From d7635413410761a6866c6b39b5bbe8642a6f5643 Mon Sep 17 00:00:00 2001
From: bsbevins <145619550+bsbevins@users.noreply.github.com>
Date: Wed, 8 Oct 2025 09:57:30 -0500
Subject: [PATCH] Allow CA clients to determine the server protocol version
 (#711)

* Allow CA clients to determine the server protocol version

Adds a call to the CA client API that allows a client to determine the server's
protocol minor version number. This is needed to allow the ca-nameserver to
report a server's protocol version correctly to a client.

* ca_host_minor_protocol return for disconnected channels

ca_host_minor_protocol now explicitly returns CA_UKN_MINOR_VERSION for a disconnected channel.
---
 modules/ca/src/client/cac.h                |  7 +++++++
 modules/ca/src/client/cacChannel.cpp       |  7 +++++++
 modules/ca/src/client/cacIO.h              |  3 ++-
 modules/ca/src/client/cadef.h              | 11 +++++++++++
 modules/ca/src/client/nciu.cpp             |  7 +++++++
 modules/ca/src/client/nciu.h               |  2 ++
 modules/ca/src/client/netiiu.cpp           |  6 ++++++
 modules/ca/src/client/netiiu.h             |  2 ++
 modules/ca/src/client/oldAccess.h          |  2 ++
 modules/ca/src/client/oldChannelNotify.cpp | 10 ++++++++++
 modules/ca/src/client/tcpiiu.cpp           |  7 +++++++
 modules/ca/src/client/udpiiu.cpp           |  6 ++++++
 modules/ca/src/client/udpiiu.h             |  4 +++-
 modules/ca/src/client/virtualCircuit.h     |  2 ++
 14 files changed, 74 insertions(+), 2 deletions(-)

diff --git a/modules/ca/src/client/cac.h b/modules/ca/src/client/cac.h
index 79dcbaa9b..8fcb7c563 100644
--- a/modules/ca/src/client/cac.h
+++ b/modules/ca/src/client/cac.h
@@ -203,6 +203,7 @@ public:
     void destroyIIU ( tcpiiu & iiu );
 
     const char * pLocalHostName ();
+    const resTable < tcpiiu, caServerID > & getServerTable();
 
 private:
     epicsSingleton < localHostName > :: reference _refLocalHostName;
@@ -424,4 +425,10 @@ inline double cac ::
     return this->connTMO;
 }
 
+inline const resTable < tcpiiu, caServerID > & cac ::
+    getServerTable()
+{
+    return this->serverTable;
+}
+
 #endif // ifndef INC_cac_H
diff --git a/modules/ca/src/client/cacChannel.cpp b/modules/ca/src/client/cacChannel.cpp
index 33345967c..a76d6e957 100644
--- a/modules/ca/src/client/cacChannel.cpp
+++ b/modules/ca/src/client/cacChannel.cpp
@@ -129,6 +129,13 @@ unsigned cacChannel::getHostName (
     return 0u;
 }
 
+unsigned cacChannel::getHostMinorProtocol ( 
+    epicsGuard < epicsMutex > &) const throw ()
+{
+    epicsThreadOnce ( & cacChannelIdOnce, cacChannelSetup, 0);
+    return 0u;
+}
+
 // the default is to assume that it is a locally hosted channel
 const char * cacChannel::pHostName (
     epicsGuard < epicsMutex > & ) const throw ()
diff --git a/modules/ca/src/client/cacIO.h b/modules/ca/src/client/cacIO.h
index 760d8dd72..777155047 100644
--- a/modules/ca/src/client/cacIO.h
+++ b/modules/ca/src/client/cacIO.h
@@ -246,7 +246,8 @@ public:
     // !! deprecated, avoid use  !!
     virtual const char * pHostName (
         epicsGuard < epicsMutex > & guard ) const throw ();
-
+    virtual unsigned getHostMinorProtocol (
+        epicsGuard < epicsMutex > &) const throw () ;
     // exceptions
     class badString {};
     class badType {};
diff --git a/modules/ca/src/client/cadef.h b/modules/ca/src/client/cadef.h
index e7ab45cbe..5c60a06f7 100644
--- a/modules/ca/src/client/cadef.h
+++ b/modules/ca/src/client/cadef.h
@@ -1460,6 +1460,17 @@ LIBCA_API const char * epicsStdCall ca_host_name (chid channel);
 LIBCA_API unsigned epicsStdCall ca_get_host_name ( chid pChan, 
     char *pBuf, unsigned bufLength );
 
+/** \brief Return the minor protocol version number used by the host to
+ *  which a channel is cuurently connected.   
+ *
+ * \param[in] pChan channel identifier
+ * \returns The minor protocol version number.
+ * If the channel is disconnected CA_UKN_MINOR_VERSION is returned.
+ */
+LIBCA_API unsigned epicsStdCall ca_host_minor_protocol (chid pChan);
+
+#define HAS_CA_HOST_MINOR_PROTOCOL
+
 /** \brief Call their function with their argument whenever
  *  a new fd is added or removed.
  *
diff --git a/modules/ca/src/client/nciu.cpp b/modules/ca/src/client/nciu.cpp
index a862cb228..fc5d3cb4c 100644
--- a/modules/ca/src/client/nciu.cpp
+++ b/modules/ca/src/client/nciu.cpp
@@ -410,6 +410,13 @@ const char * nciu::pHostName (
     return this->piiu->pHostName ( guard );
 }
 
+unsigned nciu::getHostMinorProtocol (
+    epicsGuard < epicsMutex > & guard) const throw ()
+{
+    return this->piiu->getHostMinorProtocol (
+        guard );
+}
+
 bool nciu::ca_v42_ok (
     epicsGuard < epicsMutex > & guard ) const
 {
diff --git a/modules/ca/src/client/nciu.h b/modules/ca/src/client/nciu.h
index d909aa917..7e94fe1b8 100644
--- a/modules/ca/src/client/nciu.h
+++ b/modules/ca/src/client/nciu.h
@@ -183,6 +183,8 @@ public:
     unsigned getHostName (
         epicsGuard < epicsMutex > &,
         char * pBuf, unsigned bufLen ) const throw ();
+    unsigned getHostMinorProtocol (
+        epicsGuard < epicsMutex > &) const throw ();
     void writeException (
         epicsGuard < epicsMutex > &, epicsGuard < epicsMutex > &,
         int status, const char *pContext, unsigned type, arrayElementCount count );
diff --git a/modules/ca/src/client/netiiu.cpp b/modules/ca/src/client/netiiu.cpp
index c73732af6..04a5fb524 100644
--- a/modules/ca/src/client/netiiu.cpp
+++ b/modules/ca/src/client/netiiu.cpp
@@ -116,6 +116,12 @@ const char * netiiu::pHostName (
     return pHostNameNetIIU;
 }
 
+unsigned netiiu::getHostMinorProtocol ( 
+    epicsGuard < epicsMutex > & ) const throw ()
+{
+  return CA_UKN_MINOR_VERSION;
+}
+
 osiSockAddr netiiu::getNetworkAddress (
     epicsGuard < epicsMutex > & ) const
 {
diff --git a/modules/ca/src/client/netiiu.h b/modules/ca/src/client/netiiu.h
index 298337bd3..d21ed8428 100644
--- a/modules/ca/src/client/netiiu.h
+++ b/modules/ca/src/client/netiiu.h
@@ -43,6 +43,8 @@ public:
         unsigned bufLength ) const throw () = 0;
     virtual const char * pHostName (
         epicsGuard < epicsMutex > & ) const throw () = 0;
+    virtual unsigned getHostMinorProtocol ( 
+        epicsGuard < epicsMutex > & ) const throw ();
     virtual bool ca_v41_ok (
         epicsGuard < epicsMutex > & ) const = 0;
     virtual bool ca_v42_ok (
diff --git a/modules/ca/src/client/oldAccess.h b/modules/ca/src/client/oldAccess.h
index 2c39d2768..3e8edb914 100644
--- a/modules/ca/src/client/oldAccess.h
+++ b/modules/ca/src/client/oldAccess.h
@@ -64,6 +64,8 @@ public:
         chid pChan, char * pBuf, unsigned bufLength );
     friend const char * epicsStdCall ca_host_name (
         chid pChan );
+    friend unsigned epicsStdCall ca_host_minor_protocol (
+        chid pChan );
     friend const char * epicsStdCall ca_name (
         chid pChan );
     friend void epicsStdCall ca_set_puser (
diff --git a/modules/ca/src/client/oldChannelNotify.cpp b/modules/ca/src/client/oldChannelNotify.cpp
index 71688c94c..0a3512827 100644
--- a/modules/ca/src/client/oldChannelNotify.cpp
+++ b/modules/ca/src/client/oldChannelNotify.cpp
@@ -193,6 +193,16 @@ const char * epicsStdCall ca_host_name (
     return pChan->io.pHostName ( guard );
 }
 
+/*
+ * ca_host_minorProtocol ()
+ */
+unsigned epicsStdCall ca_host_minor_protocol (
+    chid pChan )
+{
+    epicsGuard < epicsMutex > guard ( pChan->cacCtx.mutexRef () );
+    return pChan->io.getHostMinorProtocol( guard );
+}
+
 /*
  * ca_set_puser ()
  */
diff --git a/modules/ca/src/client/tcpiiu.cpp b/modules/ca/src/client/tcpiiu.cpp
index 30f6fad17..b8ebaac32 100644
--- a/modules/ca/src/client/tcpiiu.cpp
+++ b/modules/ca/src/client/tcpiiu.cpp
@@ -1804,6 +1804,13 @@ const char * tcpiiu::pHostName (
     return this->hostNameCacheInstance.pointer ();
 }
 
+unsigned tcpiiu::getHostMinorProtocol ( 
+    epicsGuard < epicsMutex > & guard) const throw ()
+{   
+    guard.assertIdenticalMutex ( this->mutex );
+    return this->minorProtocolVersion;
+}
+
 void tcpiiu::disconnectAllChannels (
     epicsGuard < epicsMutex > & cbGuard,
     epicsGuard < epicsMutex > & guard,
diff --git a/modules/ca/src/client/udpiiu.cpp b/modules/ca/src/client/udpiiu.cpp
index d36e2c5b4..bfe3d628e 100644
--- a/modules/ca/src/client/udpiiu.cpp
+++ b/modules/ca/src/client/udpiiu.cpp
@@ -1342,6 +1342,12 @@ const char * udpiiu::pHostName (
     return netiiu::pHostName ( cacGuard );
 }
 
+unsigned udpiiu::getHostMinorProtocol ( 
+    epicsGuard < epicsMutex > & cacGuard ) const throw ()
+{
+    return netiiu::getHostMinorProtocol ( cacGuard );
+}
+
 bool udpiiu::ca_v42_ok (
     epicsGuard < epicsMutex > & cacGuard ) const
 {
diff --git a/modules/ca/src/client/udpiiu.h b/modules/ca/src/client/udpiiu.h
index aba79be5d..abc3fa757 100644
--- a/modules/ca/src/client/udpiiu.h
+++ b/modules/ca/src/client/udpiiu.h
@@ -239,7 +239,9 @@ private:
         unsigned bufLength ) const throw ();
     const char * pHostName (
         epicsGuard < epicsMutex > & ) const throw ();
-        bool ca_v41_ok (
+    unsigned getHostMinorProtocol ( 
+        epicsGuard < epicsMutex > & ) const throw ();
+    bool ca_v41_ok (
         epicsGuard < epicsMutex > & ) const;
     bool ca_v42_ok (
         epicsGuard < epicsMutex > & ) const;
diff --git a/modules/ca/src/client/virtualCircuit.h b/modules/ca/src/client/virtualCircuit.h
index 42af12f5f..0f43ea95e 100644
--- a/modules/ca/src/client/virtualCircuit.h
+++ b/modules/ca/src/client/virtualCircuit.h
@@ -168,6 +168,8 @@ public:
     unsigned getHostName (
         epicsGuard < epicsMutex > &,
         char *pBuf, unsigned bufLength ) const throw ();
+    unsigned getHostMinorProtocol ( 
+        epicsGuard < epicsMutex > &) const throw ();
     bool alive (
         epicsGuard < epicsMutex > & ) const;
     bool connecting (