1LIBSDP - A User Level Socket Switch for Seemless Migration to SDP 2----------------------------------------------------------------- 3 4OVERVIEW: 5--------- 6libsdp is a LD_PRELOAD-able library that can be used to migrate existing 7applications use InfiniBand Sockets Direct Protocol (SDP) instead of 8TCP sockets, transparently and without recompilations. To setup libsdp 9please follow the instructions below. 10 11SETUP: 12------ 13libsdp.so isn't setup automatically. it can be used in one of 2 ways: 141) LD_PRELOAD environment variable. Setting this to the name of the 15 library you want to use will cause it to be preloaded. 162) Adding the name of the library into /etc/ld.so.preload. This will 17 cause the library to be preloaded for every executable that is linked 18 with libc. 19 20The library should be installed in a directory in which the dynamic loader 21searches for shared libraries (as specified by LD_LIBRARY_PATH, 22/etc/ld.so.conf, etc). Alternatively, you can specify the full path to the 23library that you want to use in LD_PRELOAD or /etc/ld.so.preload as described 24above. 25 26The last option cant be used if you have multiple library versions 27(e.g. 64/32 bit) and want the linker to select between them automatically. 28The best way to handle such case is to use LD_LIBRARY_PATH to point to both the 29lib (the 32 bit version) and lib64 directories and LD_RELOAD the libsdp.so. 30This way the correct 32/64bit libsdp.so will be selected. 31For example running ssh over SDP with OFED distribution from bash this can be written: 32LD_LIBRARY_PATH=/usr/local/ofed/lib64:/usr/local/ofed/lib LD_PRELOAD=libsdp.so ssh 33 34CONFIGURATION: 35-------------- 36libsdp supports two modes of configuration: 37* simple operation where it converts all calls to socket(2) with a family 38 of AF_INET(6) and a type of SOCK_STREAM into family of AF_INET_SDP. 39* selective mode where it uses a configuration file to select which sockets 40 will be using SDP and which will not. 41 42For real world applications where communication with X, authentication, 43DNS and other servers connected through TCP is required the selective mode 44is required. 45 46Simple mode will be selected in one of the following conditions: 47* the environment variable SIMPLE_LIBSDP to a non-empty value 48* no configuration file is defined or is un-readble 49* the configuration file does not include any address family rule 50 51For information on how to configure libsdp, see libsdp.conf, which is installed 52in $(sysconfdir) (usually /usr/local/etc or /etc). The user can further control 53the file to be used for configuration by setting the environment variable: 54LIBSDP_CONFIG_FILE 55 56LIMITATIONS: 57------------ 581. Applications statically linked with libc will not allow dynamic pre-loading 59 to port these applications to use SDP one needs to replace specific socket 60 calls (within the application) with AF_INET_SDP and recompile. 612. If for some reason the dynamic linker fail to pre-load libc before the 62 libsdp.so is initialized or it does not support RTDL_NEXT, libsdp will 63 fail to find the libc socket API. To overcome this situation a simple 64 implementation of hijacking "socket" call is provided in libsdp_sys. 65 This partial implementation does not support any configuration and is 66 limited to i386 architecture. 673. Non-blocking connect in "both" mode defaults to SDP. Specific rules might be 68 needed for applications to operate properly. 69