* [PATCH nixpkgs] spectrumPackages: use link-local router addresses
@ 2021-05-13 20:13 Alyssa Ross
2021-05-14 16:52 ` Cole Helbling
0 siblings, 1 reply; 2+ messages in thread
From: Alyssa Ross @ 2021-05-13 20:13 UTC (permalink / raw)
To: devel
There's no need for every interface on a router to have it's own
unique IP. Using link-local addresses, we can assign every interface
on a single router the same IP, and save the effort of
adding/subtracting one all the time to infer the address of one side
of a link from the other.
This means that routers and clients are both only interested in what
the IP of the client should be, since that's the only thing that is
different between different links. So we change our MAC format to
communicate the client IP to both sides. If we just made the whole
NIC portion of the MAC the last three octets of an IP address like we
did before, then both ends of the link would have the same MAC, so we
still need to set a bit to encode whether a MAC is at the router side
of the link or the client side. I've decided to simplify the
implementation by using the most significant bit of the NIC part for
that, and just declaring the rest of that octet to be reserved. This
way, no calculation is required in the guests -- they just need to
look at the last two octets. And we can still identify 65536 links in
this scheme, which should be enough for anybody, right?
---
I'd like to move the networking to be IPv6. That's a bit more
complicated, but shouldn't get in the way of smaller improvements like
this.
.../linux/spectrum/testhost/default.nix | 25 ++++++++-----------
.../linux/spectrum/vm/app/default.nix | 15 ++++-------
.../linux/spectrum/vm/net/default.nix | 13 +++++-----
3 files changed, 23 insertions(+), 30 deletions(-)
diff --git a/pkgs/os-specific/linux/spectrum/testhost/default.nix b/pkgs/os-specific/linux/spectrum/testhost/default.nix
index 21c585f1490..de62f0add67 100644
--- a/pkgs/os-specific/linux/spectrum/testhost/default.nix
+++ b/pkgs/os-specific/linux/spectrum/testhost/default.nix
@@ -45,23 +45,20 @@ let
if { ip link set br0 up }
# Calculate the MACs for our TAP and the router's TAP.
- backtick -in router_nic_dec {
- expr ${toString sys-vms.app.vmID} * 2 + 64 * 256 * 256
- }
- backtick -in client_nic_dec {
- expr ${toString sys-vms.app.vmID} * 2 + 64 * 256 * 256 + 1
- }
- multisubstitute {
- importas -iu router_nic_dec router_nic_dec
- importas -iu client_nic_dec client_nic_dec
- }
+ # MAC address format, by octet:
+ #
+ # 0-3 Static OUI for Spectrum
+ # 4 Most significant bit is used to differentiate
+ # routers from clients. Other bits are reserved.
+ # 5-6 Last two octets of client's IP (in 100.64.0.0/16).
+ #
backtick -i router_mac {
- pipeline { printf %x $router_nic_dec }
- sed s/^\\(..\\)\\(..\\)\\(..\\)$/0A:B3:EC:\\1:\\2:\\3/
+ pipeline { printf %.4x ${toString sys-vms.app.vmID} }
+ sed s/^\\(..\\)\\(..\\)$/0A:B3:EC:80:\\1:\\2/
}
backtick -i client_mac {
- pipeline { printf %x $client_nic_dec }
- sed s/^\\(..\\)\\(..\\)\\(..\\)$/0A:B3:EC:\\1:\\2:\\3/
+ pipeline { printf %.4x ${toString sys-vms.app.vmID} }
+ sed s/^\\(..\\)\\(..\\)$/0A:B3:EC:00:\\1:\\2/
}
multisubstitute {
importas -iu router_mac router_mac
diff --git a/pkgs/os-specific/linux/spectrum/vm/app/default.nix b/pkgs/os-specific/linux/spectrum/vm/app/default.nix
index 65dbb51f5e1..f8ff480932c 100644
--- a/pkgs/os-specific/linux/spectrum/vm/app/default.nix
+++ b/pkgs/os-specific/linux/spectrum/vm/app/default.nix
@@ -28,20 +28,15 @@ runCommand "vm-app" rec {
up = writeText "net-up" ''
backtick -i LOCAL_IP {
pipeline { ip -j link show eth0 }
- pipeline { jq -r ".[0].address | split(\":\") | .[3:6] | \"0x\" + .[]" }
- xargs printf "100.%d.%d.%d"
+ pipeline { jq -r ".[0].address | split(\":\") | .[4:6] | \"0x\" + .[]" }
+ xargs printf "100.64.%d.%d"
}
importas -iu LOCAL_IP LOCAL_IP
- backtick -i REMOTE_IP {
- jq -jn --arg localip $LOCAL_IP
- "$localip | split(\".\") | .[3] |= tonumber - 1 | join(\".\")"
- }
- importas -iu REMOTE_IP REMOTE_IP
-
- if { ip address add ''${LOCAL_IP}/31 dev eth0 }
+ if { ip address add ''${LOCAL_IP}/32 dev eth0 }
if { ip link set eth0 up }
- ip route add default via $REMOTE_IP
+ if { ip route add 169.254.0.1 dev eth0 }
+ ip route add default via 169.254.0.1 dev eth0
'';
};
diff --git a/pkgs/os-specific/linux/spectrum/vm/net/default.nix b/pkgs/os-specific/linux/spectrum/vm/net/default.nix
index 1deb7031caf..5921b62fcf7 100644
--- a/pkgs/os-specific/linux/spectrum/vm/net/default.nix
+++ b/pkgs/os-specific/linux/spectrum/vm/net/default.nix
@@ -54,15 +54,16 @@ runCommand "vm-net" rec {
# Our IP is encoded in the NIC-specific portion of the
# interface's MAC address.
- backtick -i LOCAL_IP {
+ backtick -i CLIENT_IP {
pipeline { ip -j link show $INTERFACE }
- pipeline { jq -r ".[0].address | split(\":\") | .[3:6] | \"0x\" + .[]" }
- xargs printf "100.%d.%d.%d"
+ pipeline { jq -r ".[0].address | split(\":\") | .[4:6] | \"0x\" + .[]" }
+ xargs printf "100.64.%d.%d"
}
- importas -iu LOCAL_IP LOCAL_IP
+ importas -iu CLIENT_IP CLIENT_IP
- if { ip address add ''${LOCAL_IP}/31 dev $INTERFACE }
- ip link set $INTERFACE up
+ if { ip address add 169.254.0.1/32 dev $INTERFACE }
+ if { ip link set $INTERFACE up }
+ ip route add $CLIENT_IP dev $INTERFACE
}
{
--
2.31.1
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH nixpkgs] spectrumPackages: use link-local router addresses
2021-05-13 20:13 [PATCH nixpkgs] spectrumPackages: use link-local router addresses Alyssa Ross
@ 2021-05-14 16:52 ` Cole Helbling
0 siblings, 0 replies; 2+ messages in thread
From: Cole Helbling @ 2021-05-14 16:52 UTC (permalink / raw)
To: Alyssa Ross, devel
On Thu May 13, 2021 at 1:13 PM PDT, Alyssa Ross wrote:
> There's no need for every interface on a router to have it's own
> unique IP. Using link-local addresses, we can assign every interface
> on a single router the same IP, and save the effort of
> adding/subtracting one all the time to infer the address of one side
> of a link from the other.
>
> This means that routers and clients are both only interested in what
> the IP of the client should be, since that's the only thing that is
> different between different links. So we change our MAC format to
> communicate the client IP to both sides. If we just made the whole
> NIC portion of the MAC the last three octets of an IP address like we
> did before, then both ends of the link would have the same MAC, so we
> still need to set a bit to encode whether a MAC is at the router side
> of the link or the client side. I've decided to simplify the
> implementation by using the most significant bit of the NIC part for
> that, and just declaring the rest of that octet to be reserved. This
> way, no calculation is required in the guests -- they just need to
> look at the last two octets. And we can still identify 65536 links in
> this scheme, which should be enough for anybody, right?
> ---
> I'd like to move the networking to be IPv6. That's a bit more
> complicated, but shouldn't get in the way of smaller improvements like
> this.
>
> .../linux/spectrum/testhost/default.nix | 25 ++++++++-----------
> .../linux/spectrum/vm/app/default.nix | 15 ++++-------
> .../linux/spectrum/vm/net/default.nix | 13 +++++-----
> 3 files changed, 23 insertions(+), 30 deletions(-)
Reviewed-by: Cole Helbling <cole.e.helbling@outlook.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-05-13 20:13 [PATCH nixpkgs] spectrumPackages: use link-local router addresses Alyssa Ross
2021-05-14 16:52 ` Cole Helbling
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