/* multiplexed reads or writes */
        unsigned int maxBuf;    /* maxBuf specifies the maximum */
        /* message size the server can send or receive for non-raw SMBs */
-       unsigned int maxRw;     /* maxRw specifies the maximum */
+       unsigned int max_rw;    /* maxRw specifies the maximum */
        /* message size the server can send or receive for */
        /* SMB_COM_WRITE_RAW or SMB_COM_READ_RAW. */
+       unsigned int max_vcs;   /* maximum number of smb sessions, at least
+                                  those that can be specified uniquely with
+                                  vcnumbers */
        char sessid[4];         /* unique token id for this session */
        /* (returned on Negotiate */
        int capabilities; /* allow selective disabling of caps by smb sess */
        unsigned overrideSecFlg;  /* if non-zero override global sec flags */
        __u16 ipc_tid;          /* special tid for connection to IPC share */
        __u16 flags;
+       __u16 vcnum;
        char *serverOS;         /* name of operating system underlying server */
        char *serverNOS;        /* name of network operating system of server */
        char *serverDomain;     /* security realm of server */
 
                server->maxReq = le16_to_cpu(rsp->MaxMpxCount);
                server->maxBuf = min((__u32)le16_to_cpu(rsp->MaxBufSize),
                                (__u32)CIFSMaxBufSize + MAX_CIFS_HDR_SIZE);
+               server->max_vcs = le16_to_cpu(rsp->MaxNumberVcs);
                GETU32(server->sessid) = le32_to_cpu(rsp->SessionKey);
                /* even though we do not use raw we might as well set this
                accurately, in case we ever find a need for it */
                if ((le16_to_cpu(rsp->RawMode) & RAW_ENABLE) == RAW_ENABLE) {
-                       server->maxRw = 0xFF00;
+                       server->max_rw = 0xFF00;
                        server->capabilities = CAP_MPX_MODE | CAP_RAW_MODE;
                } else {
-                       server->maxRw = 0;/* we do not need to use raw anyway */
+                       server->max_rw = 0;/* do not need to use raw anyway */
                        server->capabilities = CAP_MPX_MODE;
                }
                tmp = (__s16)le16_to_cpu(rsp->ServerTimeZone);
        /* probably no need to store and check maxvcs */
        server->maxBuf = min(le32_to_cpu(pSMBr->MaxBufferSize),
                        (__u32) CIFSMaxBufSize + MAX_CIFS_HDR_SIZE);
-       server->maxRw = le32_to_cpu(pSMBr->MaxRawSize);
+       server->max_rw = le32_to_cpu(pSMBr->MaxRawSize);
        cFYI(DBG2, ("Max buf = %d", ses->server->maxBuf));
        GETU32(ses->server->sessid) = le32_to_cpu(pSMBr->SessionKey);
        server->capabilities = le32_to_cpu(pSMBr->Capabilities);
 
 extern void SMBNTencrypt(unsigned char *passwd, unsigned char *c8,
                         unsigned char *p24);
 
+/* Checks if this is the first smb session to be reconnected after
+   the socket has been reestablished (so we know whether to use vc 0).
+   Called while holding the cifs_tcp_ses_lock, so do not block */
+static bool is_first_ses_reconnect(struct cifsSesInfo *ses)
+{
+       struct list_head *tmp;
+       struct cifsSesInfo *tmp_ses;
+
+       list_for_each(tmp, &ses->server->smb_ses_list) {
+               tmp_ses = list_entry(tmp, struct cifsSesInfo,
+                                    smb_ses_list);
+               if (tmp_ses->need_reconnect == false)
+                       return false;
+       }
+       /* could not find a session that was already connected,
+          this must be the first one we are reconnecting */
+       return true;
+}
+
+/*
+ *     vc number 0 is treated specially by some servers, and should be the
+ *      first one we request.  After that we can use vcnumbers up to maxvcs,
+ *     one for each smb session (some Windows versions set maxvcs incorrectly
+ *     so maxvc=1 can be ignored).  If we have too many vcs, we can reuse
+ *     any vc but zero (some servers reset the connection on vcnum zero)
+ *
+ */
+static __le16 get_next_vcnum(struct cifsSesInfo *ses)
+{
+       __u16 vcnum = 0;
+       struct list_head *tmp;
+       struct cifsSesInfo *tmp_ses;
+       __u16 max_vcs = ses->server->max_vcs;
+       __u16 i;
+       int free_vc_found = 0;
+
+       /* Quoting the MS-SMB specification: "Windows-based SMB servers set this
+       field to one but do not enforce this limit, which allows an SMB client
+       to establish more virtual circuits than allowed by this value ... but
+       other server implementations can enforce this limit." */
+       if (max_vcs < 2)
+               max_vcs = 0xFFFF;
+
+       write_lock(&cifs_tcp_ses_lock);
+       if ((ses->need_reconnect) && is_first_ses_reconnect(ses))
+                       goto get_vc_num_exit;  /* vcnum will be zero */
+       for (i = ses->server->srv_count - 1; i < max_vcs; i++) {
+               if (i == 0) /* this is the only connection, use vc 0 */
+                       break;
+
+               free_vc_found = 1;
+
+               list_for_each(tmp, &ses->server->smb_ses_list) {
+                       tmp_ses = list_entry(tmp, struct cifsSesInfo,
+                                            smb_ses_list);
+                       if (tmp_ses->vcnum == i) {
+                               free_vc_found = 0;
+                               break; /* found duplicate, try next vcnum */
+                       }
+               }
+               if (free_vc_found)
+                       break; /* we found a vcnumber that will work - use it */
+       }
+
+       if (i == 0)
+               vcnum = 0; /* for most common case, ie if one smb session, use
+                             vc zero.  Also for case when no free vcnum, zero
+                             is safest to send (some clients only send zero) */
+       else if (free_vc_found == 0)
+               vcnum = 1;  /* we can not reuse vc=0 safely, since some servers
+                               reset all uids on that, but 1 is ok. */
+       else
+               vcnum = i;
+       ses->vcnum = vcnum;
+get_vc_num_exit:
+       write_unlock(&cifs_tcp_ses_lock);
+
+       return le16_to_cpu(vcnum);
+}
+
 static __u32 cifs_ssetup_hdr(struct cifsSesInfo *ses, SESSION_SETUP_ANDX *pSMB)
 {
        __u32 capabilities = 0;
 
        /* init fields common to all four types of SessSetup */
-       /* note that header is initialized to zero in header_assemble */
+       /* Note that offsets for first seven fields in req struct are same  */
+       /*      in CIFS Specs so does not matter which of 3 forms of struct */
+       /*      that we use in next few lines                               */
+       /* Note that header is initialized to zero in header_assemble */
        pSMB->req.AndXCommand = 0xFF;
        pSMB->req.MaxBufferSize = cpu_to_le16(ses->server->maxBuf);
        pSMB->req.MaxMpxCount = cpu_to_le16(ses->server->maxReq);
+       pSMB->req.VcNumber = get_next_vcnum(ses);
 
        /* Now no need to set SMBFLG_CASELESS or obsolete CANONICAL PATH */
 
        if (ses->capabilities & CAP_UNIX)
                capabilities |= CAP_UNIX;
 
-       /* BB check whether to init vcnum BB */
        return capabilities;
 }