cifs: handle hostnames that resolve to same ip in failover

In order to support reconnect to hostnames that resolve to same ip
address, besides relying on the currently set hostname to match DFS
targets, attempt to resolve the targets and then match their addresses
with the reconnected server ip address.

For instance, if we have two hostnames "FOO" and "BAR", and both
resolve to the same ip address, we would be able to handle failover in
DFS paths like

    \\FOO\dfs\link1 -> [ \BAZ\share2 (*), \BAR\share1 ]
    \\FOO\dfs\link2 -> [ \BAZ\share2 (*), \FOO\share1 ]

so when "BAZ" is no longer accessible, link1 and link2 would get
reconnected despite having different target hostnames.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 12a895e02db405285469d6b4a2f2f1c842f996fa..311d8e86c5a84db1ddcc95e0432b3511426ad2b0 100644 (file)
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -89,6 +89,7 @@ extern void cifs_mid_q_entry_release(struct mid_q_entry *midEntry);
 extern void cifs_wake_up_task(struct mid_q_entry *mid);
 extern int cifs_handle_standard(struct TCP_Server_Info *server,
                                struct mid_q_entry *mid);
+extern bool cifs_match_ipaddr(struct sockaddr *srcaddr, struct sockaddr *rhs);
 extern int cifs_discard_remaining_data(struct TCP_Server_Info *server);
 extern int cifs_call_async(struct TCP_Server_Info *server,
                        struct smb_rqst *rqst,
@@ -616,6 +617,10 @@ static inline int get_dfs_path(const unsigned int xid, struct cifs_ses *ses,
        return dfs_cache_find(xid, ses, nls_codepage, remap, old_path,
                              referral, NULL);
 }
+
+int match_target_ip(struct TCP_Server_Info *server,
+                   const char *share, size_t share_len,
+                   bool *result);
 #endif
 
 static inline int cifs_create_options(struct cifs_sb_info *cifs_sb, int options)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index d62f9175c546f0456628b8560d52ae192ec45ae2..5a684f9ac883481f2d87a70cfe54644bdf848a7b 100644 (file)
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -129,6 +129,7 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
                                 struct cifs_tcon *tcon)
 {
        int rc;
+       struct TCP_Server_Info *server = tcon->ses->server;
        struct dfs_cache_tgt_list tl;
        struct dfs_cache_tgt_iterator *it = NULL;
        char *tree;
@@ -141,15 +142,14 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
        if (!tree)
                return -ENOMEM;
 
-       if (tcon->ipc) {
-               scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$",
-                         tcon->ses->server->hostname);
-               rc = CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
-               goto out;
-       }
-
        if (!tcon->dfs_path) {
-               rc = CIFSTCon(0, tcon->ses, tcon->treeName, tcon, nlsc);
+               if (tcon->ipc) {
+                       scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$",
+                                 server->hostname);
+                       rc = CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
+               } else {
+                       rc = CIFSTCon(0, tcon->ses, tcon->treeName, tcon, nlsc);
+               }
                goto out;
        }
 
@@ -157,13 +157,13 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
        if (rc)
                goto out;
 
-       extract_unc_hostname(tcon->ses->server->hostname, &tcp_host,
-                            &tcp_host_len);
+       extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
 
        for (it = dfs_cache_get_tgt_iterator(&tl); it;
             it = dfs_cache_get_next_tgt(&tl, it)) {
                const char *share, *prefix;
                size_t share_len, prefix_len;
+               bool target_match;
 
                rc = dfs_cache_get_tgt_share(it, &share, &share_len, &prefix,
                                             &prefix_len);
@@ -177,19 +177,38 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
 
                if (dfs_host_len != tcp_host_len
                    || strncasecmp(dfs_host, tcp_host, dfs_host_len) != 0) {
-                       cifs_dbg(FYI, "%s: skipping %.*s, doesn't match %.*s",
+                       cifs_dbg(FYI, "%s: %.*s doesn't match %.*s",
                                 __func__,
                                 (int)dfs_host_len, dfs_host,
                                 (int)tcp_host_len, tcp_host);
-                       continue;
-               }
 
-               scnprintf(tree, MAX_TREE_SIZE, "\\%.*s", (int)share_len, share);
+                       rc = match_target_ip(server, dfs_host, dfs_host_len,
+                                            &target_match);
+                       if (rc) {
+                               cifs_dbg(VFS, "%s: failed to match target ip: %d\n",
+                                        __func__, rc);
+                               break;
+                       }
+
+                       if (!target_match) {
+                               cifs_dbg(FYI, "%s: skipping target\n", __func__);
+                               continue;
+                       }
+               }
 
-               rc = CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
-               if (!rc) {
-                       rc = update_super_prepath(tcon, prefix, prefix_len);
-                       break;
+               if (tcon->ipc) {
+                       scnprintf(tree, MAX_TREE_SIZE, "\\\\%.*s\\IPC$",
+                                 (int)share_len, share);
+                       rc = CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
+               } else {
+                       scnprintf(tree, MAX_TREE_SIZE, "\\%.*s", (int)share_len,
+                                 share);
+                       rc = CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
+                       if (!rc) {
+                               rc = update_super_prepath(tcon, prefix,
+                                                         prefix_len);
+                               break;
+                       }
                }
                if (rc == -EREMOTE)
                        break;

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index aa1173f3fb122edf4eb4889042e0f117f2f9c822..ea3189a6ae10c6b3791b2a51511f149c619d51bc 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2496,8 +2496,8 @@ cifs_parse_mount_err:
  * 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)
+bool
+cifs_match_ipaddr(struct sockaddr *srcaddr, struct sockaddr *rhs)
 {
        switch (srcaddr->sa_family) {
        case AF_UNSPEC:
@@ -2588,7 +2588,7 @@ match_address(struct TCP_Server_Info *server, struct sockaddr *addr,
                return false; /* don't expect to be here */
        }
 
-       if (!srcip_matches(srcaddr, (struct sockaddr *)&server->srcaddr))
+       if (!cifs_match_ipaddr(srcaddr, (struct sockaddr *)&server->srcaddr))
                return false;
 
        return true;

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 550ce9020a3eebe8e3cd5a8f216284aa545b024b..1ec6a5543edaa7267409c1d66621e401c712602f 100644 (file)
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -32,6 +32,9 @@
 #include "cifs_unicode.h"
 #include "smb2pdu.h"
 #include "cifsfs.h"
+#ifdef CONFIG_CIFS_DFS_UPCALL
+#include "dns_resolve.h"
+#endif
 
 extern mempool_t *cifs_sm_req_poolp;
 extern mempool_t *cifs_req_poolp;
@@ -1083,6 +1086,51 @@ void cifs_put_tcp_super(struct super_block *sb)
 }
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
+int match_target_ip(struct TCP_Server_Info *server,
+                   const char *share, size_t share_len,
+                   bool *result)
+{
+       int rc;
+       char *target, *tip = NULL;
+       struct sockaddr tipaddr;
+
+       *result = false;
+
+       target = kzalloc(share_len + 3, GFP_KERNEL);
+       if (!target) {
+               rc = -ENOMEM;
+               goto out;
+       }
+
+       scnprintf(target, share_len + 3, "\\\\%.*s", (int)share_len, share);
+
+       cifs_dbg(FYI, "%s: target name: %s\n", __func__, target + 2);
+
+       rc = dns_resolve_server_name_to_ip(target, &tip);
+       if (rc < 0)
+               goto out;
+
+       cifs_dbg(FYI, "%s: target ip: %s\n", __func__, tip);
+
+       if (!cifs_convert_address(&tipaddr, tip, strlen(tip))) {
+               cifs_dbg(VFS, "%s: failed to convert target ip address\n",
+                        __func__);
+               rc = -EINVAL;
+               goto out;
+       }
+
+       *result = cifs_match_ipaddr((struct sockaddr *)&server->dstaddr,
+                                   &tipaddr);
+       cifs_dbg(FYI, "%s: ip addresses match: %u\n", __func__, *result);
+       rc = 0;
+
+out:
+       kfree(target);
+       kfree(tip);
+
+       return rc;
+}
+
 static void tcon_super_cb(struct super_block *sb, void *arg)
 {
        struct super_cb_data *sd = arg;

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index b30aa3cdd845f333304de9fcbdc95f1ae3ec5e99..cabc19f404e65c986ad05c0b78abf64fe4ffab5b 100644 (file)
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -160,6 +160,7 @@ static int __smb2_reconnect(const struct nls_table *nlsc,
                            struct cifs_tcon *tcon)
 {
        int rc;
+       struct TCP_Server_Info *server = tcon->ses->server;
        struct dfs_cache_tgt_list tl;
        struct dfs_cache_tgt_iterator *it = NULL;
        char *tree;
@@ -172,15 +173,15 @@ static int __smb2_reconnect(const struct nls_table *nlsc,
        if (!tree)
                return -ENOMEM;
 
-       if (tcon->ipc) {
-               scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$",
-                         tcon->ses->server->hostname);
-               rc = SMB2_tcon(0, tcon->ses, tree, tcon, nlsc);
-               goto out;
-       }
-
        if (!tcon->dfs_path) {
-               rc = SMB2_tcon(0, tcon->ses, tcon->treeName, tcon, nlsc);
+               if (tcon->ipc) {
+                       scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$",
+                                 server->hostname);
+                       rc = SMB2_tcon(0, tcon->ses, tree, tcon, nlsc);
+               } else {
+                       rc = SMB2_tcon(0, tcon->ses, tcon->treeName, tcon,
+                                      nlsc);
+               }
                goto out;
        }
 
@@ -188,13 +189,13 @@ static int __smb2_reconnect(const struct nls_table *nlsc,
        if (rc)
                goto out;
 
-       extract_unc_hostname(tcon->ses->server->hostname, &tcp_host,
-                            &tcp_host_len);
+       extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
 
        for (it = dfs_cache_get_tgt_iterator(&tl); it;
             it = dfs_cache_get_next_tgt(&tl, it)) {
                const char *share, *prefix;
                size_t share_len, prefix_len;
+               bool target_match;
 
                rc = dfs_cache_get_tgt_share(it, &share, &share_len, &prefix,
                                             &prefix_len);
@@ -208,19 +209,38 @@ static int __smb2_reconnect(const struct nls_table *nlsc,
 
                if (dfs_host_len != tcp_host_len
                    || strncasecmp(dfs_host, tcp_host, dfs_host_len) != 0) {
-                       cifs_dbg(FYI, "%s: skipping %.*s, doesn't match %.*s",
+                       cifs_dbg(FYI, "%s: %.*s doesn't match %.*s",
                                 __func__,
                                 (int)dfs_host_len, dfs_host,
                                 (int)tcp_host_len, tcp_host);
-                       continue;
-               }
 
-               scnprintf(tree, MAX_TREE_SIZE, "\\%.*s", (int)share_len, share);
+                       rc = match_target_ip(server, dfs_host, dfs_host_len,
+                                            &target_match);
+                       if (rc) {
+                               cifs_dbg(VFS, "%s: failed to match target ip: %d\n",
+                                        __func__, rc);
+                               break;
+                       }
 
-               rc = SMB2_tcon(0, tcon->ses, tree, tcon, nlsc);
-               if (!rc) {
-                       rc = update_super_prepath(tcon, prefix, prefix_len);
-                       break;
+                       if (!target_match) {
+                               cifs_dbg(FYI, "%s: skipping target\n", __func__);
+                               continue;
+                       }
+               }
+
+               if (tcon->ipc) {
+                       scnprintf(tree, MAX_TREE_SIZE, "\\\\%.*s\\IPC$",
+                                 (int)share_len, share);
+                       rc = SMB2_tcon(0, tcon->ses, tree, tcon, nlsc);
+               } else {
+                       scnprintf(tree, MAX_TREE_SIZE, "\\%.*s", (int)share_len,
+                                 share);
+                       rc = SMB2_tcon(0, tcon->ses, tree, tcon, nlsc);
+                       if (!rc) {
+                               rc = update_super_prepath(tcon, prefix,
+                                                         prefix_len);
+                               break;
+                       }
                }
                if (rc == -EREMOTE)
                        break;