Re: [RFC PATCH 1/2] unix sockets: add ability for search for peer from passed root

10.08.2012 22:10, J. Bruce Fields пишет:

On Fri, Aug 10, 2012 at 04:57:30PM +0400, Stanislav Kinsbursky wrote:

quoted

This helper is used stream sockets yet.
All is simple: if non-NULL struct path was passed to unix_find_other(), then
vfs_path_lookup() is called instead of kern_path().

I'm having some trouble parsing the changelog.  Maybe something like?:

	unix sockets: add ability to look up using passed-in root

	Export a unix_stream_connect_root() helper that allows a caller
	to optionally pass in a root path, in which case the lookup will
	be done relative to the given path instead of the current
	working directory.

Yep, your variant is much better. Thanks.

I guess this is a question for the networking people, but: will it cause
problems to have sunrpc calling directly into the unix socket code?

(And if so, what would be the alternative: define some variant of
sockaddr_un that includes the root path?  Something better?)

That was my first idea. But there are problems with this solution (add 
root path to sockaddr_un) :
1) sockaddr_un size will change. I don't know, how this will affect 
user-space. Of course, we can introduce something like:

struct sockaddr_un_kern {
struct sockaddr_un un;
struct path *path;
}

But even in this case we need to color this structure somehow (for 
example, set path to NULL for simple connect or bind call) . And to add 
this color, we have to separate sys_connect () from our 
sock->ops->connect() call. And I don't really know how to do it since we 
don't have any info about socket type in sys_connect () in hands. I.e. 
we have it, but then we have to add some specific UNIX socket logic to 
completely generic sys_connect () and sys_bind () .

--b.

quoted

Signed-off-by: Stanislav Kinsbursky <redacted>
---
  include/net/af_unix.h |    2 ++
  net/unix/af_unix.c    |   25 ++++++++++++++++++-------
  2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 2ee33da..559467e 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h

@@ -67,6 +67,8 @@ struct unix_sock {
  
  long unix_inq_len(struct sock *sk);
  long unix_outq_len(struct sock *sk);
+int unix_stream_connect_root(struct path *root, struct socket *sock,
+			     struct sockaddr *uaddr, int addr_len, int flags);
  
  #ifdef CONFIG_SYSCTL
  extern int unix_sysctl_register(struct net *net);

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 641f2e4..a790ebc 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c

@@ -759,7 +759,7 @@ out:	mutex_unlock(&u->readlock);
  	return err;
  }
  
-static struct sock *unix_find_other(struct net *net,
+static struct sock *unix_find_other(struct net *net, struct path *root,
  				    struct sockaddr_un *sunname, int len,
  				    int type, unsigned int hash, int *error)
  {

@@ -769,7 +769,11 @@ static struct sock *unix_find_other(struct net *net,
  
  	if (sunname->sun_path[0]) {
  		struct inode *inode;
-		err = kern_path(sunname->sun_path, LOOKUP_FOLLOW, &path);
+
+		if (root)
+			err = vfs_path_lookup(root->dentry, root->mnt, sunname->sun_path, LOOKUP_FOLLOW, &path);
+		else
+			err = kern_path(sunname->sun_path, LOOKUP_FOLLOW, &path);
  		if (err)
  			goto fail;
  		inode = path.dentry->d_inode;

@@ -979,7 +983,7 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
  			goto out;
  
  restart:
-		other = unix_find_other(net, sunaddr, alen, sock->type, hash, &err);
+		other = unix_find_other(net, NULL, sunaddr, alen, sock->type, hash, &err);
  		if (!other)
  			goto out;
  

@@ -1053,8 +1057,8 @@ static long unix_wait_for_peer(struct sock *other, long timeo)
  	return timeo;
  }
  
-static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
-			       int addr_len, int flags)
+int unix_stream_connect_root(struct path *root, struct socket *sock,
+			     struct sockaddr *uaddr, int addr_len, int flags)
  {
  	struct sockaddr_un *sunaddr = (struct sockaddr_un *)uaddr;
  	struct sock *sk = sock->sk;

@@ -1098,7 +1102,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
  
  restart:
  	/*  Find listening sock. */
-	other = unix_find_other(net, sunaddr, addr_len, sk->sk_type, hash, &err);
+	other = unix_find_other(net, root, sunaddr, addr_len, sk->sk_type, hash, &err);
  	if (!other)
  		goto out;
  

@@ -1227,6 +1231,13 @@ out:
  		sock_put(other);
  	return err;
  }
+EXPORT_SYMBOL_GPL(unix_stream_connect_root);
+
+static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
+				    int addr_len, int flags)
+{
+	return unix_stream_connect_root(NULL, sock, uaddr, addr_len, flags);
+}
  
  static int unix_socketpair(struct socket *socka, struct socket *sockb)
  {

@@ -1508,7 +1519,7 @@ restart:
  		if (sunaddr == NULL)
  			goto out_free;
  
-		other = unix_find_other(net, sunaddr, namelen, sk->sk_type,
+		other = unix_find_other(net, NULL, sunaddr, namelen, sk->sk_type,
  					hash, &err);
  		if (other == NULL)
  			goto out_free;

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