[PATCH 1/3] cifs: set up next DFS target before generic_ip_connect()

[PATCH 1/3] cifs: set up next DFS target before generic_ip_connect()

[Paulo Alcantara]

If we mount a very specific DFS link

    \\FS0.FOO.COM\dfs\link -> \FS0\share1, \FS1\share2

where its target list contains NB names ("FS0" & "FS1") rather than
FQDN ones ("FS0.FOO.COM" & "FS1.FOO.COM"), we end up connecting to
\FOO\share1 but server->hostname will have "FOO.COM".  The reason is
because both "FS0" and "FS0.FOO.COM" resolve to same IP address and
they share same TCP server connection, but "FS0.FOO.COM" was the first
hostname set -- which is OK.

However, if the echo thread timeouts and we still have a good
connection to "FS0", in cifs_reconnect()

    rc = generic_ip_connect(server) -> success
    if (rc) {
            ...
            reconn_inval_dfs_target(server, cifs_sb, &tgt_list,
	                            &tgt_it);
            ...
     }
     ...

it successfully reconnects to "FS0" server but does not set up next
DFS target - which should be the same target server "\FS0\share1" -
and server->hostname remains set to "FS0.FOO.COM" rather than "FS0",
as reconn_inval_dfs_target() would have it set to "FS0" if called
earlier.

Finally, in __smb2_reconnect(), the reconnect of tcons would fail
because tcon->ses->server->hostname (FS0.FOO.COM) does not match DFS
target's hostname (FS0).

Fix that by calling reconn_inval_dfs_target() before
generic_ip_connect() so server->hostname will get updated correctly
prior to reconnecting its tcons in __smb2_reconnect().

With "cifs: handle hostnames that resolve to same ip in failover"
patch

    - The above problem would not occur.
    - We could save an DNS query to find out that they both resolve to
      the same ip address.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
---
 fs/cifs/connect.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 28268ed461b8..47b9fbb70bf5 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -572,26 +572,26 @@ cifs_reconnect(struct TCP_Server_Info *server)
 		try_to_freeze();
 
 		mutex_lock(&server->srv_mutex);
+#ifdef CONFIG_CIFS_DFS_UPCALL
 		/*
 		 * Set up next DFS target server (if any) for reconnect. If DFS
 		 * feature is disabled, then we will retry last server we
 		 * connected to before.
 		 */
+		reconn_inval_dfs_target(server, cifs_sb, &tgt_list, &tgt_it);
+#endif
+		rc = reconn_set_ipaddr(server);
+		if (rc) {
+			cifs_dbg(FYI, "%s: failed to resolve hostname: %d\n",
+				 __func__, rc);
+		}
+
 		if (cifs_rdma_enabled(server))
 			rc = smbd_reconnect(server);
 		else
 			rc = generic_ip_connect(server);
 		if (rc) {
 			cifs_dbg(FYI, "reconnect error %d\n", rc);
-#ifdef CONFIG_CIFS_DFS_UPCALL
-			reconn_inval_dfs_target(server, cifs_sb, &tgt_list,
-						&tgt_it);
-#endif
-			rc = reconn_set_ipaddr(server);
-			if (rc) {
-				cifs_dbg(FYI, "%s: failed to resolve hostname: %d\n",
-					 __func__, rc);
-			}
 			mutex_unlock(&server->srv_mutex);
 			msleep(3000);
 		} else {
-- 
2.26.2

[PATCH 2/3] cifs: handle hostnames that resolve to same ip in failover

[Paulo Alcantara]

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>
---
 fs/cifs/cifsproto.h |  5 ++++
 fs/cifs/cifssmb.c   | 55 +++++++++++++++++++++++++++++---------------
 fs/cifs/connect.c   |  6 ++---
 fs/cifs/misc.c      | 48 ++++++++++++++++++++++++++++++++++++++
 fs/cifs/smb2pdu.c   | 56 ++++++++++++++++++++++++++++++---------------
 5 files changed, 131 insertions(+), 39 deletions(-)

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 12a895e02db4..311d8e86c5a8 100644
--- 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 182b864b3075..526171503c4e 100644
--- 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;
+
+			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;
+			}
 		}
 
-		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 (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 47b9fbb70bf5..094c939cb98e 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2496,8 +2496,8 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
  * 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 550ce9020a3e..1ec6a5543eda 100644
--- 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 b30aa3cdd845..cabc19f404e6 100644
--- 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;
+
+			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;
+			}
 		}
 
-		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 (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;
-- 
2.26.2

Re: [PATCH 2/3] cifs: handle hostnames that resolve to same ip in failover

[Aurélien Aptel]

Reviewed-by: Aurelien Aptel <aaptel@suse.com>

-- 
Aurélien Aptel / SUSE Labs Samba Team
GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)

Re: [PATCH 2/3] cifs: handle hostnames that resolve to same ip in failover

[Steve French]

merged all 3 into cifs-2.6.git for-next

thx

On Thu, May 28, 2020 at 10:29 AM Aurélien Aptel <aaptel@suse.com> wrote:
>
>
> Reviewed-by: Aurelien Aptel <aaptel@suse.com>
>
> --
> Aurélien Aptel / SUSE Labs Samba Team
> GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3
> SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
> GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)



-- 
Thanks,

Steve

[PATCH 3/3] cifs: get rid of unused parameter in reconn_setup_dfs_targets()

[Paulo Alcantara]

The target iterator parameter "it" is not used in
reconn_setup_dfs_targets(), so just remove it.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
---
 fs/cifs/connect.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 094c939cb98e..3373c4a72cf4 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -426,8 +426,7 @@ static void reconn_inval_dfs_target(struct TCP_Server_Info *server,
 }
 
 static inline int reconn_setup_dfs_targets(struct cifs_sb_info *cifs_sb,
-					   struct dfs_cache_tgt_list *tl,
-					   struct dfs_cache_tgt_iterator **it)
+					   struct dfs_cache_tgt_list *tl)
 {
 	if (!cifs_sb->origin_fullpath)
 		return -EOPNOTSUPP;
@@ -472,7 +471,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 	} else {
 		cifs_sb = CIFS_SB(sb);
 
-		rc = reconn_setup_dfs_targets(cifs_sb, &tgt_list, &tgt_it);
+		rc = reconn_setup_dfs_targets(cifs_sb, &tgt_list);
 		if (rc && (rc != -EOPNOTSUPP)) {
 			cifs_server_dbg(VFS, "%s: no target servers for DFS failover\n",
 				 __func__);
-- 
2.26.2

Re: [PATCH 3/3] cifs: get rid of unused parameter in reconn_setup_dfs_targets()

[Aurélien Aptel]

Reviewed-by: Aurelien Aptel <aaptel@suse.com>

-- 
Aurélien Aptel / SUSE Labs Samba Team
GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)

Re: [PATCH 1/3] cifs: set up next DFS target before generic_ip_connect()

[Aurélien Aptel]

Reviewed-by: Aurelien Aptel <aaptel@suse.com>

-- 
Aurélien Aptel / SUSE Labs Samba Team
GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)