nixos/testing: improve wording of `vsockOffset` description

Co-authored-by: Jacek Galowicz <jacek@galowicz.de>

Changed files
+8 -6
nixos
lib
testing
modules
+4 -3
nixos/lib/testing/nodes.nix
···
default = 2;
type = types.ints.between 2 4294967296;
description = ''
-
By default this assigns vsock numbers starting at 3 to the nodes.
-
On e.g. large builders used by multiple people, this would cause conflicts
-
between multiple users doing interactive debugging.
+
This field is only relevant when multiple users run the (interactive)
+
driver outside the sandbox and with the SSH backdoor activated.
+
The typical symptom for this being a problem are error messages like this:
+
`vhost-vsock: unable to set guest cid: Address already in use`
This option allows to assign an offset to each vsock number to
resolve this.
+4 -3
nixos/modules/testing/test-instrumentation.nix
···
default = 2;
type = types.ints.between 2 4294967296;
description = ''
-
By default this assigns vsock numbers starting at 3 to the nodes.
-
On e.g. large builders used by multiple people, this would cause conflicts
-
between multiple users doing interactive debugging.
+
This field is only relevant when multiple users run the (interactive)
+
driver outside the sandbox and with the SSH backdoor activated.
+
The typical symptom for this being a problem are error messages like this:
+
`vhost-vsock: unable to set guest cid: Address already in use`
This option allows to assign an offset to each vsock number to
resolve this.