RecvMsg.cmsg() should check MSG_CTRUNC

[Andy Grover]

If the cmsg buffer is too small, MSG_CTRUNC will be set in the header flags. This should be checked before returning CmsgIterator, or else the iterator might return invalid data.

[SteveLauC]

Hi, that indeed should be checked, do you have a good interface for this change in mind?

[Andy Grover]

Hi, that indeed should be checked, do you have a good interface for this change in mind?

I think the simplest thing, although an API change, would be to change RecvMsg::cmsgs() to return a Result<CmsgIterator> instead of a CmsgIterator, and return an error if MSG_CTRUNC was set.