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From: Sam <sah@softcardsystems.com>
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Subject: Re: mbuf w/o pkthdr?
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>> Are all packets supposed to have the M_PKTHDR flag?  Why?
>
> IIRC, M_PKTHDR indicates the first mbuf in a chain when a packet is
> split across multiple mbufs.  This usually only happens for outgoing
> packets, where protocol headers are constructed in separate mbufs
> which are prepended to the chain as the packet moves down the stack.

That's kind of my understanding (with some PACKET_TAG* stuff going on).

I don't have split headers, though.  Neither would an arp frame, but
he too gets a packet header and fills it out.

I don't mind following suit, I'm just wondering what the convention is
for.  Perhaps we use mbufs without packet headers for something special?

Sam