>A TCP/IP stack is used by a network card driver. All incoming packets are
>stuffed into a Packet object and passed to the TCP/IP stack.
How would you evision multithreading in such an environment?
I'm currently toying with the idea of giving every interface it's own
thread and it's own objects (that would give me a neat Multiple
Cache/Local Replacement ARP cache and some other link level enhancements
when we'll support other hardware then ethernet.).
The problem is that this model grinds to a halt when it comes to the IP layer.
IP is responsible for distributing packets among interfaces, and can
therefore not be bound to any of them.
The only thing that comes to mind is to have a single IP object that queues
incoming packets for all interfaces. This requires strict serialisation on
the incoming_packet() functions. A thread that lives in IP could then
handle the packets (route them through, drop them or reassemble them and
queue them to TCP/UDP objects that eventually put them into user space
buffers).
Does anyone see a problem with this strategy? Speak up now if you do!
>From the other perspective of a sparsely populated array of PacketQueues, a
>PacketQueue is also a PacketListener. A packet queue is available
>(virtually) at every IP port (from 0 to 65,565).
Hmm, IP does not have ports. UDP and TCP do. This structure belongs over
there when i get there :)
Btw, quick update.
I finally got the linux kernel to let me bind a PF_PACKET socket to a
specific interface, so multiple interfaces support is coming up, probably
with the scheme outlined above.
I implemented a quick ARP cache that violates every RFC in the book, but
sort of does something. I would like to let it respond to ARP queries to
try and get it to bind an IP adress other than the linux card one. I hope
linux does not go bananas with this, but since i get the packets before
they go through the linux stack i give myself decent odds of doing this :)
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