1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
|
PSIM NETWORKING HOWTO
=====================
IMPLEMENTATION INFORMATION
1) NIC hardware emulation.
In order to simulate networking the simulator (PSIM in our case)
has to emulate some networking hardware.
At the time of this writing (2009/09 - gdb-6.8) no such emulation
is available.
However, a patch has been created which adds this functionality
to PSIM (see diff in this directory). Unfortunately, implementing
a network chip (or some other sort of 'data-source') in PSIM is
not quite that simple since PSIM is at the end of the day a single-
threaded, monolithic application which has no built-in support for
external asynchronous events (e.g., NIC packet reception or a
character arriving at a UART [the PSIM BSP uses a polled console
driver]).
In order to add such asynchronous support, the 'async_io' module
was added to PSIM. 'async_io' uses OS-support in the form of
a signal (SIGIO) that the OS sends to the PSIM process when I/O
becomes possible. The signal handler then executes a callback
which e.g., may schedule a PSIM interrupt.
However, the use of SIGIO and the O_ASYNC fcntl-flag is not portable
(BSD and linux only).
The 'ethtap' NIC emulation uses another not quite portable OS
service -- the host OS' TUN/TAP device which is some sort of
pipe with a networking-interface on one end and a file-system
interface on the other. The 'ethtap' NIC reads/writes packets
to the file-system interface and they then become available
to the host OS' networking.
This ascii-art shows how a RTEMS application inside PSIM can
communicate with an application on the host with both using
sockets. (If the host sets up proper routing table entries
then the RTEMS APP can even communicate with the internet...)
RTEMS APP HOST APP
| |
............. ............
. <socket> . .<socket> .
.RTEMS BSD . . HOST OS .
.networking . .networking.
............. ............
....................... .....................
.RTEMS BSD IF "ifsim1". . HOST OS IF: "tap0".
.e.g., 10.0.0.100 . . e.g., 10.0.0.1 .
....................... .....................
o
............. o
.RTEMS ifsim. o
. driver . o
............. o
|| o
|| o
--------------- o
ethtap o
hw emulation o
--------------- o
^ o
| o
-----> /dev/net/tun (special file on host OS) ooo
2) Device-tree. Once PSIM supports the 'ethtap' device then it
must be added to the device tree. The following properties are
relevant (The register addresses must match with what the
BSP/if_sim expects):
#### ETHTAP @ 0x0c100020 for 0x40
#
/ethtap@0x0c100020/reg 0x0c100020 0x40
# route interrupt to open-pic
/ethtap@0x0c100020 > 0 irq0 /opic@0x0c130000
# 'tun' device on host
/ethtap@0x0c100020/tun-device "/dev/net/tun"
# name of 'tap' device to use
/ethtap@0x0c100020/tap-ifname "tap0"
# ethernet address of simulated IF
/ethtap@0x0c100020/hw-address "00:00:00:22:11:00"
# generate CRC and append to received packet before
# handing over to the simulation. This is mostly for
# debugging the rtems device driver. If unsure, leave 'false'.
/ethtap@0x0c100020/enable-crc false
The 'tun-device' and 'tap-ifname' properties allow you to
configure the name of the special-file and the 'tap' interface
on the host.
3) RTEMS driver. The 'if_sim' driver implements a driver for
the 'ethtap' device.
USAGE INFORMATION
1) Configure application for networking; the
RTEMS_BSP_NETWORK_DRIVER_NAME is "ifsim1"
and
RTEMS_BSP_NETWORK_DRIVER_ATTACH is rtems_ifsim_attach
2) Patch, configure (--target=powerpc-rtems) and build
gdb-6.8. As already mentioned, the NIC emulation only
is available if your host-os is linux.
3) Create a 'device-tree' file. The BSP build process produces
a shell-script 'psim' residing in
<bsp_installdir>/powerpc-rtems/psim/tests/
which can be used for generating a device-tree file.
Call 'psim -d -n <application>'. The '-n' option adds the
emulated interface (the lines above) to the device tree.
The resulting file is saved as <application>.device.
The 'psim' script can also be used to launch an application
directly -- just omit the '-d' option.
4) Linux host network configuration:
Create a 'permanent' 'tap' interface. This allows you
to use 'psim' w/o special privileges (the 'tunctl' command
still must be executed by the super-user).
sudo tunctl -u <uid-of-user-running-psim>
You now can configure the 'tap0' interface:
sudo ifconfig tap0 10.0.0.1 up
and e.g., run a BOOTP server to provide RTEMS with its
network configuration:
sudo dhcpd3 -d tap0
Assuming that BOOTP gives the RTEMS guest an IP address
e.g., '10.0.0.100' you can 'ping' the RTEMS guest
from the linux host:
ping 10.0.0.100
|
