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fix: UDPSClient uses two-arg Join so multicast receiver lands on the right interface

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UDPSClient::ConnectMulticast was calling the single-arg BasicUDPSocket::Join,
which forwards NULL as the local interface and lets the kernel bind to
INADDR_ANY.  On a multi-homed host (or when the server sends on loopback via
Interface = "127.0.0.1") the client joins the wrong interface and silently
receives nothing.

Fix: read the optional Interface key inside the useMulticast block in
UDPSClient::Initialise; in ConnectMulticast call the two-arg
Join(group, interface) when Interface is set, and fall back to the one-arg
call otherwise to preserve the existing INADDR_ANY behaviour for configs that
omit it.

Forward the new optional Interface key through UDPStreamerClient (read from
DataSource config, written into the UDPSClient ConfigurationDatabase only
when non-empty).  Extend the "Joined multicast group" log to report the
interface name or "default".

Regression test TestExecute_MulticastReceivesDataOnInterface: mock TCP
control listener + multicast UDP DATA socket with IP_MULTICAST_IF set to
127.0.0.1, verifying a uint32 value of 424242 reaches DataSource signal
memory.  Confirmed FAILED without the Join fix and PASSED with it.

Suite: 133/133 (was 132/132 before this commit).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Martino Ferrari
2026-08-17 08:23:41 +02:00
co-authored by Claude Sonnet 4.6
parent 61a2aa3988
commit 14d5351a81
8 changed files with 270 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Source/Components/Interfaces/UDPStream/UDPSClient.cpp
+12 -3
View File
@@ -85,6 +85,9 @@ bool UDPSClient::Initialise(StructuredDataI &data) {
uint32 dpU32 = static_cast<uint32>(serverPort) + 1u;
(void) data.Read("DataPort", dpU32);
dataPort = static_cast<uint16>(dpU32);
StreamString iface;
(void) data.Read("Interface", iface);
multicastInterface = iface;
}
float32 silenceS = UDPS_CLIENT_DEFAULT_SILENCE_TIMEOUT_S;
@@ -311,7 +314,12 @@ bool UDPSClient::ConnectMulticast() {
return false;
}
ok = mcastSocket.Join(multicastGroup.Buffer());
if (multicastInterface.Size() > 0u) {
ok = mcastSocket.Join(multicastGroup.Buffer(), multicastInterface.Buffer());
}
else {
ok = mcastSocket.Join(multicastGroup.Buffer());
}
if (!ok) {
REPORT_ERROR_STATIC(ErrorManagement::Warning,
"UDPSClient: Could not join multicast group %s.",
@@ -320,8 +328,9 @@ bool UDPSClient::ConnectMulticast() {
return false;
}
REPORT_ERROR_STATIC(ErrorManagement::Information,
"UDPSClient: Joined multicast group %s on port %u.",
multicastGroup.Buffer(), static_cast<uint32>(dataPort));
"UDPSClient: Joined multicast group %s on port %u via interface %s.",
multicastGroup.Buffer(), static_cast<uint32>(dataPort),
(multicastInterface.Size() > 0u) ? multicastInterface.Buffer() : "default");
// Now open the TCP control connection and announce ourselves
if (!tcpSocket.Open()) {