9 socket_wrapper - A library passing all socket communications through unix sockets.
14 LD_PRELOAD=libsocket_wrapper.so SOCKET_WRAPPER_DIR=/tmp/tmp.bQRELqDrhM SOCKET_WRAPPER_DEFAULT_IFACE=10 *./myapplication*
19 socket_wrapper aims to help client/server software development teams willing to
20 gain full functional test coverage. It makes possible to run several instances
21 of the full software stack on the same machine and perform locally functional
22 testing of complex network configurations.
24 - Redirects all network communication to happen over Unix sockets.
25 - Support for IPv4 and IPv6 socket and addressing emulation.
26 - Ability to capture network traffic in pcap format.
27 - Passing IP sockets (up to 6) via SCM_RIGHTS is supported,
28 but pcap support only works reliable if the socket is used
29 by a single process at a time.
34 *SOCKET_WRAPPER_DIR*::
36 The user defines a directory where to put all the unix sockets using the
37 environment variable "SOCKET_WRAPPER_DIR=/path/to/socket_dir". When a server
38 opens a port or a client wants to connect, socket_wrapper will translate IP
39 addresses to a special socket_wrapper name and look for the relevant Unix
40 socket in the SOCKET_WRAPPER_DIR.
42 *SOCKET_WRAPPER_IPV4_NETWORK*::
44 By default the loopback IPv4 network "127.0.0.0/8" and the
45 "127.0.0.x" can be used. In order to make more realistic testing
46 possible it is possible to use the "10.0.0.0/8" IPv4 network instead.
47 But note within "10.0.0.0/8" only "10.53.57.<ID>" can be used,
48 but the broadcast address is "10.255.255.255".
49 The following two value are allowed:
50 SOCKET_WRAPPER_IPV4_NETWORK="127.0.0.0" (the default) and
51 SOCKET_WRAPPER_IPV4_NETWORK="10.53.57.0".
53 *SOCKET_WRAPPER_DEFAULT_IFACE*::
55 Additionally, the default interface to be used by an application is defined with
56 "SOCKET_WRAPPER_DEFAULT_IFACE=<ID>" where the valid range for <ID> starts with 1
57 (the default) and ends with 64. This is analogous to use the IPv4 addresses
58 "127.0.0.<ID>"/"10.53.57.<ID>" or IPv6 addresses "fd00::5357:5f<IDx>" (where
59 <IDx> is a hexadecimal presentation of <ID>). You should always set the default
60 interface. If you listen on INADDR_ANY then it will use the default interface to
63 *SOCKET_WRAPPER_PCAP_FILE*::
65 When debugging, it is often interesting to investigate the network traffic
66 between the client and server within your application. If you define
67 SOCKET_WRAPPER_PCAP_FILE=/path/to/file.pcap, socket_wrapper will dump all your
68 network traffic to the specified file. After the test has been finished you're
69 able to open the file for example with Wireshark.
71 *SOCKET_WRAPPER_MTU*::
73 With this variable you can change the MTU size. However we do not recomment to
74 do that as the default size of 1500 byte is best for formatting PCAP files.
76 The minimum value you can set is 512 and the maximum 32768.
78 *SOCKET_WRAPPER_MAX_SOCKETS*::
80 This variable can be used to set the maximum number of sockets to be used by
83 The default value is set to 65535 and the maximum 256000.
85 *SOCKET_WRAPPER_DEBUGLEVEL*::
87 If you need to see what is going on in socket_wrapper itself or try to find a
88 bug, you can enable logging support in socket_wrapper if you built it with
96 *SOCKET_WRAPPER_DISABLE_DEEPBIND*::
98 This allows you to disable deep binding in socket_wrapper. This is useful for
99 running valgrind tools or sanitizers like (address, undefined, thread).
101 *SOCKET_WRAPPER_DIR_ALLOW_ORIG*::
103 SOCKET_WRAPPER_DIR is resolved by socket_wrapper using realpath(3).
104 Given that Unix sockets are constructed relative to this directory,
105 the resulting path can sometimes be too long to allow valid socket
106 paths to be constructed due to length restrictions. Setting this
107 variable (to any value) allows socket_wrapper to fall back to the
108 original value of SOCKET_WRAPPER_DIR if realpath(3) makes it too long
114 # Open a console and create a directory for the unix sockets.
118 # Then start nc to listen for network traffic using the temporary directory.
119 $ LD_PRELOAD=libsocket_wrapper.so \
120 SOCKET_WRAPPER_DIR=/tmp/tmp.bQRELqDrhM \
121 SOCKET_WRAPPER_DEFAULT_IFACE=10 nc -v -l 127.0.0.10 7
123 # (If nc, listens on 0.0.0.0 then listener will be open on 127.0.0.10 because
124 # it is the default interface)
126 # Now open another console and start 'nc' as a client to connect to the server:
127 $ LD_PRELOAD=libsocket_wrapper.so \
128 SOCKET_WRAPPER_DIR=/tmp/tmp.bQRELqDrhM \
129 SOCKET_WRAPPER_DEFAULT_IFACE=100 nc -v 127.0.0.10 7
131 # (The client will use the address 127.0.0.100 when connecting to the server)
132 # Now you can type 'Hello!' which will be sent to the server and should appear
133 # in the console output of the server.