BINDRESVPORT(3) - Linux man page online | Library functions

Bind a socket to a privileged IP port.

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


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 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. How‐ ever, in this case, bindresvport() has no way to return the port number actually allo‐ cated. (This information can later be obtained using getsockname(2).)


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


bindresvport() can fail for any of the same reasons as bind(2). In addition, the follow‐ ing 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.


For an explanation of the terms used in this section, see attributes(7). ┌───────────────┬───────────────┬─────────────────────────┐ │Interface │ Attribute │ Value │ ├───────────────┼───────────────┼─────────────────────────┤ │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 sin->sin_port.


bind(2), getsockname(2)


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2017-09-15 BINDRESVPORT(3)
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bindresvport(3) referred by bindresvport(3t)
refer to attributes(7) | bind(2) | getsockname(2)
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