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1 /*
2  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #include <sys/types.h>
12 #include <dirent.h>
13 #include <errno.h>
14 #include <stdlib.h>
15 #include <string.h>
16 
17 #include "webrtc/base/linuxfdwalk.h"
18 
19 // Parses a file descriptor number in base 10, requiring the strict format used
20 // in /proc/*/fd. Returns the value, or -1 if not a valid string.
parse_fd(const char * s)21 static int parse_fd(const char *s) {
22   if (!*s) {
23     // Empty string is invalid.
24     return -1;
25   }
26   int val = 0;
27   do {
28     if (*s < '0' || *s > '9') {
29       // Non-numeric characters anywhere are invalid.
30       return -1;
31     }
32     int digit = *s++ - '0';
33     val = val * 10 + digit;
34   } while (*s);
35   return val;
36 }
37 
fdwalk(void (* func)(void *,int),void * opaque)38 int fdwalk(void (*func)(void *, int), void *opaque) {
39   DIR *dir = opendir("/proc/self/fd");
40   if (!dir) {
41     return -1;
42   }
43   int opendirfd = dirfd(dir);
44   int parse_errors = 0;
45   struct dirent *ent;
46   // Have to clear errno to distinguish readdir() completion from failure.
47   while (errno = 0, (ent = readdir(dir)) != NULL) {
48     if (strcmp(ent->d_name, ".") == 0 ||
49         strcmp(ent->d_name, "..") == 0) {
50       continue;
51     }
52     // We avoid atoi or strtol because those are part of libc and they involve
53     // locale stuff, which is probably not safe from a post-fork context in a
54     // multi-threaded app.
55     int fd = parse_fd(ent->d_name);
56     if (fd < 0) {
57       parse_errors = 1;
58       continue;
59     }
60     if (fd != opendirfd) {
61       (*func)(opaque, fd);
62     }
63   }
64   int saved_errno = errno;
65   if (closedir(dir) < 0) {
66     if (!saved_errno) {
67       // Return the closedir error.
68       return -1;
69     }
70     // Else ignore it because we have a more relevant error to return.
71   }
72   if (saved_errno) {
73     errno = saved_errno;
74     return -1;
75   } else if (parse_errors) {
76     errno = EBADF;
77     return -1;
78   } else {
79     return 0;
80   }
81 }
82