From 478afd5eb545d5ae0ecbfc2c9f216111f559fefe Mon Sep 17 00:00:00 2001
From: Philipp Gesang <philipp.gesang@intra2net.com>
Date: Wed, 5 Jan 2022 16:38:15 +0100
Subject: [PATCH] add session handling

The ``daemonize()`` API does not establish a new session so
processes that use it end up being controlled by the tty of the
process they were launched under, which too often happens to be
some system console.
---
 src/daemonfunc.cpp |   27 +++++++++++++++++++++++++++
 src/daemonfunc.hpp |    2 ++
 2 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/src/daemonfunc.cpp b/src/daemonfunc.cpp
index 248a79b..6481493 100644
--- a/src/daemonfunc.cpp
+++ b/src/daemonfunc.cpp
@@ -25,6 +25,8 @@ on this file might be covered by the GNU General Public License.
 #include <stdlib.h>
 #include <pwd.h>
 #include <grp.h>
+#include <errno.h>
+#include <string.h>
 
 #include <string>
 #include <stdexcept>
@@ -227,5 +229,30 @@ bool pid_of(const std::string& name, std::vector< pid_t >& result)
    return true;
 } // eo pidOf(const std::string&,std::vector< pid_t >&)
 
+/**
+ * @brief   establish a new session for the current process.
+ *
+ * @return  the id of the new session.
+ *
+ * This wraps setsid(2); to be called from a child process after forking.
+ * Raises ``runtime_error`` if the call fails.
+ */
+pid_t create_session (void)
+{
+    pid_t sid;
+
+    errno = 0;
+    if ((sid = setsid ()) == -1)
+    {
+        throw std::runtime_error
+            ((std::string)
+             "create_session: setsid() returned an error ("
+             + I2n::to_string (errno)
+             + "): " + strerror (errno));
+    }
+
+    return sid;
+}
+
 }
 }
diff --git a/src/daemonfunc.hpp b/src/daemonfunc.hpp
index f6f77a3..f5b85cf 100644
--- a/src/daemonfunc.hpp
+++ b/src/daemonfunc.hpp
@@ -38,6 +38,8 @@ bool drop_root_privileges(const std::string &username,
                           const std::string &group, bool get_group_from_user=false);
 
 bool pid_of(const std::string& name, std::vector< pid_t >& result);
+
+pid_t create_session (void);
 }
 }
 
-- 
1.7.1