server: Reuse the raw socket #129
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## master #129 +/- ##
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- Coverage 35.06% 34.58% -0.48%
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Files 32 32
Lines 2045 2073 +28
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Hits 717 717
- Misses 1237 1265 +28
Partials 91 91
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Creating, then destroying a raw socket for every packet is very heavy. We can open the socket and keep it when first opening the listening socket, so that we are able to reuse it This however requires knowing and binding to an interface at socket creation time (which is fairly standard for dhcpv4) due to a limitation of the library we use Signed-off-by: Anatole Denis <anatole@unverle.fr>
When deferring to the system routing, the ip address is automatically selected by the kernel. We were previously using the message's ServerIPAddr, but that is incorrect as a source address since that is the address of the next server, and not necessarily the address of the current server or an address that is routable by the client Signed-off-by: Anatole Denis <anatole@unverle.fr>
Signed-off-by: Anatole Denis <anatole@unverle.fr>
With the deprecation of mdhlayer/raw and its replacement with mdhlayer/packet, we lost BSD support for AF_PACKET sockets Since the server code degrades gracefully if tryOpenRawSock fails, compile a stub to let the server compile and start outside linux Signed-off-by: Anatole Denis <anatole@unverle.fr>
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Creating, then destroying a raw socket for every packet is very heavy. We can open the socket and keep it when first opening the (udp) listening socket, so that we are able to reuse the raw socket for further packets
Instead of managing the packet socket with manual syscalls, we can use the https://github.com/mdlayher/raw library (which we already imported before anyway) which will give us portability for free.
This does however mean that we cannot support dynamically setting the interface differently for each packet (at the moment) as the library requires an interface when binding to the socket; so this requires binding to a specific interface at startup (rather than relying on out-of-band data when receiving packets to choose the outgoing interface).
For DHCP servers this is a very common behavior (and we even required it until not that long ago) so I'm happy to take that tradeoff until we can update the upstream library to support the other usecase if needed.
Finally, if we can't setup the raw socket, we can then fallback to sending over broadcast (which is allowed by the RFC), ensuring that the server can keep working without for example CAP_NET_RAW