <dirent.h>
     30 #include <errno.h>
     31 #include <stdlib.h>
     32 #include <string.h>
     33 
     34 #include "talk/base/linuxfdwalk.h"
     35 
     36 // Parses a file descriptor number in base 10, requiring the strict format used
     37 // in /proc/*/fd. Returns the value, or -1 if not a valid string.
     38 static int parse_fd(const char *s) {
     39   if (!*s) {
     40     // Empty string is invalid.
     41     return -1;
     42   }
     43   int val = 0;
     44   do {
     45     if (*s < '0' || *s > '9') {
     46       // Non-numeric characters anywhere are invalid.
     47       return -1;
     48     }
     49     int digit = *s++ - '0';
     50     val = val * 10 + digit;
     51   } while (*s);
     52   return val;
     53 }
     54 
     55 int fdwalk(void (*func)(void *, int), void *opaque) {
     56   DIR *dir = opendir("/proc/self/fd");
     57   if (!dir) {
     58     return -1;
     59   }
     60   int opendirfd = dirfd(dir);
     61   int parse_errors = 0;
     62   struct dirent *ent;
     63   // Have to clear errno to distinguish readdir() completion from failure.
     64   while (errno = 0, (ent = readdir(dir)) != NULL) {
     65     if (strcmp(ent->d_name, ".") == 0 ||
     66         strcmp(ent->d_name, "..") == 0) {
     67       continue;
     68     }
     69     // We avoid atoi or strtol because those are part of libc and they involve
     70     // locale stuff, which is probably not safe from a post-fork context in a
     71     // multi-threaded app.
     72     int fd = parse_fd(ent->d_name);
     73     if (fd < 0) {
     74       parse_errors = 1;
     75       continue;
     76     }
     77     if (fd != opendirfd) {
     78       (*func)(opaque, fd);
     79     }
     80   }
     81   int saved_errno = errno;
     82   if (closedir(dir) < 0) {
     83     if (!saved_errno) {
     84       // Return the closedir error.
     85       return -1;
     86     }
     87     // Else ignore it because we have a more relevant error to return.
     88   }
     89   if (saved_errno) {
     90     errno = saved_errno;
     91     return -1;
     92   } else if (parse_errors) {
     93     errno = EBADF;
     94     return -1;
     95   } else {
     96     return 0;
     97   }
     98 }
     99