Increase the MTU on the virtual ethernet link #176
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There are currently 2 important uses of `mtu` in the current code: 1. the maximum UDP datagram size we promise to send without fragmentation. <-- this has been renamed `safe_outgoing_mtu` 2. the MTU on the virtual ethernet link to the VM. This is a link-local concern since we proxy the TCP streams. Signed-off-by: David Scott <dave.scott@docker.com>
This adds support for the database key com.docker.driver.amd64-linux/slirp/mtu The default value is unchanged (1500). Signed-off-by: David Scott <dave.scott@docker.com>
This is from mirage/mirage-tcpip#288 mirage/mirage-protocols#4 Signed-off-by: David Scott <dave.scott@docker.com>
The `connect` parameter is optional so we must supply it. Signed-off-by: David Scott <dave.scott@docker.com>
This is the MTU on the local virtual ethernet link, not the "safe outgoing MTU" which is used for datagram forwarding. We would like the MTU on this link to be large to reduce the processing overhead per byte of payload, however the maximum safe read and write size on Hyper-V sockets seems to be 8192; therefore pick a round number < 8192. Signed-off-by: David Scott <dave.scott@docker.com>
Signed-off-by: David Scott <dave@recoil.org>
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This PR separates the MTU used for outgoing datagram traffic (for which we need to respect the Do Not Fragment bit) from the MTU used on the internal virtual ethernet link and bumps the latter to 8000. This should allow the TCP stack to use a larger segment size and to reduce the overhead per byte of payload.
This PR also allows the virtual ethernet MTU to be set via the database key
com.docker.driver.amd64-linux/slirp/mtuNote this PR references a port of mirage/mirage-protocols#4 and mirage/mirage-tcpip#288 but we need to do some rebasing work for the v3 release anyway.