bindresvport(3)

1BINDRESVPORT(3)            Linux Programmer's Manual           BINDRESVPORT(3)
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NAME

6       bindresvport - bind a socket to a privileged IP port
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SYNOPSIS

9       #include <sys/types.h>
10       #include <netinet/in.h>
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12       int bindresvport(int sockfd, struct sockaddr_in *sin);
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DESCRIPTION

15       bindresvport()  is  used to bind the socket referred to by the file de‐
16       scriptor sockfd to a privileged anonymous IP port, that is, a port num‐
17       ber arbitrarily selected from the range 512 to 1023.
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19       If  the  bind(2)  performed by bindresvport() is successful, and sin is
20       not NULL, then sin->sin_port returns the  port  number  actually  allo‐
21       cated.
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23       sin  can  be NULL, in which case sin->sin_family is implicitly taken to
24       be AF_INET.  However, in this case, bindresvport() has no way to return
25       the port number actually allocated.  (This information can later be ob‐
26       tained using getsockname(2).)
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RETURN VALUE

29       bindresvport() returns 0 on success; otherwise -1 is returned and errno
30       is set to indicate the error.
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ERRORS

33       bindresvport() can fail for any of the same reasons as bind(2).  In ad‐
34       dition, the following errors may occur:
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36       EACCES The calling process was not privileged (on  Linux:  the  calling
37              process  did not have the CAP_NET_BIND_SERVICE capability in the
38              user namespace governing its network namespace).
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40       EADDRINUSE
41              All privileged ports are in use.
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43       EAFNOSUPPORT (EPFNOSUPPORT in glibc 2.7 and earlier)
44              sin is not NULL and sin->sin_family is not AF_INET.
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ATTRIBUTES

47       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
48       tributes(7).
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50       ┌───────────────┬───────────────┬──────────────────────────────────────┐
51       │Interface      │ Attribute     │ Value                                │
52       ├───────────────┼───────────────┼──────────────────────────────────────┤
53       │bindresvport() │ Thread safety │ glibc >= 2.17: MT-Safe;              │
54       │               │               │ glibc < 2.17: MT-Unsafe              │
55       └───────────────┴───────────────┴──────────────────────────────────────┘
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57       The bindresvport() function uses a static variable that  was  not  pro‐
58       tected by a lock before glibc 2.17, rendering the function MT-Unsafe.
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CONFORMING TO

61       Not in POSIX.1.  Present on the BSDs, Solaris, and many other systems.
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NOTES

64       Unlike  some  bindresvport()  implementations, the glibc implementation
65       ignores any value that the caller supplies in sin->sin_port.
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COLOPHON

71       This page is part of release 5.12 of the Linux  man-pages  project.   A
72       description  of  the project, information about reporting bugs, and the
73       latest    version    of    this    page,    can     be     found     at
74       https://www.kernel.org/doc/man-pages/.
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78                                  2021-03-22                   BINDRESVPORT(3)