Setting DF bit in IP header.

Hello All,

Can any body tell me, How to set the DF bit for IP header over Linux
OS. As right now I am using setsockopt(), with option IP_MTU_DISCOVER
and optval as IP_PMTUDISC_DO. Like,

int optval = IP_PMTUDISC_DO;
err_code = setsockopt(socket,
SOL_IP,
IP_MTU_DISCOVER,
&optval,
sizeof(int));

But this option also forces the PMTUD for the given socket, that I
don't want. This PMTUD I am implementing by my own.

So can you tell me any other way to set it ON.

I am also not intrested in setting IP_HDRINCL option, to provide my
own IP header while sending, for just setting the DF bit value.

Thanks in advance.

Rajat.