Re: [cifs] cifs: Allow binding to local IP address.

[Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>]

On Mon, 30 Aug 2010 22:40:22 -0700
Ben Greear <greearb-my8/4N5VtI7c+919tysfdA@public.gmane.org> wrote:

> When using multi-homed machines, it's nice to be able to specify
> the local IP to use for outbound connections.  This patch gives
> cifs the ability to bind to a particular IP address.
> 
>   Usage:  mount -t cifs -o srcaddr=192.168.1.50,user=foo, ...
>   Usage:  mount -t cifs -o srcaddr=2002::100:1,user=foo, ...
> 
> Signed-off-by: Ben Greear <greearb-my8/4N5VtI7c+919tysfdA@public.gmane.org>
> ---
> :100644 100644 b7431af... 4510f4d... M	fs/cifs/cifsfs.c
> :100644 100644 d82f5fb... d6f0a7d... M	fs/cifs/cifsfs.h
> :100644 100644 c9d0cfc... 784fd4a... M	fs/cifs/cifsglob.h
> :100644 100644 ec0ea4a... 9a3175b... M	fs/cifs/connect.c
> :100644 100644 ab70a3f... 735989a... M	net/ipv6/addrconf.c
>  fs/cifs/cifsfs.c    |   32 ++++++++++++++++++
>  fs/cifs/cifsfs.h    |    3 ++
>  fs/cifs/cifsglob.h  |    1 +
>  fs/cifs/connect.c   |   91 +++++++++++++++++++++++++++++++++++++++++++++++++-
>  net/ipv6/addrconf.c |    1 +
>  5 files changed, 126 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index b7431af..4510f4d 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -357,6 +357,23 @@ cifs_show_address(struct seq_file *s, struct TCP_Server_Info *server)
>  	}
>  }
>  
> +bool
> +cifs_addr_is_specified(struct sockaddr *srcaddr) {
> +	struct sockaddr_in *saddr4 = (struct sockaddr_in *)srcaddr;
> +	struct sockaddr_in6 *saddr6 = (struct sockaddr_in6 *)srcaddr;
> +	switch (srcaddr->sa_family) {
> +	case AF_INET:
> +		return saddr4->sin_addr.s_addr != 0;
						^^^^
					nit: should probably be htonl(INADDR_ANY)
> +#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
> +	case AF_INET6:
> +		/* in6addr_any isn't available if IPv6 isn't compiled in */
> +		return (memcmp(&in6addr_any, &saddr6->sin6_addr,
> +			       sizeof(in6addr_any)) != 0);
> +#endif
> +	}
> +	return false;
> +}
> +
>  /*
>   * cifs_show_options() is for displaying mount options in /proc/mounts.
>   * Not all settable options are displayed but most of the important
> @@ -367,6 +384,8 @@ cifs_show_options(struct seq_file *s, struct vfsmount *m)
>  {
>  	struct cifs_sb_info *cifs_sb = CIFS_SB(m->mnt_sb);
>  	struct cifsTconInfo *tcon = cifs_sb->tcon;
> +	struct sockaddr *srcaddr;
> +	srcaddr = (struct sockaddr *)(&tcon->ses->server->srcaddr);
>  
>  	seq_printf(s, ",unc=%s", tcon->treeName);
>  	if (tcon->ses->userName)
> @@ -374,6 +393,19 @@ cifs_show_options(struct seq_file *s, struct vfsmount *m)
>  	if (tcon->ses->domainName)
>  		seq_printf(s, ",domain=%s", tcon->ses->domainName);
>  
> +	if (cifs_addr_is_specified(srcaddr)) {
> +		struct sockaddr_in *saddr4;
> +		struct sockaddr_in6 *saddr6;
> +		saddr4 = (struct sockaddr_in *)srcaddr;
> +		saddr6 = (struct sockaddr_in6 *)srcaddr;
> +		if (saddr6->sin6_family == AF_INET6)
> +			seq_printf(s, ",srcaddr=%pI6c",
> +				   &saddr6->sin6_addr);
> +		else
> +			seq_printf(s, ",srcaddr=%pI4",
> +				   &saddr4->sin_addr.s_addr);
> +	}
> +
>  	seq_printf(s, ",uid=%d", cifs_sb->mnt_uid);
>  	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_OVERR_UID)
>  		seq_printf(s, ",forceuid");
> diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
> index d82f5fb..d6f0a7d 100644
> --- a/fs/cifs/cifsfs.h
> +++ b/fs/cifs/cifsfs.h
> @@ -110,6 +110,9 @@ extern ssize_t	cifs_getxattr(struct dentry *, const char *, void *, size_t);
>  extern ssize_t	cifs_listxattr(struct dentry *, char *, size_t);
>  extern long cifs_ioctl(struct file *filep, unsigned int cmd, unsigned long arg);
>  
> +struct sockaddr;
> +extern bool cifs_addr_is_specified(struct sockaddr *srcaddr);
> +
>  #ifdef CONFIG_CIFS_EXPERIMENTAL
>  extern const struct export_operations cifs_export_ops;
>  #endif /* EXPERIMENTAL */
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index c9d0cfc..784fd4a 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -157,6 +157,7 @@ struct TCP_Server_Info {
>  		struct sockaddr_in sockAddr;
>  		struct sockaddr_in6 sockAddr6;
>  	} addr;
> +	struct sockaddr_storage srcaddr; /* locally bind to this IP */
>  	wait_queue_head_t response_q;
>  	wait_queue_head_t request_q; /* if more than maxmpx to srvr must block*/
>  	struct list_head pending_mid_q;
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index ec0ea4a..9a3175b 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -49,6 +49,7 @@
>  #include "rfc1002pdu.h"
>  #include "cn_cifs.h"
>  #include "fscache.h"
> +#include "cifsfs.h"
>  
>  #define CIFS_PORT 445
>  #define RFC1001_PORT 139
> @@ -105,6 +106,7 @@ struct smb_vol {
>  	bool sockopt_tcp_nodelay:1;
>  	unsigned short int port;
>  	char *prepath;
> +	struct sockaddr_storage srcaddr; /* allow binding to a local IP */
>  	struct nls_table *local_nls;
>  };
>  
> @@ -1064,6 +1066,22 @@ cifs_parse_mount_options(char *options, const char *devname,
>  						    "long\n");
>  				return 1;
>  			}
> +		} else if (strnicmp(data, "srcaddr", 8) == 0) {
> +			memset(&vol->srcaddr, 0, sizeof(vol->srcaddr));
			^^^^^^^^^
			Is this necessary? vol is kzalloc'ed so it
			should be zeroed out already. Or are you
			worried about people specifying srcaddr= more
			than once?

> +
> +			if (!value || !*value) {
> +				printk(KERN_WARNING "CIFS: srcaddr value"
> +				       " not specified.\n");
> +				return 1;	/* needs_arg; */
> +			}
> +			i = cifs_convert_address((struct sockaddr *)&vol->srcaddr,
> +						 value, strlen(value));
> +			if (i < 0) {
> +				printk(KERN_WARNING "CIFS:  Could not parse"
> +				       " srcaddr: %s\n",
> +				       value);
> +				return 1;
> +			}
>  		} else if (strnicmp(data, "prefixpath", 10) == 0) {
>  			if (!value || !*value) {
>  				printk(KERN_WARNING
> @@ -1392,8 +1410,37 @@ cifs_parse_mount_options(char *options, const char *devname,
>  	return 0;
>  }
>  
> +/** Returns true if srcaddr isn't specified or if it matches
> + * the IP address of the rhs argument.
> + */
>  static bool
> -match_address(struct TCP_Server_Info *server, struct sockaddr *addr)
> +srcip_matches(struct sockaddr *srcaddr, struct sockaddr *rhs)
> +{
> +	if (cifs_addr_is_specified(srcaddr)) {

	Just wondering what the expected behavior would be here...

	Suppose I have a clustered IP address set up, and I want to
	ensure that one of my CIFS mounts use that as the srcaddr. Now,
	suppose I make another mount to the same server, but don't
	specify the srcaddr there. That mount uses the same socket as
	the first one (that is bound to the srcaddr). Now, suppose I
	unmount the first mount and then fail over the IP address. What
	happens to the second one? (Nothing good, I'd wager...)

	Perhaps we should consider using a different socket when the
	srcaddr isn't specified?

> +		struct sockaddr_in *saddr4 = (struct sockaddr_in *)srcaddr;
> +		struct sockaddr_in6 *saddr6 = (struct sockaddr_in6 *)srcaddr;
> +		struct sockaddr_in *vaddr4 = (struct sockaddr_in *)rhs;
> +		struct sockaddr_in6 *vaddr6 = (struct sockaddr_in6 *)&rhs;
> +
> +		switch (srcaddr->sa_family) {
> +		case AF_INET:
> +			if (saddr4->sin_addr.s_addr != vaddr4->sin_addr.s_addr)
> +				return false;
> +			break;
> +		case AF_INET6:
> +			if (memcmp(&saddr6->sin6_addr, &vaddr6->sin6_addr,
> +				   sizeof(saddr6->sin6_addr)) != 0)

			^^^ should use ipv6_addr_equal, unless there's some reason not to do so...

> +				return false;
> +			break;
> +		}
> +	}
> +	return true;
> +}
> +
> +
> +static bool
> +match_address(struct TCP_Server_Info *server, struct sockaddr *addr,
> +	      struct sockaddr *srcaddr)
>  {
>  	struct sockaddr_in *addr4 = (struct sockaddr_in *)addr;
>  	struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *)addr;
> @@ -1420,6 +1467,9 @@ match_address(struct TCP_Server_Info *server, struct sockaddr *addr)
>  		break;
>  	}
>  
> +	if (!srcip_matches(srcaddr, (struct sockaddr *)&server->srcaddr))
> +		return false;
> +
>  	return true;
>  }
>  
> @@ -1487,7 +1537,8 @@ cifs_find_tcp_session(struct sockaddr *addr, struct smb_vol *vol)
>  		if (server->tcpStatus == CifsNew)
>  			continue;
>  
> -		if (!match_address(server, addr))
> +		if (!match_address(server, addr,
> +				   (struct sockaddr *)&vol->srcaddr))
>  			continue;
>  
>  		if (!match_security(server, vol))
> @@ -1602,6 +1653,8 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
>  	 * no need to spinlock this init of tcpStatus or srv_count
>  	 */
>  	tcp_ses->tcpStatus = CifsNew;
> +	memcpy(&tcp_ses->srcaddr, &volume_info->srcaddr,
> +	       sizeof(tcp_ses->srcaddr));
>  	++tcp_ses->srv_count;
>  
>  	if (addr.ss_family == AF_INET6) {
> @@ -1678,6 +1731,9 @@ cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb_vol *vol)
>  				    vol->password ? vol->password : "",
>  				    MAX_PASSWORD_SIZE))
>  				continue;
> +			if (!srcip_matches((struct sockaddr *)&server->srcaddr,
> +					   (struct sockaddr *)&ses->server->srcaddr))
> +				continue;

			^^^ there should be no need for this. By the
			time you get here, you've already determined
			whether you can use the same socket as another
			one (via the check in match_address).

>  		}
>  		++ses->ses_count;
>  		write_unlock(&cifs_tcp_ses_lock);
> @@ -2026,6 +2082,33 @@ static void rfc1002mangle(char *target, char *source, unsigned int length)
>  
>  }
>  
> +static int
> +bind_socket(struct TCP_Server_Info *server)
> +{
> +	int rc = 0;
> +	if (cifs_addr_is_specified((struct sockaddr *)&server->srcaddr)) {
> +		/* Bind to the local IP address if specified */
> +		struct socket *socket = server->ssocket;
> +		rc = socket->ops->bind(socket,
> +				       (struct sockaddr *) &server->srcaddr,
> +				       sizeof(server->srcaddr));
> +		if (rc < 0) {
> +			struct sockaddr_in *saddr4;
> +			struct sockaddr_in6 *saddr6;
> +			saddr4 = (struct sockaddr_in *)&server->srcaddr;
> +			saddr6 = (struct sockaddr_in6 *)&server->srcaddr;
> +			if (saddr6->sin6_family == AF_INET6)
> +				printk(KERN_WARNING "cifs: "
> +				       "Failed to bind to: %pI6c, error: %d\n",
> +				       &saddr6->sin6_addr, rc);
> +			else
> +				printk(KERN_WARNING "cifs: "
> +				       "Failed to bind to: %pI4, error: %d\n",
> +				       &saddr4->sin_addr.s_addr, rc);
> +		}
> +	}
> +	return rc;
> +}
>  
>  static int
>  ipv4_connect(struct TCP_Server_Info *server)
> @@ -2051,6 +2134,8 @@ ipv4_connect(struct TCP_Server_Info *server)
>  		cifs_reclassify_socket4(socket);
>  	}
>  
> +	bind_socket(server);
> +
>  	/* user overrode default port */
>  	if (server->addr.sockAddr.sin_port) {
>  		rc = socket->ops->connect(socket, (struct sockaddr *)
> @@ -2213,6 +2298,8 @@ ipv6_connect(struct TCP_Server_Info *server)
>  		cifs_reclassify_socket6(socket);
>  	}
>  
> +	bind_socket(server);
> +
>  	/* user overrode default port */
>  	if (server->addr.sockAddr6.sin6_port) {
>  		rc = socket->ops->connect(socket,
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index ab70a3f..735989a 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -230,6 +230,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
>  
>  /* IPv6 Wildcard Address and Loopback Address defined by RFC2553 */
>  const struct in6_addr in6addr_any = IN6ADDR_ANY_INIT;
> +EXPORT_SYMBOL(in6addr_any);

There should be no need at all to touch stuff outside of cifs.ko, at
least, not in this patch. If you want to do this, you need to do it as
a separate patch and float it in linux-netdev or someplace like that.

In the meantime, I'd suggest declaring a private in6_addr variable and
initializing it to IN6ADDR_ANY_INIT (similar to what the sunrpc code
does).

>  const struct in6_addr in6addr_loopback = IN6ADDR_LOOPBACK_INIT;
>  const struct in6_addr in6addr_linklocal_allnodes = IN6ADDR_LINKLOCAL_ALLNODES_INIT;
>  const struct in6_addr in6addr_linklocal_allrouters = IN6ADDR_LINKLOCAL_ALLROUTERS_INIT;


-- 
Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>