cifs: Allow binding to local IP address.

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, ...

Acked-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Dr. David Holder <david.holder@erion.co.uk>
Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

3 files changed, 108 insertions, 2 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index b7431afdd76d..1b6ddd6f760f 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -36,6 +36,7 @@
 #include <linux/kthread.h>
 #include <linux/freezer.h>
 #include <linux/smp_lock.h>
+#include <net/ipv6.h>
 #include "cifsfs.h"
 #include "cifspdu.h"
 #define DECLARE_GLOBALS_HERE
@@ -367,6 +368,8 @@ 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 +377,22 @@ cifs_show_options(struct seq_file *s, struct vfsmount *m)
         if (tcon->ses->domainName)
                 seq_printf(s, ",domain=%s", tcon->ses->domainName);
 
+        if (srcaddr->sa_family != AF_UNSPEC) {
+                struct sockaddr_in *saddr4;
+                struct sockaddr_in6 *saddr6;
+                saddr4 = (struct sockaddr_in *)srcaddr;
+                saddr6 = (struct sockaddr_in6 *)srcaddr;
+                if (srcaddr->sa_family == AF_INET6)
+                        seq_printf(s, ",srcaddr=%pI6c",
+                                   &saddr6->sin6_addr);
+                else if (srcaddr->sa_family == AF_INET)
+                        seq_printf(s, ",srcaddr=%pI4",
+                                   &saddr4->sin_addr.s_addr);
+                else
+                        seq_printf(s, ",srcaddr=BAD-AF:%i",
+                                   (int)(srcaddr->sa_family));
+        }
+
         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/cifsglob.h b/fs/cifs/cifsglob.h
index c68f31cf4550..6ef0efaf68d4 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -139,6 +139,7 @@ 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 c99760a523bf..fa884520fb84 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -105,6 +105,7 @@ 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;
 };
 
@@ -1046,6 +1047,22 @@ cifs_parse_mount_options(char *options, const char *devname,
                                                     "long\n");
                                 return 1;
                         }
+                } else if (strnicmp(data, "srcaddr", 7) == 0) {
+                        vol->srcaddr.ss_family = AF_UNSPEC;
+
+                        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
@@ -1374,8 +1391,36 @@ cifs_parse_mount_options(char *options, const char *devname,
         return 0;
 }
 
+/** Returns true if srcaddr isn't specified and rhs isn't
+ * specified, or if srcaddr is specified and
+ * matches the IP address of the rhs argument.
+ */
+static bool
+srcip_matches(struct sockaddr *srcaddr, struct sockaddr *rhs)
+{
+        switch (srcaddr->sa_family) {
+        case AF_UNSPEC:
+                return (rhs->sa_family == AF_UNSPEC);
+        case AF_INET: {
+                struct sockaddr_in *saddr4 = (struct sockaddr_in *)srcaddr;
+                struct sockaddr_in *vaddr4 = (struct sockaddr_in *)rhs;
+                return (saddr4->sin_addr.s_addr == vaddr4->sin_addr.s_addr);
+        }
+        case AF_INET6: {
+                struct sockaddr_in6 *saddr6 = (struct sockaddr_in6 *)srcaddr;
+                struct sockaddr_in6 *vaddr6 = (struct sockaddr_in6 *)&rhs;
+                return ipv6_addr_equal(&saddr6->sin6_addr, &vaddr6->sin6_addr);
+        }
+        default:
+                WARN_ON(1);
+                return false; /* don't expect to be here */
+        }
+}
+
+
 static bool
-match_address(struct TCP_Server_Info *server, struct sockaddr *addr)
+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;
@@ -1402,6 +1447,9 @@ match_address(struct TCP_Server_Info *server, struct sockaddr *addr)
                 break;
         }
 
+        if (!srcip_matches(srcaddr, (struct sockaddr *)&server->srcaddr))
+                return false;
+
         return true;
 }
 
@@ -1469,7 +1517,8 @@ 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))
@@ -1584,6 +1633,8 @@ 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) {
@@ -1999,6 +2050,33 @@ static void rfc1002mangle(char *target, char *source, unsigned int length)
 
 }
 
+static int
+bind_socket(struct TCP_Server_Info *server)
+{
+        int rc = 0;
+        if (server->srcaddr.ss_family != AF_UNSPEC) {
+                /* Bind to the specified local IP address */
+                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)
+                                cERROR(1, "cifs: "
+                                       "Failed to bind to: %pI6c, error: %d\n",
+                                       &saddr6->sin6_addr, rc);
+                        else
+                                cERROR(1, "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)
@@ -2024,6 +2102,10 @@ ipv4_connect(struct TCP_Server_Info *server)
                 cifs_reclassify_socket4(socket);
         }
 
+        rc = bind_socket(server);
+        if (rc < 0)
+                return rc;
+
         /* user overrode default port */
         if (server->addr.sockAddr.sin_port) {
                 rc = socket->ops->connect(socket, (struct sockaddr *)
@@ -2186,6 +2268,10 @@ ipv6_connect(struct TCP_Server_Info *server)
                 cifs_reclassify_socket6(socket);
         }
 
+        rc = bind_socket(server);
+        if (rc < 0)
+                return rc;
+
         /* user overrode default port */
         if (server->addr.sockAddr6.sin6_port) {
                 rc = socket->ops->connect(socket,