BUG: Setsockopt with IP_MULTICAST_IF Works for Invalid Address (196351)
The information in this article applies to:
- Microsoft Platform Software Development Kit (SDK) 1.0, when used with:
- the operating system: Microsoft Windows NT 4.0
- the operating system: Microsoft Windows 2000
This article was previously published under Q196351 SYMPTOMS
The IP_MULTICAST_IF option and an IP address are passed to the setsockopt()
API to specify which interface should be used for outgoing multicast
packets. If you attempt to set this option to an invalid IP address, the
function does not return an error.
This occurs only if setsockopt is called before bind. Once the socket is
bound to a local interface, if you attempt to set the multicast interface
to an invalid address, it fails.
CAUSE
Winsock itself does not recognize addresses. The TCP/IP stack does not
validate the address supplied until a call to bind is made. Although
setsockopt with invalid IP address succeeds, the subsequent bind fails.
RESOLUTION
Ensure that the interface supplied to setsockopt is valid. Use the Winsock
ioctl command SIO_GET_INTERFACE_LIST to obtain a list of valid interface
addresses.
NOTE: This ioctl is only available in Winsock 2.
STATUS
Microsoft has confirmed this to be a problem in the Microsoft products
listed at the beginning of this article.
| Modification Type: | Minor | Last Reviewed: | 7/11/2005 |
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| Keywords: | kbAPI kbBug kbnetwork kbWinsock KB196351 |
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