VersionInfo: allow non-linkstamp rules to link in definitions

bazel/BUILD

@@ -227,6 +227,11 @@ config_setting(
     values = {"cpu": "ios_arm64e"},
 )
 
+config_setting(
+    name = "manual_stamp",
+    values = {"define": "manual_stamp=manual_stamp"},
+)
+
 alias(
     name = "apple",
     actual = select(

bazel/README.md

@@ -363,6 +363,10 @@ The following optional features can be enabled on the Bazel build command-line:
   `--define tcmalloc=debug`. Note this option cannot be used with FIPS-compliant mode BoringSSL.
 * Default [path normalization](https://github.com/envoyproxy/envoy/issues/6435) with
   `--define path_normalization_by_default=true`. Note this still could be disable by explicit xDS config.
+* Manual stamping via VersionInfo with `--define manual_stamp=manual_stamp`.
+  This is needed if the `version_info_lib` is compiled via a non-binary bazel rules, e.g `envoy_cc_library`.
+  Otherwise, the linker will fail to resolve symbols that are included via the `linktamp` rule, which is only available to binary targets.
+  This is being tracked as a feature in: https://github.com/envoyproxy/envoy/issues/6859.
 
 ## Disabling extensions
 

docs/root/intro/version_history.rst

@@ -18,7 +18,7 @@ Version history
 * redis: add support for Redis cluster custom cluster type.
 * redis: added :ref:`prefix routing <envoy_api_field_config.filter.network.redis_proxy.v2.RedisProxy.prefix_routes>` to enable routing commands based on their key's prefix to different upstream.
 * redis: add support for zpopmax and zpopmin commands.
-* redis: added 
+* redis: added
   :ref:`max_buffer_size_before_flush <envoy_api_field_config.filter.network.redis_proxy.v2.RedisProxy.ConnPoolSettings.max_buffer_size_before_flush>` to batch commands together until the encoder buffer hits a certain size, and
   :ref:`buffer_flush_timeout <envoy_api_field_config.filter.network.redis_proxy.v2.RedisProxy.ConnPoolSettings.buffer_flush_timeout>` to control how quickly the buffer is flushed if it is not full.
 * router: add support for configuring a :ref:`grpc timeout offset <envoy_api_field_route.RouteAction.grpc_timeout_offset>` on incoming requests.
@@ -28,6 +28,8 @@ Version history
   downstreams and that will not start before the global timeout.
 * runtime: added support for statically :ref:`specifying the runtime in the bootstrap configuration
   <envoy_api_field_config.bootstrap.v2.Runtime.base>`.
+* server: ``--define manual_stamp=manual_stamp`` was added to allow server stamping outside of binary rules.
+  more info in the `bazel docs <https://github.com/envoyproxy/envoy/blob/master/bazel/README.md#enabling-optional-features>`_.
 * upstream: added :ref:`upstream_cx_pool_overflow <config_cluster_manager_cluster_stats>` for the connection pool circuit breaker.
 * upstream: an EDS management server can now force removal of a host that is still passing active
   health checking by first marking the host as failed via EDS health check and subsequently removing

source/common/common/BUILD

@@ -251,6 +251,23 @@ genrule(
     cmd = """echo "#define BUILD_VERSION_NUMBER \\"$$(cat $<)\\"" >$@""",
 )
 
+genrule(
+    name = "generate_version_linkstamp",
+    outs = ["lib/version_linkstamp.h"],
+    cmd = "$(location //source/common/common:generate_version_linkstamp.sh) >> $@",
+    # Undocumented attr to depend on workspace status files.
+    # https://github.com/bazelbuild/bazel/issues/4942
+    # Used here because generate_version_linkstamp.sh depends on the workspace status files.
+    stamp = 1,
+    tools = ["//source/common/common:generate_version_linkstamp.sh"],
+)
+
+genrule(
+    name = "generate_version_linkstamp_empty",
+    outs = ["empty/version_linkstamp.h"],
+    cmd = """>$@""",
+)
+
 envoy_cc_library(
     name = "version_includes",
     hdrs = [
@@ -262,11 +279,21 @@ envoy_cc_library(
 envoy_cc_library(
     name = "version_lib",
     srcs = ["version.cc"],
+    hdrs = select({
+        "//bazel:manual_stamp": [":generate_version_linkstamp"],
+        # By default the header file is empty.
+        # This is done so that the definitions linked via the linkstamp rule don't cause collisions.
+        "//conditions:default": [":generate_version_linkstamp_empty"],
+    }),
     copts = envoy_select_boringssl(
         ["-DENVOY_SSL_VERSION=\\\"BoringSSL-FIPS\\\""],
         ["-DENVOY_SSL_VERSION=\\\"BoringSSL\\\""],
     ),
     linkstamp = "version_linkstamp.cc",
+    strip_include_prefix = select({
+        "//bazel:manual_stamp": "lib",
+        "//conditions:default": "empty",
+    }),
     deps = [
         ":version_includes",
         "//source/common/common:macros",

source/common/common/generate_version_linkstamp.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+# This script generates a header file that is used by version_lib whenever linkstamp is not allowed.
+# linkstamp is used to link in version_linkstamp.cc into the version_lib.
+# However, linkstamp is not available to non-binary bazel targets.
+# This means that if the topmost target being used to compile version_lib is a envoy_cc_library or related, linkstamp will not be in effect.
+# In turn this means that version_linkstamp.cc is not linked, and the build_scm_revision and build_scm_status are unknown symbols to the linker.
+
+# Unfortunately linkstamp is not well documented (https://github.com/bazelbuild/bazel/issues/2893).
+# But following the implicit trail one can deduce that linkstamp is in effect when "stamping" (https://github.com/bazelbuild/bazel/issues/2893) is on.
+# envoy_cc_library -- and the underlying cc_library rule -- does not support "stamping".
+# This makes sense as stamping mainly makes sense in the context of binaries for production releases, not static libraries.
+build_scm_revision=$(grep BUILD_SCM_REVISION bazel-out/volatile-status.txt | sed 's/^BUILD_SCM_REVISION //' | tr -d '\\n')
+
+echo "extern const char build_scm_revision[];"
+echo "extern const char build_scm_status[];"
+echo "const char build_scm_revision[] = \"$build_scm_revision\";"
+echo "const char build_scm_status[] = \"Library\";"

source/common/common/version.cc

@@ -4,6 +4,7 @@
 
 #include "common/common/fmt.h"
 #include "common/common/macros.h"
+#include "common/common/version_linkstamp.h"
 
 extern const char build_scm_revision[];
 extern const char build_scm_status[];