gnoi/os: add functionality to download from remote

os/BUILD.bazel

@@ -29,6 +29,7 @@ proto_library(
     import_prefix = "github.com/openconfig/gnoi",
     deps = [
         "//bootconfig:bootconfig_proto",
+        "//common:common_proto",
         "//types:types_proto",
     ],
 )
@@ -55,6 +56,7 @@ go_proto_library(
     proto = ":os_proto",
     deps = [
         "//bootconfig",
+        "//common",
         "//types",
     ],
 )

os/os.proto

@@ -18,9 +18,9 @@ syntax = "proto3";
 package gnoi.os;
 
 import "github.com/openconfig/gnoi/bootconfig/bootconfig.proto";
+import "github.com/openconfig/gnoi/common/common.proto";
 import "github.com/openconfig/gnoi/types/types.proto";
 
-
 option go_package = "github.com/openconfig/gnoi/os";
 
 option (types.gnoi_version) = "0.1.4";
@@ -136,6 +136,20 @@ service OS {
   //                  TransferEnd -->
   //                              <-- [Validated|InstallError]
   //
+  // Rather than transferring a file, clients may initiate a remote download
+  // of the OS package if the requested OS package is not present (on either
+  // supervisor).
+  // After the package is downloaded, the target will respond with Validated
+  // (or InstallError if the download failed).
+  // This scenario applies to both single and dual supervisor targets.
+  //
+  //         Client :--------------|--------------> Target
+  //              TransferRequest -->
+  //                              <-- [TransferReady|InstallError]
+  //            remote_download  -->
+  //                               ...
+  //                              <-- [Validated|InstallError]
+  //
   rpc Install(stream InstallRequest) returns (stream InstallResponse);
 
   // Activate sets the requested OS version as the version which is used at the
@@ -161,6 +175,9 @@ message InstallRequest {
     TransferRequest transfer_request = 1;
     bytes transfer_content = 2;
     TransferEnd transfer_end = 3;
+
+    // Details for the device to download the image from a remote location
+    common.RemoteDownload remote_download = 4;
   }
 }