1219820SjeffLIBSDP - A User Level Socket Switch for Seemless Migration to SDP 2219820Sjeff----------------------------------------------------------------- 3219820Sjeff 4219820SjeffOVERVIEW: 5219820Sjeff--------- 6219820Sjefflibsdp is a LD_PRELOAD-able library that can be used to migrate existing 7219820Sjeffapplications use InfiniBand Sockets Direct Protocol (SDP) instead of 8219820SjeffTCP sockets, transparently and without recompilations. To setup libsdp 9219820Sjeffplease follow the instructions below. 10219820Sjeff 11219820SjeffSETUP: 12219820Sjeff------ 13219820Sjefflibsdp.so isn't setup automatically. it can be used in one of 2 ways: 14219820Sjeff1) LD_PRELOAD environment variable. Setting this to the name of the 15219820Sjeff library you want to use will cause it to be preloaded. 16219820Sjeff2) Adding the name of the library into /etc/ld.so.preload. This will 17219820Sjeff cause the library to be preloaded for every executable that is linked 18219820Sjeff with libc. 19219820Sjeff 20219820SjeffThe library should be installed in a directory in which the dynamic loader 21219820Sjeffsearches for shared libraries (as specified by LD_LIBRARY_PATH, 22219820Sjeff/etc/ld.so.conf, etc). Alternatively, you can specify the full path to the 23219820Sjefflibrary that you want to use in LD_PRELOAD or /etc/ld.so.preload as described 24219820Sjeffabove. 25219820Sjeff 26219820SjeffThe last option cant be used if you have multiple library versions 27219820Sjeff(e.g. 64/32 bit) and want the linker to select between them automatically. 28219820SjeffThe best way to handle such case is to use LD_LIBRARY_PATH to point to both the 29219820Sjefflib (the 32 bit version) and lib64 directories and LD_RELOAD the libsdp.so. 30219820SjeffThis way the correct 32/64bit libsdp.so will be selected. 31219820SjeffFor example running ssh over SDP with OFED distribution from bash this can be written: 32219820SjeffLD_LIBRARY_PATH=/usr/local/ofed/lib64:/usr/local/ofed/lib LD_PRELOAD=libsdp.so ssh 33219820Sjeff 34219820SjeffCONFIGURATION: 35219820Sjeff-------------- 36219820Sjefflibsdp supports two modes of configuration: 37219820Sjeff* simple operation where it converts all calls to socket(2) with a family 38219820Sjeff of AF_INET(6) and a type of SOCK_STREAM into family of AF_INET_SDP. 39219820Sjeff* selective mode where it uses a configuration file to select which sockets 40219820Sjeff will be using SDP and which will not. 41219820Sjeff 42219820SjeffFor real world applications where communication with X, authentication, 43219820SjeffDNS and other servers connected through TCP is required the selective mode 44219820Sjeffis required. 45219820Sjeff 46219820SjeffSimple mode will be selected in one of the following conditions: 47219820Sjeff* the environment variable SIMPLE_LIBSDP to a non-empty value 48219820Sjeff* no configuration file is defined or is un-readble 49219820Sjeff* the configuration file does not include any address family rule 50219820Sjeff 51219820SjeffFor information on how to configure libsdp, see libsdp.conf, which is installed 52219820Sjeffin $(sysconfdir) (usually /usr/local/etc or /etc). The user can further control 53219820Sjeffthe file to be used for configuration by setting the environment variable: 54219820SjeffLIBSDP_CONFIG_FILE 55219820Sjeff 56219820SjeffLIMITATIONS: 57219820Sjeff------------ 58219820Sjeff1. Applications statically linked with libc will not allow dynamic pre-loading 59219820Sjeff to port these applications to use SDP one needs to replace specific socket 60219820Sjeff calls (within the application) with AF_INET_SDP and recompile. 61219820Sjeff2. If for some reason the dynamic linker fail to pre-load libc before the 62219820Sjeff libsdp.so is initialized or it does not support RTDL_NEXT, libsdp will 63219820Sjeff fail to find the libc socket API. To overcome this situation a simple 64219820Sjeff implementation of hijacking "socket" call is provided in libsdp_sys. 65219820Sjeff This partial implementation does not support any configuration and is 66219820Sjeff limited to i386 architecture. 67219820Sjeff3. Non-blocking connect in "both" mode defaults to SDP. Specific rules might be 68219820Sjeff needed for applications to operate properly. 69