IPV6_PKTINFO socket option

The IPV6_PKTINFO socket option allows an application to enable or disable the return of packet information by the LPFN_WSARECVMSG (WSARecvMsg) function on an IPv6 socket..

To query the status of this socket option, call the getsockopt function. To set this option, call the setsockopt function with the following parameters.

Socket option value

The constant that represents this socket option is 19.

Syntax

int getsockopt(
  (SOCKET) s,      // descriptor identifying a socket 
  (int) IPPROTO_IPV6,   // level
  (int) IPV6_PKTINFO, // optname
  (char *) optval, // output buffer,
  (int) optlen,  // size of output buffer
);

int setsockopt(
  (SOCKET) s,      // descriptor identifying a socket 
  (int) IPPROTO_IPV6,   // level
  (int) IPV6_PKTINFO, // optname
  (char *) optval, // input buffer,
  (int) optlen,  // size of input buffer
);

Parameters

s [in]

A descriptor identifying the socket.

level [in]

The level at which the option is defined. Use IPPROTO_IPV6 for this operation.

optname [in]

The socket option for which to get or set the value. Use IPV6_PKTINFO for this operation.

optval [out]

A pointer to the buffer containing the value for the option to set. This parameter should point to buffer equal to or larger than the size of a DWORD value.

This value is treated as a boolean value with 0 used to indicate FALSE (disabled) and a nonzero value to indicate TRUE (enabled).

optlen [in, out]

A pointer to the size, in bytes, of the optval buffer. This size must be equal to or larger than the size of a DWORD value.

Return value

If the operation completes successfully, the getsockopt or setsockopt function returns zero.

If the operation fails, a value of SOCKET_ERROR is returned and a specific error code can be retrieved by calling WSAGetLastError.

Remarks

The getsockopt function called with the IPV6_PKTINFO socket option allows an application to determine if packet information is to be returned by the LPFN_WSARECVMSG (WSARecvMsg)function for an IPv6 socket.

The setsockopt function called with the IPV6_PKTINFO socket option allows an application to enable or disable the return of packet information by the LPFN_WSARECVMSG (WSARecvMsg) function. The IPV6_PKTINFO option for a socket is disabled (set to FALSE) by default.

When this socket option is enabled on an IPv6 socket of type SOCK_DGRAM or SOCK_RAW, the LPFN_WSARECVMSG (WSARecvMsg) function returns packet information in the WSAMSG structure pointed to by the lpMsg parameter. One of the control data objects in the returned WSAMSG structure will contain an in6_pktinfo structure used to store received packet address information.

For datagrams received by the LPFN_WSARECVMSG (WSARecvMsg) function over IPv6, the Control member of the WSAMSG structure received will contain a WSABUF structure that contains a WSACMSGHDR structure. The cmsg_level member of this WSACMSGHDR structure would contain IPPROTO_IPV6, the cmsg_type member of this structure would contain IPV6_PKTINFO, and the cmsg_data member would contain an in6_pktinfo structure used to store received IPv6 packet address information. The IPv6 address in the in6_pktinfo structure is the IPv6 address from which the packet was received.

For a dual-stack datagram socket, if an application requires the LPFN_WSARECVMSG (WSARecvMsg) function to return packet information in a WSAMSG structure for datagrams received over IPv4, then IP_PKTINFO socket option must be set to true on the socket. If only the IPV6_PKTINFO option is set to true on the socket, packet information will be provided for datagrams received over IPv6 but may not be provided for datagrams received over IPv4.

Note that the Ws2ipdef.h header file is automatically included in Ws2tcpip.h, and should never be used directly.

Requirements

See also

Dual-Stack Sockets

getsockopt

in6_pktinfo

IP_PKTINFO

IPPROTO_IPV6 Socket Options

setsockopt

socket

WSAMSG

LPFN_WSARECVMSG (WSARecvMsg)