Home » Mailing lists » Devel » [RFC PATCH 0/5] net: socket bind to file descriptor introduced
| [RFC PATCH 0/5] net: socket bind to file descriptor introduced [message #47535] |
Wed, 15 August 2012 16:21  |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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This patch set introduces new socket operation and new system call:
sys_fbind(), which allows to bind socket to opened file.
File to bind to can be created by sys_mknod(S_IFSOCK) and opened by
open(O_PATH).
This system call is especially required for UNIX sockets, which has name
lenght limitation.
The following series implements...
---
Stanislav Kinsbursky (5):
net: cleanup unix_bind() a little
net: split unix_bind()
net: new protocol operation fbind() introduced
net: fbind() for unix sockets protocol operations introduced
syscall: sys_fbind() introduced
arch/x86/syscalls/syscall_32.tbl | 1
arch/x86/syscalls/syscall_64.tbl | 1
include/linux/net.h | 2 +
include/linux/syscalls.h | 1
kernel/sys_ni.c | 3 +
net/socket.c | 25 +++++++
net/unix/af_unix.c | 136 ++++++++++++++++++++++++++++++--------
7 files changed, 140 insertions(+), 29 deletions(-)
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| [RFC PATCH 2/5] net: split unix_bind() [message #47536 is a reply to message #47535] |
Wed, 15 August 2012 16:22  |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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This patch moves UNIX socket insert into separated function, because this code
will be used for unix_fbind() too.
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
net/unix/af_unix.c | 52 +++++++++++++++++++++++++++++-----------------------
1 files changed, 29 insertions(+), 23 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index bc90ddb..b26200d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -814,11 +814,38 @@ fail:
return NULL;
}
+static int __unix_add_sock(struct path *path, struct sock *sk,
+ struct unix_address *addr, int hash)
+{
+ struct net *net = sock_net(sk);
+ struct unix_sock *u = unix_sk(sk);
+ struct sockaddr_un *sunaddr = addr->name;
+ char *sun_path = sunaddr->sun_path;
+ struct hlist_head *list;
+
+ if (!sun_path[0]) {
+ if (__unix_find_socket_byname(net, sunaddr, addr->len,
+ sk->sk_type, hash)) {
+ unix_release_addr(addr);
+ return -EADDRINUSE;
+ }
+
+ list = &unix_socket_table[addr->hash];
+ } else {
+ list = &unix_socket_table[path->dentry->d_inode->i_ino & (UNIX_HASH_SIZE-1)];
+ u->path = *path;
+ }
+
+ __unix_remove_socket(sk);
+ u->addr = addr;
+ __unix_insert_socket(list, sk);
+ return 0;
+
+}
static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
struct sock *sk = sock->sk;
- struct net *net = sock_net(sk);
struct unix_sock *u = unix_sk(sk);
struct sockaddr_un *sunaddr = (struct sockaddr_un *)uaddr;
char *sun_path = sunaddr->sun_path;
@@ -827,7 +854,6 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
int err;
unsigned int hash;
struct unix_address *addr;
- struct hlist_head *list;
err = -EINVAL;
if (sunaddr->sun_family != AF_UNIX)
@@ -893,27 +919,7 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
}
spin_lock(&unix_table_lock);
-
- err = -EADDRINUSE;
- if (!sun_path[0]) {
- if (__unix_find_socket_byname(net, sunaddr, addr->len,
- sk->sk_type, hash)) {
- unix_release_addr(addr);
- goto out_unlock;
- }
-
- list = &unix_socket_table[addr->hash];
- } else {
- list = &unix_socket_table[path.dentry->d_inode->i_ino & (UNIX_HASH_SIZE-1)];
- u->path = path;
- }
-
- err = 0;
- __unix_remove_socket(sk);
- u->addr = addr;
- __unix_insert_socket(list, sk);
-
-out_unlock:
+ err = __unix_add_sock(&path, sk, addr, hash);
spin_unlock(&unix_table_lock);
out_up:
mutex_unlock(&u->readlock);
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| [RFC PATCH 1/5] net: cleanup unix_bind() a little [message #47537 is a reply to message #47535] |
Wed, 15 August 2012 16:22 |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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This will simplify further changes for unix_fbind().
---
net/unix/af_unix.c | 12 +++++-------
1 files changed, 5 insertions(+), 7 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 641f2e4..bc90ddb 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -880,10 +880,8 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
if (err)
goto out_mknod_dput;
err = security_path_mknod(&path, dentry, mode, 0);
- if (err)
- goto out_mknod_drop_write;
- err = vfs_mknod(path.dentry->d_inode, dentry, mode, 0);
-out_mknod_drop_write:
+ if (!err)
+ err = vfs_mknod(path.dentry->d_inode, dentry, mode, 0);
mnt_drop_write(path.mnt);
if (err)
goto out_mknod_dput;
@@ -896,9 +894,9 @@ out_mknod_drop_write:
spin_lock(&unix_table_lock);
+ err = -EADDRINUSE;
if (!sun_path[0]) {
- err = -EADDRINUSE;
- if (__unix_find_socket_byname(net, sunaddr, addr_len,
+ if (__unix_find_socket_byname(net, sunaddr, addr->len,
sk->sk_type, hash)) {
unix_release_addr(addr);
goto out_unlock;
@@ -906,7 +904,7 @@ out_mknod_drop_write:
list = &unix_socket_table[addr->hash];
} else {
- list = &unix_socket_table[dentry->d_inode->i_ino & (UNIX_HASH_SIZE-1)];
+ list = &unix_socket_table[path.dentry->d_inode->i_ino & (UNIX_HASH_SIZE-1)];
u->path = path;
}
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| [RFC PATCH 3/5] net: new protocol operation fbind() introduced [message #47538 is a reply to message #47535] |
Wed, 15 August 2012 16:22 |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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This operation is used to bind socket to specified file.
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
include/linux/net.h | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/include/linux/net.h b/include/linux/net.h
index e9ac2df..843cb75 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -157,6 +157,7 @@ struct kiocb;
struct sockaddr;
struct msghdr;
struct module;
+struct path;
struct proto_ops {
int family;
@@ -165,6 +166,7 @@ struct proto_ops {
int (*bind) (struct socket *sock,
struct sockaddr *myaddr,
int sockaddr_len);
+ int (*fbind) (struct file *file, struct socket *sock);
int (*connect) (struct socket *sock,
struct sockaddr *vaddr,
int sockaddr_len, int flags);
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| [RFC PATCH 4/5] net: fbind() for unix sockets protocol operations introduced [message #47539 is a reply to message #47535] |
Wed, 15 August 2012 16:22 |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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Path for unix_address is taken from passed file.
File inode have to be socket.
Since no sunaddr is present, addr->name is constructed at the place. It
obviously means, then path name can be truncated is it's longer then
UNIX_MAX_PATH.
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
net/unix/af_unix.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 76 insertions(+), 2 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index b26200d..2f34c9d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -286,12 +286,11 @@ static inline struct sock *unix_find_socket_byname(struct net *net,
return s;
}
-static struct sock *unix_find_socket_byinode(struct inode *i)
+static struct sock *__unix_find_socket_byinode(struct inode *i)
{
struct sock *s;
struct hlist_node *node;
- spin_lock(&unix_table_lock);
sk_for_each(s, node,
&unix_socket_table[i->i_ino & (UNIX_HASH_SIZE - 1)]) {
struct dentry *dentry = unix_sk(s)->path.dentry;
@@ -303,6 +302,15 @@ static struct sock *unix_find_socket_byinode(struct inode *i)
}
s = NULL;
found:
+ return s;
+}
+
+static struct sock *unix_find_socket_byinode(struct inode *i)
+{
+ struct sock *s;
+
+ spin_lock(&unix_table_lock);
+ s = __unix_find_socket_byinode(i);
spin_unlock(&unix_table_lock);
return s;
}
@@ -502,6 +510,7 @@ out:
static int unix_release(struct socket *);
static int unix_bind(struct socket *, struct sockaddr *, int);
+static int unix_fbind(struct file *file, struct socket *sock);
static int unix_stream_connect(struct socket *, struct sockaddr *,
int addr_len, int flags);
static int unix_socketpair(struct socket *, struct socket *);
@@ -542,6 +551,7 @@ static const struct proto_ops unix_stream_ops = {
.owner = THIS_MODULE,
.release = unix_release,
.bind = unix_bind,
+ .fbind = unix_fbind,
.connect = unix_stream_connect,
.socketpair = unix_socketpair,
.accept = unix_accept,
@@ -564,6 +574,7 @@ static const struct proto_ops unix_dgram_ops = {
.owner = THIS_MODULE,
.release = unix_release,
.bind = unix_bind,
+ .fbind = unix_fbind,
.connect = unix_dgram_connect,
.socketpair = unix_socketpair,
.accept = sock_no_accept,
@@ -586,6 +597,7 @@ static const struct proto_ops unix_seqpacket_ops = {
.owner = THIS_MODULE,
.release = unix_release,
.bind = unix_bind,
+ .fbind = unix_fbind,
.connect = unix_stream_connect,
.socketpair = unix_socketpair,
.accept = unix_accept,
@@ -843,6 +855,68 @@ static int __unix_add_sock(struct path *path, struct sock *sk,
}
+static int unix_fbind(struct file *f, struct socket *sock)
+{
+ struct sock *sk = sock->sk, *tmp;
+ struct unix_sock *u = unix_sk(sk);
+ struct unix_address *addr;
+ struct path *path = &f->f_path;
+ struct inode *inode = path->dentry->d_inode;
+ char *buf, *name;
+ int err;
+
+ err = -ENOTSOCK;
+ if (!S_ISSOCK(inode->i_mode))
+ goto out;
+
+ mutex_lock(&u->readlock);
+
+ err = -EINVAL;
+ if (u->addr)
+ goto out_up;
+
+ err = -ENOMEM;
+ buf = (char*)__get_free_page(GFP_KERNEL);
+ if (!buf)
+ goto out_up;
+
+ err = -EFAULT;
+ name = d_path(path, buf, PAGE_SIZE);
+ if (IS_ERR(name))
+ goto out_up_page;
+
+ addr = kmalloc(sizeof(*addr) + sizeof(struct sockaddr_un), GFP_KERNEL);
+ if (!addr)
+ goto out_up_page;
+
+ addr->name->sun_family = AF_UNIX;
+ addr->len = min(strlen(name), (size_t)UNIX_PATH_MAX);
+ memcpy(addr->name->sun_path, name, addr->len);
+ atomic_set(&addr->refcnt, 1);
+
+ spin_lock(&unix_table_lock);
+
+ err = -EADDRINUSE;
+ tmp = __unix_find_socket_byinode(inode);
+ if (tmp) {
+ sock_put(tmp);
+ unix_release_addr(addr);
+ goto out_unlock;
+ }
+
+ err = __unix_add_sock(path, sk, addr, 0);
+ path_get(path);
+
+out_unlock:
+ spin_unlock(&unix_table_lock);
+out_up_page:
+ free_page((unsigned long)buf);
+out_up:
+ mutex_unlock(&u->readlock);
+out:
+ return err;
+}
+
static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
struct sock *sk = sock->sk;
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| [RFC PATCH 5/5] syscall: sys_fbind() introduced [message #47540 is a reply to message #47535] |
Wed, 15 August 2012 16:22 |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
|
Senior Member |
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This syscall allows to bind socket to specified file descriptor.
Descriptor can be gained by simple open with O_PATH flag.
Socket node can be created by sys_mknod().
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
arch/x86/syscalls/syscall_32.tbl | 1 +
arch/x86/syscalls/syscall_64.tbl | 1 +
include/linux/syscalls.h | 1 +
kernel/sys_ni.c | 3 +++
net/socket.c | 25 +++++++++++++++++++++++++
5 files changed, 31 insertions(+), 0 deletions(-)
diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
index 7a35a6e..9594b82 100644
--- a/arch/x86/syscalls/syscall_32.tbl
+++ b/arch/x86/syscalls/syscall_32.tbl
@@ -356,3 +356,4 @@
347 i386 process_vm_readv sys_process_vm_readv compat_sys_process_vm_readv
348 i386 process_vm_writev sys_process_vm_writev compat_sys_process_vm_writev
349 i386 kcmp sys_kcmp
+350 i386 fbind sys_fbind
diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index 51171ae..f964df8 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -319,6 +319,7 @@
310 64 process_vm_readv sys_process_vm_readv
311 64 process_vm_writev sys_process_vm_writev
312 64 kcmp sys_kcmp
+313 common fbind sys_fbind
#
# x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 19439c7..9e78fa4 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -602,6 +602,7 @@ asmlinkage long sys_setsockopt(int fd, int level, int optname,
asmlinkage long sys_getsockopt(int fd, int level, int optname,
char __user *optval, int __user *optlen);
asmlinkage long sys_bind(int, struct sockaddr __user *, int);
+asmlinkage long sys_fbind(int, int);
asmlinkage long sys_connect(int, struct sockaddr __user *, int);
asmlinkage long sys_accept(int, struct sockaddr __user *, int __user *);
asmlinkage long sys_accept4(int, struct sockaddr __user *, int __user *, int);
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index dbff751..30c393a 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -206,3 +206,6 @@ cond_syscall(compat_sys_open_by_handle_at);
/* compare kernel pointers */
cond_syscall(sys_kcmp);
+
+cond_syscall(sys_fbind);
+
diff --git a/net/socket.c b/net/socket.c
index 6e0ccc0..67d9795 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1432,6 +1432,31 @@ out:
return err;
}
+SYSCALL_DEFINE2(fbind, int, fd, int, sk_fd)
+{
+ struct socket *sock;
+ int err, fput_sk, fput_fd;
+ struct file *file;
+
+ sock = sockfd_lookup_light(sk_fd, &err, &fput_sk);
+ if (!sock)
+ return err;
+
+ err = -EBADF;
+ file = fget_raw_light(fd, &fput_fd);
+ if (!file)
+ goto out_put_sk;
+
+ err = -EINVAL;
+ if (sock->ops->fbind)
+ err = sock->ops->fbind(file, sock);
+
+ fput_light(file, fput_fd);
+out_put_sk:
+ fput_light(sock->file, fput_sk);
+ return err;
+}
+
/*
* Bind a name to a socket. Nothing much to do here since it's
* the protocol's responsibility to handle the local address.
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| Re: [RFC PATCH 5/5] syscall: sys_fbind() introduced [message #47543 is a reply to message #47541] |
Wed, 15 August 2012 16:43 |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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15.08.2012 20:30, H. Peter Anvin пишет:
> On 08/15/2012 09:22 AM, Stanislav Kinsbursky wrote:
>> This syscall allows to bind socket to specified file descriptor.
>> Descriptor can be gained by simple open with O_PATH flag.
>> Socket node can be created by sys_mknod().
>>
>> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
>> ---
>> arch/x86/syscalls/syscall_32.tbl | 1 +
>> arch/x86/syscalls/syscall_64.tbl | 1 +
>> include/linux/syscalls.h | 1 +
>> kernel/sys_ni.c | 3 +++
>> net/socket.c | 25 +++++++++++++++++++++++++
>> 5 files changed, 31 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
>> index 7a35a6e..9594b82 100644
>> --- a/arch/x86/syscalls/syscall_32.tbl
>> +++ b/arch/x86/syscalls/syscall_32.tbl
>> @@ -356,3 +356,4 @@
>> 347 i386 process_vm_readv sys_process_vm_readv compat_sys_process_vm_readv
>> 348 i386 process_vm_writev sys_process_vm_writev compat_sys_process_vm_writev
>> 349 i386 kcmp sys_kcmp
>> +350 i386 fbind sys_fbind
>
> i386 uses socketcalls... perhaps it shouldn't (socketcalls are pretty
> much an abomination), but for socketcall-based architectures this really
> should be a socketcall.
>
Thanks, Peter. I'll rework this.
> Don't you also need fconnect()? Or is that simply handled by allowing
> open() without O_PATH?
>
Yes, I need it.
If this approach will be accepted, then I'll send one more patch set for fconnect.
> -hpa
>
--
Best regards,
Stanislav Kinsbursky
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| Re: [RFC PATCH 0/5] net: socket bind to file descriptor introduced [message #47743 is a reply to message #47607] |
Tue, 04 September 2012 19:00 |
bfields
Messages: 107
Registered: September 2007
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Senior Member |
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On Mon, Aug 20, 2012 at 02:18:13PM +0400, Stanislav Kinsbursky wrote:
> 16.08.2012 07:03, Eric W. Biederman пишет:
> >Stanislav Kinsbursky <skinsbursky@parallels.com> writes:
> >
> >>This patch set introduces new socket operation and new system call:
> >>sys_fbind(), which allows to bind socket to opened file.
> >>File to bind to can be created by sys_mknod(S_IFSOCK) and opened by
> >>open(O_PATH).
> >>
> >>This system call is especially required for UNIX sockets, which has name
> >>lenght limitation.
> >>
> >>The following series implements...
> >
> >Hmm. I just realized this patchset is even sillier than I thought.
> >
> >Stanislav is the problem you are ultimately trying to solve nfs clients
> >in a container connecting to the wrong user space rpciod?
> >
>
> Hi, Eric.
> The problem you mentioned was the reason why I started to think about this.
> But currently I believe, that limitations in unix sockets connect or
> bind should be removed, because it will be useful it least for CRIU
> project.
>
> >Aka net/sunrpc/xprtsock.c:xs_setup_local only taking an absolute path
> >and then creating a delayed work item to actually open the unix domain
> >socket?
> >
> >The straight correct and straight forward thing to do appears to be:
> >- Capture the root from current->fs in xs_setup_local.
> >- In xs_local_finish_connect change current->fs.root to the captured
> > version of root before kernel_connect, and restore current->fs.root
> > after kernel_connect.
> >
> >It might not be a bad idea to implement open on unix domain sockets in
> >a filesystem as create(AF_LOCAL)+connect() which would allow you to
> >replace __sock_create + kernel_connect with a simple file_open_root.
> >
>
> I like the idea of introducing new family (AF_LOCAL_AT for example)
> and new sockaddr for connecting or binding from specified root. The
> only thing I'm worrying is passing file descriptor to unix bind or
> connect routine. Because this approach doesn't provide easy way to
> use such family and sockaddr in kernel (like in NFS example).
>
> >But I think the simple scheme of:
> >struct path old_root;
> >old_root = current->fs.root;
> >kernel_connect(...);
> >current->fs.root = old_root;
> >
> >Is more than sufficient and will remove the need for anything
> >except a purely local change to get nfs clients to connect from
> >containers.
> >
>
> That was my first idea.
So is this what you're planning on doing now?
> And probably it would be worth to change all
> fs_struct to support sockets with relative path.
> What do you think about it?
I didn't understand the question. Are you suggesting that changes to
fs_struct would be required to make this work? I don't see why.
--b.
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| Re: [RFC PATCH 0/5] net: socket bind to file descriptor introduced [message #48215 is a reply to message #47743] |
Fri, 05 October 2012 20:00 |
bfields
Messages: 107
Registered: September 2007
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Senior Member |
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On Tue, Sep 04, 2012 at 03:00:07PM -0400, bfields wrote:
> On Mon, Aug 20, 2012 at 02:18:13PM +0400, Stanislav Kinsbursky wrote:
> > 16.08.2012 07:03, Eric W. Biederman пишет:
> > >Stanislav Kinsbursky <skinsbursky@parallels.com> writes:
> > >
> > >>This patch set introduces new socket operation and new system call:
> > >>sys_fbind(), which allows to bind socket to opened file.
> > >>File to bind to can be created by sys_mknod(S_IFSOCK) and opened by
> > >>open(O_PATH).
> > >>
> > >>This system call is especially required for UNIX sockets, which has name
> > >>lenght limitation.
> > >>
> > >>The following series implements...
> > >
> > >Hmm. I just realized this patchset is even sillier than I thought.
> > >
> > >Stanislav is the problem you are ultimately trying to solve nfs clients
> > >in a container connecting to the wrong user space rpciod?
> > >
> >
> > Hi, Eric.
> > The problem you mentioned was the reason why I started to think about this.
> > But currently I believe, that limitations in unix sockets connect or
> > bind should be removed, because it will be useful it least for CRIU
> > project.
> >
> > >Aka net/sunrpc/xprtsock.c:xs_setup_local only taking an absolute path
> > >and then creating a delayed work item to actually open the unix domain
> > >socket?
> > >
> > >The straight correct and straight forward thing to do appears to be:
> > >- Capture the root from current->fs in xs_setup_local.
> > >- In xs_local_finish_connect change current->fs.root to the captured
> > > version of root before kernel_connect, and restore current->fs.root
> > > after kernel_connect.
> > >
> > >It might not be a bad idea to implement open on unix domain sockets in
> > >a filesystem as create(AF_LOCAL)+connect() which would allow you to
> > >replace __sock_create + kernel_connect with a simple file_open_root.
> > >
> >
> > I like the idea of introducing new family (AF_LOCAL_AT for example)
> > and new sockaddr for connecting or binding from specified root. The
> > only thing I'm worrying is passing file descriptor to unix bind or
> > connect routine. Because this approach doesn't provide easy way to
> > use such family and sockaddr in kernel (like in NFS example).
> >
> > >But I think the simple scheme of:
> > >struct path old_root;
> > >old_root = current->fs.root;
> > >kernel_connect(...);
> > >current->fs.root = old_root;
> > >
> > >Is more than sufficient and will remove the need for anything
> > >except a purely local change to get nfs clients to connect from
> > >containers.
> > >
> >
> > That was my first idea.
>
> So is this what you're planning on doing now?
What ever happened to this?
--b.
>
> > And probably it would be worth to change all
> > fs_struct to support sockets with relative path.
> > What do you think about it?
>
> I didn't understand the question. Are you suggesting that changes to
> fs_struct would be required to make this work? I don't see why.
>
> --b.
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| Re: [RFC PATCH 0/5] net: socket bind to file descriptor introduced [message #48223 is a reply to message #48215] |
Mon, 08 October 2012 08:37 |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
|
Senior Member |
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06.10.2012 00:00, J. Bruce Fields пишет:
> On Tue, Sep 04, 2012 at 03:00:07PM -0400, bfields wrote:
>> On Mon, Aug 20, 2012 at 02:18:13PM +0400, Stanislav Kinsbursky wrote:
>>> 16.08.2012 07:03, Eric W. Biederman пишет:
>>>> Stanislav Kinsbursky <skinsbursky@parallels.com> writes:
>>>>
>>>>> This patch set introduces new socket operation and new system call:
>>>>> sys_fbind(), which allows to bind socket to opened file.
>>>>> File to bind to can be created by sys_mknod(S_IFSOCK) and opened by
>>>>> open(O_PATH).
>>>>>
>>>>> This system call is especially required for UNIX sockets, which has name
>>>>> lenght limitation.
>>>>>
>>>>> The following series implements...
>>>>
>>>> Hmm. I just realized this patchset is even sillier than I thought.
>>>>
>>>> Stanislav is the problem you are ultimately trying to solve nfs clients
>>>> in a container connecting to the wrong user space rpciod?
>>>>
>>>
>>> Hi, Eric.
>>> The problem you mentioned was the reason why I started to think about this.
>>> But currently I believe, that limitations in unix sockets connect or
>>> bind should be removed, because it will be useful it least for CRIU
>>> project.
>>>
>>>> Aka net/sunrpc/xprtsock.c:xs_setup_local only taking an absolute path
>>>> and then creating a delayed work item to actually open the unix domain
>>>> socket?
>>>>
>>>> The straight correct and straight forward thing to do appears to be:
>>>> - Capture the root from current->fs in xs_setup_local.
>>>> - In xs_local_finish_connect change current->fs.root to the captured
>>>> version of root before kernel_connect, and restore current->fs.root
>>>> after kernel_connect.
>>>>
>>>> It might not be a bad idea to implement open on unix domain sockets in
>>>> a filesystem as create(AF_LOCAL)+connect() which would allow you to
>>>> replace __sock_create + kernel_connect with a simple file_open_root.
>>>>
>>>
>>> I like the idea of introducing new family (AF_LOCAL_AT for example)
>>> and new sockaddr for connecting or binding from specified root. The
>>> only thing I'm worrying is passing file descriptor to unix bind or
>>> connect routine. Because this approach doesn't provide easy way to
>>> use such family and sockaddr in kernel (like in NFS example).
>>>
>>>> But I think the simple scheme of:
>>>> struct path old_root;
>>>> old_root = current->fs.root;
>>>> kernel_connect(...);
>>>> current->fs.root = old_root;
>>>>
>>>> Is more than sufficient and will remove the need for anything
>>>> except a purely local change to get nfs clients to connect from
>>>> containers.
>>>>
>>>
>>> That was my first idea.
>>
>> So is this what you're planning on doing now?
>
> What ever happened to this?
>
Sorry, was busy.
I'll prepare patch today, I hope.
> --b.
>
>>
>>> And probably it would be worth to change all
>>> fs_struct to support sockets with relative path.
>>> What do you think about it?
>>
>> I didn't understand the question. Are you suggesting that changes to
>> fs_struct would be required to make this work? I don't see why.
>>
>> --b.
--
Best regards,
Stanislav Kinsbursky
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