Re: [patch 1/2][RFC] add socketat syscall

[Daniel Lezcano <dlezcano-NmTC/0ZBporQT0dZR+AlfA@public.gmane.org>]

Michael Kerrisk wrote:
>> On Fri, Oct 31, 2008 at 4:56 PM, Daniel Lezcano <dlezcano-NmTC/0ZBporQT0dZR+AlfA@public.gmane.org> wrote:
>>> This patch adds the socketat syscall which allows to specify in
>>> which network namespace we want to create a socket. The network
>>> namespace destination is referred by a socket fd previously opened
>>> in the destination network namespace.
> 
> Daniel,
> 
> Is there any documentation for this system call, and/or test programs?

Not yet.

This small patch is a proposition to Andreas and Vivien to have a single 
process being able to manage several network namespaces.

When a process unshares the network, it creates a socket which is used 
as a socket control (it belongs to the network namespace). Each time a 
network namespace is created, a socket control is created.

When the process has to create a socket for a specific network 
namespace, it can use the socket control to specify it. This is the 
purpose of the socketat syscall.

One example for a program in userspace:

int main(int argc, char *argv[])
{
	const int maxunshare = 128;
	int scs[maxunshare];
	int i, fd;
	
	for (i = 0; i < maxunshare; i++) {
		scs[i] = socket(PF_INET, SOCK_DGRAM, 0);
		unshare(CLONE_NEWNET);
	}

	....

	/* I want to create a socket inside the network namespace #10 */

	fd = socketat(scs[10], PF_INET, SOCKET_STREAM, 0);

	....

	bind, listen, etc ...
}

>>> Signed-off-by: Daniel Lezcano <dlezcano-NmTC/0ZBporQT0dZR+AlfA@public.gmane.org>
>>> ---
>>>  arch/x86/include/asm/unistd_32.h   |    1
>>>  arch/x86/include/asm/unistd_64.h   |    3 +-
>>>  arch/x86/kernel/syscall_table_32.S |    1
>>>  include/linux/syscalls.h           |    1
>>>  kernel/sys_ni.c                    |    1
>>>  net/socket.c                       |   45 +++++++++++++++++++++++++++++++++++++
>>>  6 files changed, 51 insertions(+), 1 deletion(-)
>>>
>>> Index: net-next-2.6/arch/x86/include/asm/unistd_32.h
>>> ===================================================================
>>> --- net-next-2.6.orig/arch/x86/include/asm/unistd_32.h
>>> +++ net-next-2.6/arch/x86/include/asm/unistd_32.h
>>> @@ -338,6 +338,7 @@
>>>  #define __NR_dup3              330
>>>  #define __NR_pipe2             331
>>>  #define __NR_inotify_init1     332
>>> +#define __NR_socketat           333
>>>
>>>  #ifdef __KERNEL__
>>>
>>> Index: net-next-2.6/arch/x86/include/asm/unistd_64.h
>>> ===================================================================
>>> --- net-next-2.6.orig/arch/x86/include/asm/unistd_64.h
>>> +++ net-next-2.6/arch/x86/include/asm/unistd_64.h
>>> @@ -653,7 +653,8 @@ __SYSCALL(__NR_dup3, sys_dup3)
>>>  __SYSCALL(__NR_pipe2, sys_pipe2)
>>>  #define __NR_inotify_init1                     294
>>>  __SYSCALL(__NR_inotify_init1, sys_inotify_init1)
>>> -
>>> +#define __NR_socketat                           295
>>> +__SYSCALL(__NR_socketat, sys_socketat)
>>>
>>>  #ifndef __NO_STUBS
>>>  #define __ARCH_WANT_OLD_READDIR
>>> Index: net-next-2.6/arch/x86/kernel/syscall_table_32.S
>>> ===================================================================
>>> --- net-next-2.6.orig/arch/x86/kernel/syscall_table_32.S
>>> +++ net-next-2.6/arch/x86/kernel/syscall_table_32.S
>>> @@ -332,3 +332,4 @@ ENTRY(sys_call_table)
>>>        .long sys_dup3                  /* 330 */
>>>        .long sys_pipe2
>>>        .long sys_inotify_init1
>>> +       .long sys_socketat
>>> Index: net-next-2.6/net/socket.c
>>> ===================================================================
>>> --- net-next-2.6.orig/net/socket.c
>>> +++ net-next-2.6/net/socket.c
>>> @@ -1253,6 +1253,51 @@ out_release:
>>>        return retval;
>>>  }
>>>
>>> +asmlinkage long sys_socketat(int fd, int family, int type, int protocol)
>>> +{
>>> +       int retval, fput_needed;
>>> +       struct socket *sock;
>>> +       struct socket *sockat;
>>> +       struct net *net;
>>> +       int flags;
>>> +
>>> +       /* Check the SOCK_* constants for consistency.  */
>>> +       BUILD_BUG_ON(SOCK_CLOEXEC != O_CLOEXEC);
>>> +       BUILD_BUG_ON((SOCK_MAX | SOCK_TYPE_MASK) != SOCK_TYPE_MASK);
>>> +       BUILD_BUG_ON(SOCK_CLOEXEC & SOCK_TYPE_MASK);
>>> +       BUILD_BUG_ON(SOCK_NONBLOCK & SOCK_TYPE_MASK);
>>> +
>>> +       flags = type & ~SOCK_TYPE_MASK;
>>> +       if (flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
>>> +               return -EINVAL;
>>> +       type &= SOCK_TYPE_MASK;
>>> +
>>> +       if (SOCK_NONBLOCK != O_NONBLOCK && (flags & SOCK_NONBLOCK))
>>> +               flags = (flags & ~SOCK_NONBLOCK) | O_NONBLOCK;
>>> +
>>> +       sock = sockfd_lookup_light(fd, &retval, &fput_needed);
>>> +       if (!sock)
>>> +               goto out;
>>> +
>>> +       net = sock_net(sock->sk);
>>> +
>>> +       retval = __sock_create(net, family, type, protocol, &sockat, 0);
>>> +       if (retval)
>>> +               goto out_fput;
>>> +
>>> +       retval = sock_map_fd(sock, flags & (O_CLOEXEC | O_NONBLOCK));
>>> +       if (retval < 0)
>>> +               goto out_release;
>>> +out_fput:
>>> +       fput_light(sock->file, fput_needed);
>>> +out:
>>> +       return retval;
>>> +
>>> +out_release:
>>> +       sock_release(sockat);
>>> +       goto out;
>>> +}
>>> +
>>>  /*
>>>  *     Create a pair of connected sockets.
>>>  */
>>> Index: net-next-2.6/include/linux/syscalls.h
>>> ===================================================================
>>> --- net-next-2.6.orig/include/linux/syscalls.h
>>> +++ net-next-2.6/include/linux/syscalls.h
>>> @@ -423,6 +423,7 @@ asmlinkage long sys_recvfrom(int, void _
>>>                                struct sockaddr __user *, int __user *);
>>>  asmlinkage long sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags);
>>>  asmlinkage long sys_socket(int, int, int);
>>> +asmlinkage long sys_socketat(int, int, int, int);
>>>  asmlinkage long sys_socketpair(int, int, int, int __user *);
>>>  asmlinkage long sys_socketcall(int call, unsigned long __user *args);
>>>  asmlinkage long sys_listen(int, int);
>>> Index: net-next-2.6/kernel/sys_ni.c
>>> ===================================================================
>>> --- net-next-2.6.orig/kernel/sys_ni.c
>>> +++ net-next-2.6/kernel/sys_ni.c
>>> @@ -40,6 +40,7 @@ cond_syscall(sys_send);
>>>  cond_syscall(sys_recvfrom);
>>>  cond_syscall(sys_recv);
>>>  cond_syscall(sys_socket);
>>> +cond_syscall(sys_socketat);
>>>  cond_syscall(sys_setsockopt);
>>>  cond_syscall(compat_sys_setsockopt);
>>>  cond_syscall(sys_getsockopt);
>>>
>>> --
>>> _______________________________________________
>>> Containers mailing list
>>> Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
>>> https://lists.linux-foundation.org/mailman/listinfo/containers
>>>
>>
>>
>> --
>> Michael Kerrisk Linux man-pages maintainer;
>> http://www.kernel.org/doc/man-pages/ Found a documentation bug?
>> http://www.kernel.org/doc/man-pages/reporting_bugs.html
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> 
> 
> 


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