bindresvport(3) Linux Man Page

Name

bindresvport - bind a socket to a privileged IP port

Library

Standard C library ( libc ", " -lc )

Synopsis

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

Description

bindresvport() is used to bind the socket referred to by the file descriptor sockfd to a privileged anonymous IP port, that is, a port number arbitrarily selected from the range 512 to 1023.

If the bind(2) performed by bindresvport() is successful, and sin is not NULL, then sin->sin_port returns the port number actually allocated.

sin can be NULL, in which case sin->sin_family is implicitly taken to be AF_INET .However, in this case, bindresvport() has no way to return the port number actually allocated. (This information can later be obtained using getsockname(2).)

Return Value

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

Errors

bindresvport() can fail for any of the same reasons as bind(2). In addition, the following errors may occur:

EACCES The calling process was not privileged (on Linux: the calling process did not have the CAP_NET_BIND_SERVICE capability in the user namespace governing its network namespace).

EADDRINUSE All privileged ports are in use.

EAFNOSUPPORT ( EPFNOSUPPORT in glibc 2.7 and earlier)
sin is not NULL and sin->sin_family is not AF_INET .

Attributes

For an explanation of the terms used in this section, see attributes(7). allbox; lb lb lbx T{ bindresvport()

Interface	Attribute	Value
T}	Thread safety	glibc\ >=\ 2.17: MT-Safe; glibc\ <\ 2.17: MT-Unsafe

The bindresvport() function uses a static variable that was not protected by a lock before glibc 2.17, rendering the function MT-Unsafe.

Versions

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

Notes

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

Standards

BSD.

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