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UDP session filters can't access the addresses on the first packet #41186

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#41245
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UDP session filters can't access the addresses on the first packet#41186
#41245
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area/udpbug
@lilmayofuksu

Description

@lilmayofuksu
lilmayofuksu
opened on Sep 23, 2025

Or "UdpRecvData::addresses_ becomes empty after createSession in StickySessionUdpProxyFilter::onDataInternal"

Description:

envoy/source/extensions/filters/udp/udp_proxy/udp_proxy_filter.cc

Lines 84 to 90 in 8b38e06

Network::FilterStatus StickySessionUdpProxyFilter::onDataInternal(Network::UdpRecvData& data) {
bool defer_socket = config_->hasSessionFilters() || config_->tunnelingConfig();
const auto active_session_it = sessions_.find(data.addresses_);
ActiveSession* active_session;
if (active_session_it == sessions_.end()) {
active_session = createSession(std::move(data.addresses_), nullptr, defer_socket);
if (active_session == nullptr) {

In this function, data.addresses_ is moved after a new session gets created. This causes data.addresses_ to be empty and because of it, UDP session filters won't be able to access them.

This only affects the first packet received from the peer.

Repro steps:

Create or re-use an existing UDP session filter that implements onData and log the pointers of data.addresses_.peer_ and data.addresses_.local_

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