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

[J. Bruce Fields]

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

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?)

--b.

> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky at parallels.com>
> ---
>  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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