.\" $NetBSD: rumpclient.3,v 1.3 2013/03/08 08:30:44 wiz Exp $ .\" .\" Copyright (c) 2011 Antti Kantee. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .Dd February 16, 2011 .Dt RUMPCLIENT 3 .Os .Sh NAME .Nm rumpclient .Nd rump client library .Sh LIBRARY .Lb rumpclient .Sh SYNOPSIS .In rump/rumpclient.h .In rump/rump_syscalls.h .Ft int .Fn rumpclient_init .Ft pid_t .Fn rumpclient_fork .Ft pid_t .Fn rumpclient_vfork .Ft struct rumpclient_fork * .Fn rumpclient_prefork .Ft int .Fn rumpclient_fork_init "struct rumpclient_fork *rfp" .Ft void .Fn rumpclient_fork_cancel "struct rumpclient_fork *rfp" .Ft int .Fn rumpclient_exec "const char *path" "char *const argv[]" "char *const envp[]" .Ft int .Fn rumpclient_daemon "int nochdir" "int noclose" .Ft void .Fn rumpclient_setconnretry "time_t retrytime" .Ft int .Fo rumpclient_syscall .Fa "int num" "const void *sysarg" "size_t argsize" "register_t *retval" .Fc .Sh DESCRIPTION .Nm is the clientside implementation of the .Xr rump_sp 7 facility. It can be used to connect to a rump kernel server and make system call style requests. .Pp Every connection to a rump kernel server creates a new process context in the rump kernel. By default a process is inherited from init, but through existing connections and the forking facility offered by .Nm it is possible to form process trees. .Bl -tag -width xxxx .It Fn rumpclient_init Initialize .Nm . The server address is determined from the environment variable .Ev RUMP_SERVER according to syntax described in .Xr rump_sp 7 . The new process is registered to the rump kernel with the command name from .Xr getprogname 3 . .It Fn rumpclient_fork Fork a rump client process. This also causes a host process fork via .Xr fork 2 . The child will have a copy of the parent's rump kernel file descriptors. .It Fn rumpclient_vfork Like above, but the host uses .Xr vfork 2 . .It Fn rumpclient_prefork Low-level routine which instructs the rump kernel that the current process is planning to fork. The routine returns a .Pf non- Dv NULL cookie if successful. .It Fn rumpclient_fork_init rfp Low-level routine which works like .Fn rumpclient_init , with the exception that it uses the .Ar rfp context created by a call to .Fn rumpclient_prefork . This is typically called from the child of a .Xr fork 2 call. .It Fn rumpclient_fork_cancel rfp Cancel previously initiated prefork context. This is useful for error handling in case a full fork could not be carried through. .It Fn rumpclient_exec path argv envp This call is a .Nm wrapper around .Xr execve 2 . The wrapper makes sure that the rump kernel process context stays the same in the newly executed program. This means that the rump kernel PID remains the same and the same rump file descriptors are available (apart from ones which were marked with .Dv FD_CLOEXEC ) . .Pp It should be noted that the newly executed program must call .Fn rumpclient_init before any other rump kernel communication can take place. The wrapper cannot do it because it no longer has program control. However, since all rump clients call the init routine, this should not be a problem. .It Fn rumpclient_daemon noclose nochdir This function performs the equivalent of .Xr daemon 3 , but also ensures that the internal call to .Xr fork 2 is handled properly. This routine is provided for convenience. .It Fn rumpclient_setconnretry retrytime Set the timeout for how long the client attempts to reconnect to the server in case of a broken connection. After the timeout expires the client will return a failure for that particular request. It is critical to note that after a restablished connection the rump kernel context will be that of a newly connected client. This means all previous kernel state such as file descriptors will be lost. It is largely up to a particular application if this has impact or not. For example, web browsers tend to recover fairly smoothly from a kernel server reconnect, while .Xr sshd 8 gets confused if its sockets go missing. .Pp If .Ar retrytime is a positive integer, it means the number of seconds for which reconnection will be attempted. The value 0 means that reconnection will not be attempted, and all subsequent operations will return the errno .Er ENOTCONN . .Pp Additionally, the following special values are accepted: .Bl -tag -width xxxx .It Dv RUMPCLIENT_RETRYCONN_INFTIME Attempt reconnection indefinitely. .It Dv RUMPCLIENT_RETRYCONN_ONCE Attempt reconnect exactly once. What this precisely means depends on the situation: e.g. getting .Er EHOSTUNREACH immediately or the TCP connection request timeouting are considered to be one retry. .It Dv RUMPCLIENT_RETRYCONN_DIE In case of a broken connection is detected at runtime, call .Xr exit 3 . This is useful for example in testing. It ensures that clients are killed immediately when they attempt to communicate with a halted server. .El .It Fn rumpclient_syscall num sysarg argsize retval Execute an "indirect" system call. In the normal case system calls are executed through the interfaces in .In rump/rump_syscalls.h (for example .Fn rump_sys_read fd buf nbytes ) . This interface allows calling the server with pre-marshalled arguments. .El .Pp Additionally, all of the supported rump system calls are available through this library. See .In rump/rump_syscalls.h for a list. .Sh RETURN VALUES .Nm routines return \-1 in case of error and set errno. In case of success a non-negative integer is returned, where applicable. .Sh SEE ALSO .Xr rump_server 1 , .Xr rump 3 , .Xr rump_sp 7 .Sh CAVEATS Interfaces for a cryptographically authenticated client-server handshake do not currently exist. This can be worked around with e.g. host access control and an ssh tunnel.