Problem: No direct support for setting socket priority (#4118)

* Problem: No direct support for setting socket priority

Solution: Add ZMQ_PRIORITY socket option, which sets the
SO_PRIORITY socket option on the underlying socket. This
socket option is not supported under Windows. Check option
and set socket option on creation of underlying socket.

Author: aheroff1

CMakeLists.txt

@@ -723,6 +723,7 @@ if(NOT CMAKE_CROSSCOMPILING AND NOT MSVC)
   zmq_check_o_cloexec()
   zmq_check_so_bindtodevice()
   zmq_check_so_keepalive()
+  zmq_check_so_priority()
   zmq_check_tcp_keepcnt()
   zmq_check_tcp_keepidle()
   zmq_check_tcp_keepintvl()

RELICENSE/nokia.md

@@ -0,0 +1,13 @@
+# Permission to Relicense under MPLv2
+
+This is a statement by Nokia
+that grants permission to relicense its copyrights in the libzmq C++
+library (ZeroMQ) under the Mozilla Public License v2 (MPLv2).
+
+A portion of the commits made by the Github handle "aheroff1", with
+commit author "Andy Heroff", are copyright of Nokia.
+This document hereby grants the libzmq project team to relicense libzmq, 
+including all past, present and future contributions of the author listed above.
+
+Andy Heroff
+2021/01/05

acinclude.m4

@@ -870,6 +870,33 @@ int main (int argc, char *argv [])
     AS_IF([test "x$libzmq_cv_tcp_keepalive" = "xyes"], [$1], [$2])
 }])
 
+dnl ################################################################################
+dnl # LIBZMQ_CHECK_SO_PRIORITY([action-if-found], [action-if-not-found])           #
+dnl # Check if SO_PRIORITY is supported                                            #
+dnl ################################################################################
+AC_DEFUN([LIBZMQ_CHECK_SO_PRIORITY], [{
+    AC_CACHE_CHECK([whether SO_PRIORITY is supported], [libzmq_cv_so_priority],
+        [AC_TRY_RUN([/* SO_PRIORITY test */
+#include <sys/types.h>
+#include <sys/socket.h>
+
+int main (int argc, char *argv [])
+{
+    int s, rc, opt = 1;
+    return (
+        ((s = socket (PF_INET, SOCK_STREAM, 0)) == -1) ||
+        ((rc = setsockopt (s, SOL_SOCKET, SO_PRIORITY, (char*) &opt, sizeof (int))) == -1)
+    );
+}
+        ],
+        [libzmq_cv_so_priority="yes"],
+        [libzmq_cv_so_priority="no"],
+        [libzmq_cv_so_priority="not during cross-compile"]
+        )]
+    )
+    AS_IF([test "x$libzmq_cv_so_priority" = "xyes"], [$1], [$2])
+}])
+
 dnl ################################################################################
 dnl # LIBZMQ_CHECK_GETRANDOM([action-if-found], [action-if-not-found])  #
 dnl # Checks if getrandom is supported                                  #

builds/cmake/Modules/ZMQSourceRunChecks.cmake

@@ -311,3 +311,22 @@ int main(int argc, char *argv [])
 "
     ZMQ_HAVE_NOEXCEPT)
 endmacro()
+
+macro(zmq_check_so_priority)
+  message(STATUS "Checking whether SO_PRIORITY is supported")
+  check_c_source_runs(
+    "
+#include <sys/types.h>
+#include <sys/socket.h>
+
+int main (int argc, char *argv [])
+{
+    int s, rc, opt = 1;
+    return (
+        ((s = socket (PF_INET, SOCK_STREAM, 0)) == -1) ||
+        ((rc = setsockopt (s, SOL_SOCKET, SO_PRIORITY, (char*) &opt, sizeof (int))) == -1)
+    );
+}
+"
+    ZMQ_HAVE_SO_PRIORITY)
+endmacro()

builds/cmake/platform.hpp.in

@@ -40,6 +40,7 @@
 
 #cmakedefine ZMQ_HAVE_SOCK_CLOEXEC
 #cmakedefine ZMQ_HAVE_SO_KEEPALIVE
+#cmakedefine ZMQ_HAVE_SO_PRIORITY
 #cmakedefine ZMQ_HAVE_TCP_KEEPCNT
 #cmakedefine ZMQ_HAVE_TCP_KEEPIDLE
 #cmakedefine ZMQ_HAVE_TCP_KEEPINTVL

configure.ac

@@ -959,6 +959,12 @@ LIBZMQ_CHECK_TCP_KEEPALIVE([
         [Whether TCP_KEEPALIVE is supported.])
     ])
 
+LIBZMQ_CHECK_SO_PRIORITY([
+    AC_DEFINE([ZMQ_HAVE_SO_PRIORITY],
+        [1],
+        [Whether SO_PRIORITY is supported.])
+    ])
+
 LIBZMQ_CHECK_GETRANDOM([
     AC_DEFINE([ZMQ_HAVE_GETRANDOM],
         [1],

doc/zmq_getsockopt.txt

@@ -513,6 +513,18 @@ Default value:: -1
 Applicable socket types:: all bound sockets, when using IPC or TCP transport
 
 
+ZMQ_PRIORITY: Retrieve the Priority on socket
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Gets the protocol-defined priority for all packets to be sent on this
+socket, where supported by the OS.
+
+[horizontal]
+Option value type:: int
+Option value unit:: >0
+Default value:: 0
+Applicable socket types:: all, only for connection-oriented transports
+
+
 ZMQ_RATE: Retrieve multicast data rate
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_RATE' option shall retrieve the maximum send or receive data rate for

doc/zmq_setsockopt.txt

@@ -606,6 +606,19 @@ Default value:: -1
 Applicable socket types:: all bound sockets, when using IPC or TCP transport
 
 
+ZMQ_PRIORITY: Set the Priority on socket
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Sets the protocol-defined priority for all packets to be sent on this
+socket, where supported by the OS. In Linux, values greater than 6
+require admin capability (CAP_NET_ADMIN)
+
+[horizontal]
+Option value type:: int
+Option value unit:: >0
+Default value:: 0
+Applicable socket types:: all, only for connection-oriented transports
+
+
 ZMQ_PROBE_ROUTER: bootstrap connections to ROUTER sockets
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 When set to 1, the socket will automatically send an empty message when a

include/zmq.h

@@ -682,6 +682,7 @@ ZMQ_EXPORT void zmq_threadclose (void *thread_);
 #define ZMQ_RECONNECT_STOP 109
 #define ZMQ_HELLO_MSG 110
 #define ZMQ_DISCONNECT_MSG 111
+#define ZMQ_PRIORITY 112
 
 /*  DRAFT ZMQ_RECONNECT_STOP options                                          */
 #define ZMQ_RECONNECT_STOP_CONN_REFUSED 0x1

src/ip.cpp

@@ -230,6 +230,16 @@ void zmq::set_ip_type_of_service (fd_t s_, int iptos_)
 #endif
 }
 
+void zmq::set_socket_priority (fd_t s_, int priority_)
+{
+#ifdef ZMQ_HAVE_SO_PRIORITY
+    int rc =
+      setsockopt (s_, SOL_SOCKET, SO_PRIORITY,
+                  reinterpret_cast<char *> (&priority_), sizeof (priority_));
+    errno_assert (rc == 0);
+#endif
+}
+
 int zmq::set_nosigpipe (fd_t s_)
 {
 #ifdef SO_NOSIGPIPE