aboutsummaryrefslogtreecommitdiffstats
path: root/fs/cifs
diff options
context:
space:
mode:
authorJeff Layton <jlayton@redhat.com>2013-09-16 11:23:45 -0400
committerSteve French <smfrench@gmail.com>2013-09-18 11:23:44 -0400
commit9ae6cf606a33b0a762798df0fb742848bcc685b5 (patch)
tree7e6c8e2b5877d89869a997baa7d158943ab42d3e /fs/cifs
parent54afa99057ee2ffd3df0f5e891298bbbb65ea63c (diff)
cifs: stop trying to use virtual circuits
Currently, we try to ensure that we use vcnum of 0 on the first established session on a connection and then try to use a different vcnum on each session after that. This is a little odd, since there's no real reason to use a different vcnum for each SMB session. I can only assume there was some confusion between SMB sessions and VCs. That's somewhat understandable since they both get created during SESSION_SETUP, but the documentation indicates that they are really orthogonal. The comment on max_vcs in particular looks quite misguided. An SMB session is already uniquely identified by the SMB UID value -- there's no need to again uniquely ID with a VC. Furthermore, a vcnum of 0 is a cue to the server that it should release any resources that were previously held by the client. This sounds like a good thing, until you consider that: a) it totally ignores the fact that other programs on the box (e.g. smbclient) might have connections established to the server. Using a vcnum of 0 causes them to get kicked off. b) it causes problems with NAT. If several clients are connected to the same server via the same NAT'ed address, whenever one connects to the server it kicks off all the others, which then reconnect and kick off the first one...ad nauseum. I don't see any reason to ignore the advice in "Implementing CIFS" which has a comprehensive treatment of virtual circuits. In there, it states "...and contrary to the specs the client should always use a VcNumber of one, never zero." Have the client just use a hardcoded vcnum of 1, and stop abusing the special behavior of vcnum 0. Reported-by: Sauron99@gmx.de <sauron99@gmx.de> Signed-off-by: Jeff Layton <jlayton@redhat.com> Reviewed-by: Volker Lendecke <vl@samba.org> Signed-off-by: Steve French <smfrench@gmail.com>
Diffstat (limited to 'fs/cifs')
-rw-r--r--fs/cifs/cifsglob.h4
-rw-r--r--fs/cifs/cifssmb.c1
-rw-r--r--fs/cifs/sess.c84
3 files changed, 1 insertions, 88 deletions
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index cfa14c80ef3b..9c72be6fb0df 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -547,9 +547,6 @@ struct TCP_Server_Info {
547 unsigned int max_rw; /* maxRw specifies the maximum */ 547 unsigned int max_rw; /* maxRw specifies the maximum */
548 /* message size the server can send or receive for */ 548 /* message size the server can send or receive for */
549 /* SMB_COM_WRITE_RAW or SMB_COM_READ_RAW. */ 549 /* SMB_COM_WRITE_RAW or SMB_COM_READ_RAW. */
550 unsigned int max_vcs; /* maximum number of smb sessions, at least
551 those that can be specified uniquely with
552 vcnumbers */
553 unsigned int capabilities; /* selective disabling of caps by smb sess */ 550 unsigned int capabilities; /* selective disabling of caps by smb sess */
554 int timeAdj; /* Adjust for difference in server time zone in sec */ 551 int timeAdj; /* Adjust for difference in server time zone in sec */
555 __u64 CurrentMid; /* multiplex id - rotating counter */ 552 __u64 CurrentMid; /* multiplex id - rotating counter */
@@ -715,7 +712,6 @@ struct cifs_ses {
715 enum statusEnum status; 712 enum statusEnum status;
716 unsigned overrideSecFlg; /* if non-zero override global sec flags */ 713 unsigned overrideSecFlg; /* if non-zero override global sec flags */
717 __u16 ipc_tid; /* special tid for connection to IPC share */ 714 __u16 ipc_tid; /* special tid for connection to IPC share */
718 __u16 vcnum;
719 char *serverOS; /* name of operating system underlying server */ 715 char *serverOS; /* name of operating system underlying server */
720 char *serverNOS; /* name of network operating system of server */ 716 char *serverNOS; /* name of network operating system of server */
721 char *serverDomain; /* security realm of server */ 717 char *serverDomain; /* security realm of server */
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index a3d74fea1623..4baf35949b51 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -463,7 +463,6 @@ decode_lanman_negprot_rsp(struct TCP_Server_Info *server, NEGOTIATE_RSP *pSMBr)
463 cifs_max_pending); 463 cifs_max_pending);
464 set_credits(server, server->maxReq); 464 set_credits(server, server->maxReq);
465 server->maxBuf = le16_to_cpu(rsp->MaxBufSize); 465 server->maxBuf = le16_to_cpu(rsp->MaxBufSize);
466 server->max_vcs = le16_to_cpu(rsp->MaxNumberVcs);
467 /* even though we do not use raw we might as well set this 466 /* even though we do not use raw we might as well set this
468 accurately, in case we ever find a need for it */ 467 accurately, in case we ever find a need for it */
469 if ((le16_to_cpu(rsp->RawMode) & RAW_ENABLE) == RAW_ENABLE) { 468 if ((le16_to_cpu(rsp->RawMode) & RAW_ENABLE) == RAW_ENABLE) {
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 5f99b7f19e78..352358de1d7e 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -32,88 +32,6 @@
32#include <linux/slab.h> 32#include <linux/slab.h>
33#include "cifs_spnego.h" 33#include "cifs_spnego.h"
34 34
35/*
36 * Checks if this is the first smb session to be reconnected after
37 * the socket has been reestablished (so we know whether to use vc 0).
38 * Called while holding the cifs_tcp_ses_lock, so do not block
39 */
40static bool is_first_ses_reconnect(struct cifs_ses *ses)
41{
42 struct list_head *tmp;
43 struct cifs_ses *tmp_ses;
44
45 list_for_each(tmp, &ses->server->smb_ses_list) {
46 tmp_ses = list_entry(tmp, struct cifs_ses,
47 smb_ses_list);
48 if (tmp_ses->need_reconnect == false)
49 return false;
50 }
51 /* could not find a session that was already connected,
52 this must be the first one we are reconnecting */
53 return true;
54}
55
56/*
57 * vc number 0 is treated specially by some servers, and should be the
58 * first one we request. After that we can use vcnumbers up to maxvcs,
59 * one for each smb session (some Windows versions set maxvcs incorrectly
60 * so maxvc=1 can be ignored). If we have too many vcs, we can reuse
61 * any vc but zero (some servers reset the connection on vcnum zero)
62 *
63 */
64static __le16 get_next_vcnum(struct cifs_ses *ses)
65{
66 __u16 vcnum = 0;
67 struct list_head *tmp;
68 struct cifs_ses *tmp_ses;
69 __u16 max_vcs = ses->server->max_vcs;
70 __u16 i;
71 int free_vc_found = 0;
72
73 /* Quoting the MS-SMB specification: "Windows-based SMB servers set this
74 field to one but do not enforce this limit, which allows an SMB client
75 to establish more virtual circuits than allowed by this value ... but
76 other server implementations can enforce this limit." */
77 if (max_vcs < 2)
78 max_vcs = 0xFFFF;
79
80 spin_lock(&cifs_tcp_ses_lock);
81 if ((ses->need_reconnect) && is_first_ses_reconnect(ses))
82 goto get_vc_num_exit; /* vcnum will be zero */
83 for (i = ses->server->srv_count - 1; i < max_vcs; i++) {
84 if (i == 0) /* this is the only connection, use vc 0 */
85 break;
86
87 free_vc_found = 1;
88
89 list_for_each(tmp, &ses->server->smb_ses_list) {
90 tmp_ses = list_entry(tmp, struct cifs_ses,
91 smb_ses_list);
92 if (tmp_ses->vcnum == i) {
93 free_vc_found = 0;
94 break; /* found duplicate, try next vcnum */
95 }
96 }
97 if (free_vc_found)
98 break; /* we found a vcnumber that will work - use it */
99 }
100
101 if (i == 0)
102 vcnum = 0; /* for most common case, ie if one smb session, use
103 vc zero. Also for case when no free vcnum, zero
104 is safest to send (some clients only send zero) */
105 else if (free_vc_found == 0)
106 vcnum = 1; /* we can not reuse vc=0 safely, since some servers
107 reset all uids on that, but 1 is ok. */
108 else
109 vcnum = i;
110 ses->vcnum = vcnum;
111get_vc_num_exit:
112 spin_unlock(&cifs_tcp_ses_lock);
113
114 return cpu_to_le16(vcnum);
115}
116
117static __u32 cifs_ssetup_hdr(struct cifs_ses *ses, SESSION_SETUP_ANDX *pSMB) 35static __u32 cifs_ssetup_hdr(struct cifs_ses *ses, SESSION_SETUP_ANDX *pSMB)
118{ 36{
119 __u32 capabilities = 0; 37 __u32 capabilities = 0;
@@ -128,7 +46,7 @@ static __u32 cifs_ssetup_hdr(struct cifs_ses *ses, SESSION_SETUP_ANDX *pSMB)
128 CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4, 46 CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4,
129 USHRT_MAX)); 47 USHRT_MAX));
130 pSMB->req.MaxMpxCount = cpu_to_le16(ses->server->maxReq); 48 pSMB->req.MaxMpxCount = cpu_to_le16(ses->server->maxReq);
131 pSMB->req.VcNumber = get_next_vcnum(ses); 49 pSMB->req.VcNumber = __constant_cpu_to_le16(1);
132 50
133 /* Now no need to set SMBFLG_CASELESS or obsolete CANONICAL PATH */ 51 /* Now no need to set SMBFLG_CASELESS or obsolete CANONICAL PATH */
134 52