bindresvport(3)

1bindresvport(3)            Library Functions Manual            bindresvport(3)
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NAME

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

9       Standard C library (libc, -lc)
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SYNOPSIS

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

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

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

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

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

64       Present on the BSDs, Solaris, and many other systems.
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NOTES

67       Unlike  some  bindresvport()  implementations, the glibc implementation
68       ignores any value that the caller supplies in sin->sin_port.
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STANDARDS

71       BSD.
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