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
16       descriptor sockfd to a privileged anonymous IP port, that  is,  a  port
17       number 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
26       obtained using getsockname(2).)
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RETURN VALUE

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

33       bindresvport()  can  fail  for  any of the same reasons as bind(2).  In
34       addition, 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
48       attributes(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       └───────────────┴───────────────┴─────────────────────────┘
56       The  bindresvport()  function  uses a static variable that was not pro‐
57       tected by a lock before glibc 2.17, rendering the function MT-Unsafe.
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CONFORMING TO

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

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

70       This  page  is  part of release 5.07 of the Linux man-pages project.  A
71       description of the project, information about reporting bugs,  and  the
72       latest     version     of     this    page,    can    be    found    at
73       https://www.kernel.org/doc/man-pages/.
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77                                  2017-09-15                   BINDRESVPORT(3)