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From: "Mark Delany" <c2h@romeo.emu.st>
To: freebsd-net@freebsd.org
Subject: Re: Does FreeBSD have sendmmsg or recvmmsg system calls?
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> Why is a signal lost in the scenario you described ?

Because the return can only indicate a signal/error *or* a batch of
messages but not both and the semantics of recvmsg() means that both
could occur.

Don't just consider signals, consider any -1/errno return from
recvmsg() such as -1/EAGAIN or -1/ENOBUFS or -1/EFAULT.

If one emulates recvmmsg() via multiple calls to recvmsg() and the
emulation receives 'n' messages via recvmsg() then gets a -1/EFAULT
return on message 'n'+1 then what does it return to the caller?

If it returns 'n' messages then the EFAULT is lost.

If it returns -1/EFAULT then the 'n' messages are lost.


Mark.