Need a way to set socket options for replies to individual down-streams of listeners #38208
Description
Need a way to set socket options for replies to individual down-streams of listeners
Description:
We have a requirement to set dscp socket option for traffic outbound from istio gateway, we are able to set for outbound traffic using cluster names, as follows ->
apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
spec:
configPatches:
- applyTo: CLUSTER
match:
cluster:
name: outbound|80||testcluster
patch:
operation: MERGE
value:
upstream_bind_config:
socket_options:
- int_value: 64
level: 0
name: 1
state: STATE_PREBIND
source_address:
address: 0.0.0.0
port_value: 0
However, how to do this for replies to downstream? (HTTP replies in our case) There's no cluster names for that, it's only possible to set one socket_options once for listener.
We've been working around that by patching envoy to read dscp value from http header for replies,
diff -urNp envoy/source/common/router/router.cc envoy-patched/source/common/router/router.cc
--- envoy/source/common/router/router.cc 2024-11-26 13:27:07.779636678 +0000
+++ envoy-patched/source/common/router/router.cc 2025-01-10 09:19:59.583055171 +0000
@@ -1685,6 +1687,41 @@ void Filter::onUpstreamHeaders(uint64_t
// provide finalizeResponseHeaders functions on the Router::Config and VirtualHost interfaces.
route_entry_->finalizeResponseHeaders(*headers, callbacks_->streamInfo());
+ static constexpr const char* dscpHeaderStr = "x-differentiated-services-code-point";
+ static const Http::LowerCaseString s_dscpHdrStr(dscpHeaderStr);
+ auto getResult = headers->get(s_dscpHdrStr);
+ if (!getResult.empty())
+ {
+ uint64_t dscp = 0;
+ if (absl::SimpleAtoi(getResult[0]->value().getStringView(), &dscp)) {
+ auto connection = const_cast<Network::Connection*>(callbacks_->connection().ptr());
+
+ dscp = (dscp << 2);
+ std::unique_ptr<Network::Socket::Options> options = std::make_unique<Network::Socket::Options>();
+ options->push_back(std::make_shared<Network::AddrFamilyAwareSocketOptionImpl>(
+ envoy::config::core::v3::SocketOption::STATE_PREBIND,
+ ENVOY_SOCKET_IP_TOS,
+ ENVOY_SOCKET_IPV6_TCLASS,
+ dscp));
+
+ dynamic_cast<Network::ConnectionImpl*>(connection)->setSocketOptions(std::move(options),
+ envoy::config::core::v3::SocketOption::STATE_PREBIND);
+ }
+ headers->remove(s_dscpHdrStr);
+ }
We wanted to know ->
- Is there any way to configure socket_options for connections made by listener to different downstreams?
- If not, would it okay to implement this in a filter? Perhaps a http filter that does something like the above code snippet?