Introduced SCM_CREDENTIALS / SCM_CREDS in the socket control msgs.

auto/make

@@ -59,6 +59,7 @@ $echo >> $NXT_MAKEFILE
 $echo "NXT_LIB_UNIT_OBJS = \\" >> $NXT_MAKEFILE
 $echo "	$NXT_BUILD_DIR/src/nxt_lvlhsh.o \\" >> $NXT_MAKEFILE
 $echo "	$NXT_BUILD_DIR/src/nxt_murmur_hash.o \\" >> $NXT_MAKEFILE
+$echo "	$NXT_BUILD_DIR/src/nxt_socket_msg.o \\" >> $NXT_MAKEFILE
 $echo "	$NXT_BUILD_DIR/src/nxt_websocket.o \\" >> $NXT_MAKEFILE
 
 for nxt_src in $NXT_LIB_UNIT_SRCS

auto/sockets

@@ -158,6 +158,58 @@ nxt_feature_test="#include <stdio.h>
                   }"
 . auto/feature
 
+if [ $nxt_found = no ]; then
+    $echo
+    $echo $0: error: no msghdr.msg_control struct member.
+    $echo
+    exit 1;
+fi
+
+
+nxt_feature="sockopt SO_PASSCRED"
+nxt_feature_name=NXT_HAVE_SOCKOPT_SO_PASSCRED
+nxt_feature_run=
+nxt_feature_incs=
+nxt_feature_libs=
+nxt_feature_test="#define _GNU_SOURCE
+                  #include <sys/socket.h>
+
+                  int main() {
+                      return SO_PASSCRED == 0;
+                  }"
+. auto/feature
+
+
+if [ $nxt_found = yes ]; then
+    nxt_feature="struct ucred"
+    nxt_feature_name=NXT_HAVE_UCRED
+    nxt_feature_run=
+    nxt_feature_incs=
+    nxt_feature_libs=
+    nxt_feature_test="#define _GNU_SOURCE
+                      #include <sys/socket.h>
+                      #include <sys/un.h>
+
+                      int main() {
+                          return sizeof(struct ucred);
+                      }"
+    . auto/feature
+fi
+
+
+nxt_feature="struct cmsgcred"
+nxt_feature_name=NXT_HAVE_MSGHDR_CMSGCRED
+nxt_feature_run=
+nxt_feature_incs=
+nxt_feature_libs=
+nxt_feature_test="#define _GNU_SOURCE
+                  #include <sys/socket.h>
+
+                  int main() {
+                      return sizeof(struct cmsgcred);
+                  }"
+. auto/feature
+
 
 nxt_feature="sys/filio.h"
 nxt_feature_name=NXT_HAVE_SYS_FILIO_H

auto/sources

@@ -13,6 +13,7 @@ NXT_LIB_SRCS=" \
     src/nxt_mem_map.c \
     src/nxt_socket.c \
     src/nxt_socketpair.c \
+    src/nxt_socket_msg.c \
     src/nxt_credential.c \
     src/nxt_isolation.c \
     src/nxt_process.c \