[ECOS] RE: TCP/IP Stack packet regrouping

[ECOS] RE: TCP/IP Stack packet regrouping

[Anthony Massa]

These are fields in the IP header for handling fragmentation.  I believe the
IP_DF field is the Don't Fragment flag.  In that case, if the MTU below the
IP layer is not big enough to hold all of the data, it will not be sent on
the link.

>I just looked, and it bases it on if_mtu if it's a broadcast packet.  I
>don't understand the code below though because I don't know what ip_off
>or IP_DF are.  I might look them up at a later time though.  I'm
>primarily doing documentation/design for networking right now so I don't
>have time for this at the moment.

	if (ip->ip_off & IP_DF) {	// Line 847 of ip_output.c
		error = EMSGSIZE;
		ipstat.ips_cantfrag++;
		goto bad;
	}
	len = (ifp->if_mtu - hlen) &~ 7;
	if (len < 8) {
		error = EMSGSIZE;
		goto bad;
	}