The manpage systemd.exec implies that specifying a TCPWrapName uses
/etc/hosts.{allow,deny} in the same way as tcpd(8). However, this is not the
case: when /etc/hosts.allow is used for setting environment variables, these
variables are not handed over to the executed program.

---Example env.socket---
[Unit]
Description=Network socket for incoming env connections

[Install]
WantedBy=sockets.target

[Socket]
ListenStream=13131
Accept=true
---/Example---

---Example env@.service---
[Unit]
Description=test daemon
After=local-fs.target

[Service]
Environment=PATH=/bin:/usr/bin:/sbin:/usr/sbin
WorkingDirectory=/tmp
#ExecStart=@/usr/sbin/tcpd /usr/bin/env
ExecStart=/usr/bin/env

StandardInput=socket
StandardOutput=inherit
StandardError=syslog

TCPWrapName=env
---/Example---

---Example /etc/hosts.allow---
env : 127.0.0.1 : setenv TEST working
---/Example---

Steps to Reproduce:
1. Create env.socket, env@.service and /etc/hosts.allow as above
2. netcat 127.0.0.1 13131

Actual Results:  
The output does not contain "TEST=working"

Expected Results:  
The expected result can be seen by activating the out-commented ExecStart line
in env@.service: the output contains the line
TEST=working

As can be seen by the example, explicitly running /usr/sbin/tcpd in ExecStart
is an (ugly) workaround for the problem.