bindresvport - bind a socket to a privileged IP port
#include <sys/types.h> #include <netinet/in.h> int bindresvport(int sockfd, struct sockaddr_in *sin);
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
If the bind(2) performed by
bindresvport() is successful, and
sin is not
sin->sin_port returns the port number actually
sin can be NULL, in which case
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
bindresvport() returns 0 on success; otherwise -1 is
errno set to indicate the cause of the error.
bindresvport() can fail for any of the same reasons as bind(2). In addition, the following errors may occur:
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).
All privileged ports are in use.
sin is not NULL and
sin->sin_family is not
For an explanation of the terms used in this section, see attributes(7).
|bindresvport()||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.
Not in POSIX.1. Present on the BSDs, Solaris, and many other systems.
Unlike some bindresvport() implementations, the
glibc implementation ignores any value that the caller supplies in
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