/*
 *   fs/cifs/smb2pdu.c
 *
 *   Copyright (C) International Business Machines  Corp., 2009, 2011
 *                 Etersoft, 2012
 *   Author(s): Steve French (sfrench@us.ibm.com)
 *              Pavel Shilovsky (pshilovsky@samba.org) 2012
 *
 *   Contains the routines for constructing the SMB2 PDUs themselves
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published
 *   by the Free Software Foundation; either version 2.1 of the License, or
 *   (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with this library; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

 /* SMB2 PDU handling routines here - except for leftovers (eg session setup) */
 /* Note that there are handle based routines which must be                   */
 /* treated slightly differently for reconnection purposes since we never     */
 /* want to reuse a stale file handle and only the caller knows the file info */

#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/vfs.h>
#include <linux/uaccess.h>
#include <linux/xattr.h>
#include "smb2pdu.h"
#include "cifsglob.h"
#include "cifsacl.h"
#include "cifsproto.h"
#include "smb2proto.h"
#include "cifs_unicode.h"
#include "cifs_debug.h"
#include "ntlmssp.h"
#include "smb2status.h"

/*
 *  The following table defines the expected "StructureSize" of SMB2 requests
 *  in order by SMB2 command.  This is similar to "wct" in SMB/CIFS requests.
 *
 *  Note that commands are defined in smb2pdu.h in le16 but the array below is
 *  indexed by command in host byte order.
 */
static const int smb2_req_struct_sizes[NUMBER_OF_SMB2_COMMANDS] = {
        /* SMB2_NEGOTIATE */ 36,
        /* SMB2_SESSION_SETUP */ 25,
        /* SMB2_LOGOFF */ 4,
        /* SMB2_TREE_CONNECT */ 9,
        /* SMB2_TREE_DISCONNECT */ 4,
        /* SMB2_CREATE */ 57,
        /* SMB2_CLOSE */ 24,
        /* SMB2_FLUSH */ 24,
        /* SMB2_READ */ 49,
        /* SMB2_WRITE */ 49,
        /* SMB2_LOCK */ 48,
        /* SMB2_IOCTL */ 57,
        /* SMB2_CANCEL */ 4,
        /* SMB2_ECHO */ 4,
        /* SMB2_QUERY_DIRECTORY */ 33,
        /* SMB2_CHANGE_NOTIFY */ 32,
        /* SMB2_QUERY_INFO */ 41,
        /* SMB2_SET_INFO */ 33,
        /* SMB2_OPLOCK_BREAK */ 24 /* BB this is 36 for LEASE_BREAK variant */
};


static void
smb2_hdr_assemble(struct smb2_hdr *hdr, __le16 smb2_cmd /* command */ ,
                  const struct cifs_tcon *tcon)
{
        struct smb2_pdu *pdu = (struct smb2_pdu *)hdr;
        char *temp = (char *)hdr;
        /* lookup word count ie StructureSize from table */
        __u16 parmsize = smb2_req_struct_sizes[le16_to_cpu(smb2_cmd)];

        /*
         * smaller than SMALL_BUFFER_SIZE but bigger than fixed area of
         * largest operations (Create)
         */
        memset(temp, 0, 256);

        /* Note this is only network field converted to big endian */
        hdr->smb2_buf_length = cpu_to_be32(parmsize + sizeof(struct smb2_hdr)
                        - 4 /*  RFC 1001 length field itself not counted */);

        hdr->ProtocolId[0] = 0xFE;
        hdr->ProtocolId[1] = 'S';
        hdr->ProtocolId[2] = 'M';
        hdr->ProtocolId[3] = 'B';
        hdr->StructureSize = cpu_to_le16(64);
        hdr->Command = smb2_cmd;
        hdr->CreditRequest = cpu_to_le16(2); /* BB make this dynamic */
        hdr->ProcessId = cpu_to_le32((__u16)current->tgid);

        if (!tcon)
                goto out;

        hdr->TreeId = tcon->tid;
        /* Uid is not converted */
        if (tcon->ses)
                hdr->SessionId = tcon->ses->Suid;
        /* BB check following DFS flags BB */
        /* BB do we have to add check for SHI1005_FLAGS_DFS_ROOT too? */
        if (tcon->share_flags & SHI1005_FLAGS_DFS)
                hdr->Flags |= SMB2_FLAGS_DFS_OPERATIONS;
        /* BB how does SMB2 do case sensitive? */
        /* if (tcon->nocase)
                hdr->Flags |= SMBFLG_CASELESS; */
        /* if (tcon->ses && tcon->ses->server &&
            (tcon->ses->server->sec_mode & SECMODE_SIGN_REQUIRED))
                hdr->Flags |= SMB2_FLAGS_SIGNED; */
out:
        pdu->StructureSize2 = cpu_to_le16(parmsize);
        return;
}

static int
smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
{
        int rc = 0;
        struct nls_table *nls_codepage;
        struct cifs_ses *ses;
        struct TCP_Server_Info *server;

        /*
         * SMB2s NegProt, SessSetup, Logoff do not have tcon yet so
         * check for tcp and smb session status done differently
         * for those three - in the calling routine.
         */
        if (tcon == NULL)
                return rc;

        if (smb2_command == SMB2_TREE_CONNECT)
                return rc;

        if (tcon->tidStatus == CifsExiting) {
                /*
                 * only tree disconnect, open, and write,
                 * (and ulogoff which does not have tcon)
                 * are allowed as we start force umount.
                 */
                if ((smb2_command != SMB2_WRITE) &&
                   (smb2_command != SMB2_CREATE) &&
                   (smb2_command != SMB2_TREE_DISCONNECT)) {
                        cFYI(1, "can not send cmd %d while umounting",
                                smb2_command);
                        return -ENODEV;
                }
        }
        if ((!tcon->ses) || (tcon->ses->status == CifsExiting) ||
            (!tcon->ses->server))
                return -EIO;

        ses = tcon->ses;
        server = ses->server;

        /*
         * Give demultiplex thread up to 10 seconds to reconnect, should be
         * greater than cifs socket timeout which is 7 seconds
         */
        while (server->tcpStatus == CifsNeedReconnect) {
                /*
                 * Return to caller for TREE_DISCONNECT and LOGOFF and CLOSE
                 * here since they are implicitly done when session drops.
                 */
                switch (smb2_command) {
                /*
                 * BB Should we keep oplock break and add flush to exceptions?
                 */
                case SMB2_TREE_DISCONNECT:
                case SMB2_CANCEL:
                case SMB2_CLOSE:
                case SMB2_OPLOCK_BREAK:
                        return -EAGAIN;
                }

                wait_event_interruptible_timeout(server->response_q,
                        (server->tcpStatus != CifsNeedReconnect), 10 * HZ);

                /* are we still trying to reconnect? */
                if (server->tcpStatus != CifsNeedReconnect)
                        break;

                /*
                 * on "soft" mounts we wait once. Hard mounts keep
                 * retrying until process is killed or server comes
                 * back on-line
                 */
                if (!tcon->retry) {
                        cFYI(1, "gave up waiting on reconnect in smb_init");
                        return -EHOSTDOWN;
                }
        }

        if (!tcon->ses->need_reconnect && !tcon->need_reconnect)
                return rc;

        nls_codepage = load_nls_default();

        /*
         * need to prevent multiple threads trying to simultaneously reconnect
         * the same SMB session
         */
        mutex_lock(&tcon->ses->session_mutex);
        rc = cifs_negotiate_protocol(0, tcon->ses);
        if (!rc && tcon->ses->need_reconnect)
                rc = cifs_setup_session(0, tcon->ses, nls_codepage);

        if (rc || !tcon->need_reconnect) {
                mutex_unlock(&tcon->ses->session_mutex);
                goto out;
        }

        cifs_mark_open_files_invalid(tcon);
        rc = SMB2_tcon(0, tcon->ses, tcon->treeName, tcon, nls_codepage);
        mutex_unlock(&tcon->ses->session_mutex);
        cFYI(1, "reconnect tcon rc = %d", rc);
        if (rc)
                goto out;
        atomic_inc(&tconInfoReconnectCount);
        /*
         * BB FIXME add code to check if wsize needs update due to negotiated
         * smb buffer size shrinking.
         */
out:
        /*
         * Check if handle based operation so we know whether we can continue
         * or not without returning to caller to reset file handle.
         */
        /*
         * BB Is flush done by server on drop of tcp session? Should we special
         * case it and skip above?
         */
        switch (smb2_command) {
        case SMB2_FLUSH:
        case SMB2_READ:
        case SMB2_WRITE:
        case SMB2_LOCK:
        case SMB2_IOCTL:
        case SMB2_QUERY_DIRECTORY:
        case SMB2_CHANGE_NOTIFY:
        case SMB2_QUERY_INFO:
        case SMB2_SET_INFO:
                return -EAGAIN;
        }
        unload_nls(nls_codepage);
        return rc;
}

/*
 * Allocate and return pointer to an SMB request hdr, and set basic
 * SMB information in the SMB header. If the return code is zero, this
 * function must have filled in request_buf pointer.
 */
static int
small_smb2_init(__le16 smb2_command, struct cifs_tcon *tcon,
                void **request_buf)
{
        int rc = 0;

        rc = smb2_reconnect(smb2_command, tcon);
        if (rc)
                return rc;

        /* BB eventually switch this to SMB2 specific small buf size */
        *request_buf = cifs_small_buf_get();
        if (*request_buf == NULL) {
                /* BB should we add a retry in here if not a writepage? */
                return -ENOMEM;
        }

        smb2_hdr_assemble((struct smb2_hdr *) *request_buf, smb2_command, tcon);

        if (tcon != NULL) {
#ifdef CONFIG_CIFS_STATS2
                uint16_t com_code = le16_to_cpu(smb2_command);
                cifs_stats_inc(&tcon->stats.smb2_stats.smb2_com_sent[com_code]);
#endif
                cifs_stats_inc(&tcon->num_smbs_sent);
        }

        return rc;
}

static void
free_rsp_buf(int resp_buftype, void *rsp)
{
        if (resp_buftype == CIFS_SMALL_BUFFER)
                cifs_small_buf_release(rsp);
        else if (resp_buftype == CIFS_LARGE_BUFFER)
                cifs_buf_release(rsp);
}

#define SMB2_NUM_PROT 1

#define SMB2_PROT   0
#define SMB21_PROT  1
#define BAD_PROT 0xFFFF

#define SMB2_PROT_ID  0x0202
#define SMB21_PROT_ID 0x0210
#define BAD_PROT_ID   0xFFFF

static struct {
        int index;
        __le16 name;
} smb2protocols[] = {
        {SMB2_PROT,  cpu_to_le16(SMB2_PROT_ID)},
        {SMB21_PROT, cpu_to_le16(SMB21_PROT_ID)},
        {BAD_PROT,   cpu_to_le16(BAD_PROT_ID)}
};

/*
 *
 *      SMB2 Worker functions follow:
 *
 *      The general structure of the worker functions is:
 *      1) Call smb2_init (assembles SMB2 header)
 *      2) Initialize SMB2 command specific fields in fixed length area of SMB
 *      3) Call smb_sendrcv2 (sends request on socket and waits for response)
 *      4) Decode SMB2 command specific fields in the fixed length area
 *      5) Decode variable length data area (if any for this SMB2 command type)
 *      6) Call free smb buffer
 *      7) return
 *
 */

int
SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
{
        struct smb2_negotiate_req *req;
        struct smb2_negotiate_rsp *rsp;
        struct kvec iov[1];
        int rc = 0;
        int resp_buftype;
        struct TCP_Server_Info *server;
        unsigned int sec_flags;
        u16 i;
        u16 temp = 0;
        int blob_offset, blob_length;
        char *security_blob;
        int flags = CIFS_NEG_OP;

        cFYI(1, "Negotiate protocol");

        if (ses->server)
                server = ses->server;
        else {
                rc = -EIO;
                return rc;
        }

        rc = small_smb2_init(SMB2_NEGOTIATE, NULL, (void **) &req);
        if (rc)
                return rc;

        /* if any of auth flags (ie not sign or seal) are overriden use them */
        if (ses->overrideSecFlg & (~(CIFSSEC_MUST_SIGN | CIFSSEC_MUST_SEAL)))
                sec_flags = ses->overrideSecFlg;  /* BB FIXME fix sign flags?*/
        else /* if override flags set only sign/seal OR them with global auth */
                sec_flags = global_secflags | ses->overrideSecFlg;

        cFYI(1, "sec_flags 0x%x", sec_flags);

        req->hdr.SessionId = 0;

        for (i = 0; i < SMB2_NUM_PROT; i++)
                req->Dialects[i] = smb2protocols[i].name;

        req->DialectCount = cpu_to_le16(i);
        inc_rfc1001_len(req, i * 2);

        /* only one of SMB2 signing flags may be set in SMB2 request */
        if ((sec_flags & CIFSSEC_MUST_SIGN) == CIFSSEC_MUST_SIGN)
                temp = SMB2_NEGOTIATE_SIGNING_REQUIRED;
        else if (sec_flags & CIFSSEC_MAY_SIGN) /* MAY_SIGN is a single flag */
                temp = SMB2_NEGOTIATE_SIGNING_ENABLED;

        req->SecurityMode = cpu_to_le16(temp);

        req->Capabilities = cpu_to_le32(SMB2_GLOBAL_CAP_DFS);

        iov[0].iov_base = (char *)req;
        /* 4 for rfc1002 length field */
        iov[0].iov_len = get_rfc1002_length(req) + 4;

        rc = SendReceive2(xid, ses, iov, 1, &resp_buftype, flags);

        rsp = (struct smb2_negotiate_rsp *)iov[0].iov_base;
        /*
         * No tcon so can't do
         * cifs_stats_inc(&tcon->stats.smb2_stats.smb2_com_fail[SMB2...]);
         */
        if (rc != 0)
                goto neg_exit;

        if (rsp == NULL) {
                rc = -EIO;
                goto neg_exit;
        }

        cFYI(1, "mode 0x%x", rsp->SecurityMode);

        if (rsp->DialectRevision == smb2protocols[SMB21_PROT].name)
                cFYI(1, "negotiated smb2.1 dialect");
        else if (rsp->DialectRevision == smb2protocols[SMB2_PROT].name)
                cFYI(1, "negotiated smb2 dialect");
        else {
                cERROR(1, "Illegal dialect returned by server %d",
                           le16_to_cpu(rsp->DialectRevision));
                rc = -EIO;
                goto neg_exit;
        }
        server->dialect = le16_to_cpu(rsp->DialectRevision);

        server->maxBuf = le32_to_cpu(rsp->MaxTransactSize);
        server->max_read = le32_to_cpu(rsp->MaxReadSize);
        server->max_write = le32_to_cpu(rsp->MaxWriteSize);
        /* BB Do we need to validate the SecurityMode? */
        server->sec_mode = le16_to_cpu(rsp->SecurityMode);
        server->capabilities = le32_to_cpu(rsp->Capabilities);
        /* Internal types */
        server->capabilities |= SMB2_NT_FIND | SMB2_LARGE_FILES;

        security_blob = smb2_get_data_area_len(&blob_offset, &blob_length,
                                               &rsp->hdr);
        if (blob_length == 0) {
                cERROR(1, "missing security blob on negprot");
                rc = -EIO;
                goto neg_exit;
        }
#ifdef CONFIG_SMB2_ASN1  /* BB REMOVEME when updated asn1.c ready */
        rc = decode_neg_token_init(security_blob, blob_length,
                                   &server->sec_type);
        if (rc == 1)
                rc = 0;
        else if (rc == 0) {
                rc = -EIO;
                goto neg_exit;
        }
#endif

neg_exit:
        free_rsp_buf(resp_buftype, rsp);
        return rc;
}

int
SMB2_sess_setup(const unsigned int xid, struct cifs_ses *ses,
                const struct nls_table *nls_cp)
{
        struct smb2_sess_setup_req *req;
        struct smb2_sess_setup_rsp *rsp = NULL;
        struct kvec iov[2];
        int rc = 0;
        int resp_buftype;
        __le32 phase = NtLmNegotiate; /* NTLMSSP, if needed, is multistage */
        struct TCP_Server_Info *server;
        unsigned int sec_flags;
        u8 temp = 0;
        u16 blob_length = 0;
        char *security_blob;
        char *ntlmssp_blob = NULL;
        bool use_spnego = false; /* else use raw ntlmssp */

        cFYI(1, "Session Setup");

        if (ses->server)
                server = ses->server;
        else {
                rc = -EIO;
                return rc;
        }

        /*
         * If memory allocation is successful, caller of this function
         * frees it.
         */
        ses->ntlmssp = kmalloc(sizeof(struct ntlmssp_auth), GFP_KERNEL);
        if (!ses->ntlmssp)
                return -ENOMEM;

        ses->server->secType = RawNTLMSSP;

ssetup_ntlmssp_authenticate:
        if (phase == NtLmChallenge)
                phase = NtLmAuthenticate; /* if ntlmssp, now final phase */

        rc = small_smb2_init(SMB2_SESSION_SETUP, NULL, (void **) &req);
        if (rc)
                return rc;

        /* if any of auth flags (ie not sign or seal) are overriden use them */
        if (ses->overrideSecFlg & (~(CIFSSEC_MUST_SIGN | CIFSSEC_MUST_SEAL)))
                sec_flags = ses->overrideSecFlg;  /* BB FIXME fix sign flags?*/
        else /* if override flags set only sign/seal OR them with global auth */
                sec_flags = global_secflags | ses->overrideSecFlg;

        cFYI(1, "sec_flags 0x%x", sec_flags);

        req->hdr.SessionId = 0; /* First session, not a reauthenticate */
        req->VcNumber = 0; /* MBZ */
        /* to enable echos and oplocks */
        req->hdr.CreditRequest = cpu_to_le16(3);

        /* only one of SMB2 signing flags may be set in SMB2 request */
        if ((sec_flags & CIFSSEC_MUST_SIGN) == CIFSSEC_MUST_SIGN)
                temp = SMB2_NEGOTIATE_SIGNING_REQUIRED;
        else if (ses->server->sec_mode & SMB2_NEGOTIATE_SIGNING_REQUIRED)
                temp = SMB2_NEGOTIATE_SIGNING_REQUIRED;
        else if (sec_flags & CIFSSEC_MAY_SIGN) /* MAY_SIGN is a single flag */
                temp = SMB2_NEGOTIATE_SIGNING_ENABLED;

        req->SecurityMode = temp;
        req->Capabilities = 0;
        req->Channel = 0; /* MBZ */

        iov[0].iov_base = (char *)req;
        /* 4 for rfc1002 length field and 1 for pad */
        iov[0].iov_len = get_rfc1002_length(req) + 4 - 1;
        if (phase == NtLmNegotiate) {
                ntlmssp_blob = kmalloc(sizeof(struct _NEGOTIATE_MESSAGE),
                                       GFP_KERNEL);
                if (ntlmssp_blob == NULL) {
                        rc = -ENOMEM;
                        goto ssetup_exit;
                }
                build_ntlmssp_negotiate_blob(ntlmssp_blob, ses);
                if (use_spnego) {
                        /* blob_length = build_spnego_ntlmssp_blob(
                                        &security_blob,
                                        sizeof(struct _NEGOTIATE_MESSAGE),
                                        ntlmssp_blob); */
                        /* BB eventually need to add this */
                        cERROR(1, "spnego not supported for SMB2 yet");
                        rc = -EOPNOTSUPP;
                        kfree(ntlmssp_blob);
                        goto ssetup_exit;
                } else {
                        blob_length = sizeof(struct _NEGOTIATE_MESSAGE);
                        /* with raw NTLMSSP we don't encapsulate in SPNEGO */
                        security_blob = ntlmssp_blob;
                }
        } else if (phase == NtLmAuthenticate) {
                req->hdr.SessionId = ses->Suid;
                ntlmssp_blob = kzalloc(sizeof(struct _NEGOTIATE_MESSAGE) + 500,
                                       GFP_KERNEL);
                if (ntlmssp_blob == NULL) {
                        cERROR(1, "failed to malloc ntlmssp blob");
                        rc = -ENOMEM;
                        goto ssetup_exit;
                }
                rc = build_ntlmssp_auth_blob(ntlmssp_blob, &blob_length, ses,
                                             nls_cp);
                if (rc) {
                        cFYI(1, "build_ntlmssp_auth_blob failed %d", rc);
                        goto ssetup_exit; /* BB double check error handling */
                }
                if (use_spnego) {
                        /* blob_length = build_spnego_ntlmssp_blob(
                                                        &security_blob,
                                                        blob_length,
                                                        ntlmssp_blob); */
                        cERROR(1, "spnego not supported for SMB2 yet");
                        rc = -EOPNOTSUPP;
                        kfree(ntlmssp_blob);
                        goto ssetup_exit;
                } else {
                        security_blob = ntlmssp_blob;
                }
        } else {
                cERROR(1, "illegal ntlmssp phase");
                rc = -EIO;
                goto ssetup_exit;
        }

        /* Testing shows that buffer offset must be at location of Buffer[0] */
        req->SecurityBufferOffset =
                                cpu_to_le16(sizeof(struct smb2_sess_setup_req) -
                                            1 /* pad */ - 4 /* rfc1001 len */);
        req->SecurityBufferLength = cpu_to_le16(blob_length);
        iov[1].iov_base = security_blob;
        iov[1].iov_len = blob_length;

        inc_rfc1001_len(req, blob_length - 1 /* pad */);

        /* BB add code to build os and lm fields */

        rc = SendReceive2(xid, ses, iov, 2, &resp_buftype, CIFS_LOG_ERROR);

        kfree(security_blob);
        rsp = (struct smb2_sess_setup_rsp *)iov[0].iov_base;
        if (rsp->hdr.Status == STATUS_MORE_PROCESSING_REQUIRED) {
                if (phase != NtLmNegotiate) {
                        cERROR(1, "Unexpected more processing error");
                        goto ssetup_exit;
                }
                if (offsetof(struct smb2_sess_setup_rsp, Buffer) - 4 !=
                        le16_to_cpu(rsp->SecurityBufferOffset)) {
                        cERROR(1, "Invalid security buffer offset %d",
                                  le16_to_cpu(rsp->SecurityBufferOffset));
                        rc = -EIO;
                        goto ssetup_exit;
                }

                /* NTLMSSP Negotiate sent now processing challenge (response) */
                phase = NtLmChallenge; /* process ntlmssp challenge */
                rc = 0; /* MORE_PROCESSING is not an error here but expected */
                ses->Suid = rsp->hdr.SessionId;
                rc = decode_ntlmssp_challenge(rsp->Buffer,
                                le16_to_cpu(rsp->SecurityBufferLength), ses);
        }

        /*
         * BB eventually add code for SPNEGO decoding of NtlmChallenge blob,
         * but at least the raw NTLMSSP case works.
         */
        /*
         * No tcon so can't do
         * cifs_stats_inc(&tcon->stats.smb2_stats.smb2_com_fail[SMB2...]);
         */
        if (rc != 0)
                goto ssetup_exit;

        if (rsp == NULL) {
                rc = -EIO;
                goto ssetup_exit;
        }

        ses->session_flags = le16_to_cpu(rsp->SessionFlags);
ssetup_exit:
        free_rsp_buf(resp_buftype, rsp);

        /* if ntlmssp, and negotiate succeeded, proceed to authenticate phase */
        if ((phase == NtLmChallenge) && (rc == 0))
                goto ssetup_ntlmssp_authenticate;
        return rc;
}

int
SMB2_logoff(const unsigned int xid, struct cifs_ses *ses)
{
        struct smb2_logoff_req *req; /* response is also trivial struct */
        int rc = 0;
        struct TCP_Server_Info *server;

        cFYI(1, "disconnect session %p", ses);

        if (ses && (ses->server))
                server = ses->server;
        else
                return -EIO;

        rc = small_smb2_init(SMB2_LOGOFF, NULL, (void **) &req);
        if (rc)
                return rc;

         /* since no tcon, smb2_init can not do this, so do here */
        req->hdr.SessionId = ses->Suid;

        rc = SendReceiveNoRsp(xid, ses, (char *) &req->hdr, 0);
        /*
         * No tcon so can't do
         * cifs_stats_inc(&tcon->stats.smb2_stats.smb2_com_fail[SMB2...]);
         */
        return rc;
}

static inline void cifs_stats_fail_inc(struct cifs_tcon *tcon, uint16_t code)
{
        cifs_stats_inc(&tcon->stats.smb2_stats.smb2_com_failed[code]);
}

#define MAX_SHARENAME_LENGTH (255 /* server */ + 80 /* share */ + 1 /* NULL */)

int
SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
          struct cifs_tcon *tcon, const struct nls_table *cp)
{
        struct smb2_tree_connect_req *req;
        struct smb2_tree_connect_rsp *rsp = NULL;
        struct kvec iov[2];
        int rc = 0;
        int resp_buftype;
        int unc_path_len;
        struct TCP_Server_Info *server;
        __le16 *unc_path = NULL;

        cFYI(1, "TCON");

        if ((ses->server) && tree)
                server = ses->server;
        else
                return -EIO;

        if (tcon && tcon->bad_network_name)
                return -ENOENT;

        unc_path = kmalloc(MAX_SHARENAME_LENGTH * 2, GFP_KERNEL);
        if (unc_path == NULL)
                return -ENOMEM;

        unc_path_len = cifs_strtoUTF16(unc_path, tree, strlen(tree), cp) + 1;
        unc_path_len *= 2;
        if (unc_path_len < 2) {
                kfree(unc_path);
                return -EINVAL;
        }

        rc = small_smb2_init(SMB2_TREE_CONNECT, tcon, (void **) &req);
        if (rc) {
                kfree(unc_path);
                return rc;
        }

        if (tcon == NULL) {
                /* since no tcon, smb2_init can not do this, so do here */
                req->hdr.SessionId = ses->Suid;
                /* if (ses->server->sec_mode & SECMODE_SIGN_REQUIRED)
                        req->hdr.Flags |= SMB2_FLAGS_SIGNED; */
        }

        iov[0].iov_base = (char *)req;
        /* 4 for rfc1002 length field and 1 for pad */
        iov[0].iov_len = get_rfc1002_length(req) + 4 - 1;

        /* Testing shows that buffer offset must be at location of Buffer[0] */
        req->PathOffset = cpu_to_le16(sizeof(struct smb2_tree_connect_req)
                        - 1 /* pad */ - 4 /* do not count rfc1001 len field */);
        req->PathLength = cpu_to_le16(unc_path_len - 2);
        iov[1].iov_base = unc_path;
        iov[1].iov_len = unc_path_len;

        inc_rfc1001_len(req, unc_path_len - 1 /* pad */);

        rc = SendReceive2(xid, ses, iov, 2, &resp_buftype, 0);
        rsp = (struct smb2_tree_connect_rsp *)iov[0].iov_base;

        if (rc != 0) {
                if (tcon) {
                        cifs_stats_fail_inc(tcon, SMB2_TREE_CONNECT_HE);
                        tcon->need_reconnect = true;
                }
                goto tcon_error_exit;
        }

        if (rsp == NULL) {
                rc = -EIO;
                goto tcon_exit;
        }

        if (tcon == NULL) {
                ses->ipc_tid = rsp->hdr.TreeId;
                goto tcon_exit;
        }

        if (rsp->ShareType & SMB2_SHARE_TYPE_DISK)
                cFYI(1, "connection to disk share");
        else if (rsp->ShareType & SMB2_SHARE_TYPE_PIPE) {
                tcon->ipc = true;
                cFYI(1, "connection to pipe share");
        } else if (rsp->ShareType & SMB2_SHARE_TYPE_PRINT) {
                tcon->print = true;
                cFYI(1, "connection to printer");
        } else {
                cERROR(1, "unknown share type %d", rsp->ShareType);
                rc = -EOPNOTSUPP;
                goto tcon_error_exit;
        }

        tcon->share_flags = le32_to_cpu(rsp->ShareFlags);
        tcon->maximal_access = le32_to_cpu(rsp->MaximalAccess);
        tcon->tidStatus = CifsGood;
        tcon->need_reconnect = false;
        tcon->tid = rsp->hdr.TreeId;
        strncpy(tcon->treeName, tree, MAX_TREE_SIZE);

        if ((rsp->Capabilities & SMB2_SHARE_CAP_DFS) &&
            ((tcon->share_flags & SHI1005_FLAGS_DFS) == 0))
                cERROR(1, "DFS capability contradicts DFS flag");

tcon_exit:
        free_rsp_buf(resp_buftype, rsp);
        kfree(unc_path);
        return rc;

tcon_error_exit:
        if (rsp->hdr.Status == STATUS_BAD_NETWORK_NAME) {
                cERROR(1, "BAD_NETWORK_NAME: %s", tree);
                tcon->bad_network_name = true;
        }
        goto tcon_exit;
}

int
SMB2_tdis(const unsigned int xid, struct cifs_tcon *tcon)
{
        struct smb2_tree_disconnect_req *req; /* response is trivial */
        int rc = 0;
        struct TCP_Server_Info *server;
        struct cifs_ses *ses = tcon->ses;

        cFYI(1, "Tree Disconnect");

        if (ses && (ses->server))
                server = ses->server;
        else
                return -EIO;

        if ((tcon->need_reconnect) || (tcon->ses->need_reconnect))
                return 0;

        rc = small_smb2_init(SMB2_TREE_DISCONNECT, tcon, (void **) &req);
        if (rc)
                return rc;

        rc = SendReceiveNoRsp(xid, ses, (char *)&req->hdr, 0);
        if (rc)
                cifs_stats_fail_inc(tcon, SMB2_TREE_DISCONNECT_HE);

        return rc;
}

int
SMB2_open(const unsigned int xid, struct cifs_tcon *tcon, __le16 *path,
          u64 *persistent_fid, u64 *volatile_fid, __u32 desired_access,
          __u32 create_disposition, __u32 file_attributes, __u32 create_options)
{
        struct smb2_create_req *req;
        struct smb2_create_rsp *rsp;
        struct TCP_Server_Info *server;
        struct cifs_ses *ses = tcon->ses;
        struct kvec iov[2];
        int resp_buftype;
        int uni_path_len;
        int rc = 0;
        int num_iovecs = 2;

        cFYI(1, "create/open");

        if (ses && (ses->server))
                server = ses->server;
        else
                return -EIO;

        rc = small_smb2_init(SMB2_CREATE, tcon, (void **) &req);
        if (rc)
                return rc;

        if (enable_oplocks)
                req->RequestedOplockLevel = SMB2_OPLOCK_LEVEL_BATCH;
        else
                req->RequestedOplockLevel = SMB2_OPLOCK_LEVEL_NONE;
        req->ImpersonationLevel = IL_IMPERSONATION;
        req->DesiredAccess = cpu_to_le32(desired_access);
        /* File attributes ignored on open (used in create though) */
        req->FileAttributes = cpu_to_le32(file_attributes);
        req->ShareAccess = FILE_SHARE_ALL_LE;
        req->CreateDisposition = cpu_to_le32(create_disposition);
        req->CreateOptions = cpu_to_le32(create_options);
        uni_path_len = (2 * UniStrnlen((wchar_t *)path, PATH_MAX)) + 2;
        req->NameOffset = cpu_to_le16(sizeof(struct smb2_create_req)
                        - 1 /* pad */ - 4 /* do not count rfc1001 len field */);

        iov[0].iov_base = (char *)req;
        /* 4 for rfc1002 length field */
        iov[0].iov_len = get_rfc1002_length(req) + 4;

        /* MUST set path len (NameLength) to 0 opening root of share */
        if (uni_path_len >= 4) {
                req->NameLength = cpu_to_le16(uni_path_len - 2);
                /* -1 since last byte is buf[0] which is sent below (path) */
                iov[0].iov_len--;
                iov[1].iov_len = uni_path_len;
                iov[1].iov_base = path;
                /*
                 * -1 since last byte is buf[0] which was counted in
                 * smb2_buf_len.
                 */
                inc_rfc1001_len(req, uni_path_len - 1);
        } else {
                num_iovecs = 1;
                req->NameLength = 0;
        }

        rc = SendReceive2(xid, ses, iov, num_iovecs, &resp_buftype, 0);
        rsp = (struct smb2_create_rsp *)iov[0].iov_base;

        if (rc != 0) {
                cifs_stats_fail_inc(tcon, SMB2_CREATE_HE);
                goto creat_exit;
        }

        if (rsp == NULL) {
                rc = -EIO;
                goto creat_exit;
        }
        *persistent_fid = rsp->PersistentFileId;
        *volatile_fid = rsp->VolatileFileId;
creat_exit:
        free_rsp_buf(resp_buftype, rsp);
        return rc;
}

int
SMB2_close(const unsigned int xid, struct cifs_tcon *tcon,
           u64 persistent_fid, u64 volatile_fid)
{
        struct smb2_close_req *req;
        struct smb2_close_rsp *rsp;
        struct TCP_Server_Info *server;
        struct cifs_ses *ses = tcon->ses;
        struct kvec iov[1];
        int resp_buftype;
        int rc = 0;

        cFYI(1, "Close");

        if (ses && (ses->server))
                server = ses->server;
        else
                return -EIO;

        rc = small_smb2_init(SMB2_CLOSE, tcon, (void **) &req);
        if (rc)
                return rc;

        req->PersistentFileId = persistent_fid;
        req->VolatileFileId = volatile_fid;

        iov[0].iov_base = (char *)req;
        /* 4 for rfc1002 length field */
        iov[0].iov_len = get_rfc1002_length(req) + 4;

        rc = SendReceive2(xid, ses, iov, 1, &resp_buftype, 0);
        rsp = (struct smb2_close_rsp *)iov[0].iov_base;

        if (rc != 0) {
                if (tcon)
                        cifs_stats_fail_inc(tcon, SMB2_CLOSE_HE);
                goto close_exit;
        }

        if (rsp == NULL) {
                rc = -EIO;
                goto close_exit;
        }

        /* BB FIXME - decode close response, update inode for caching */

close_exit:
        free_rsp_buf(resp_buftype, rsp);
        return rc;
}

static int
validate_buf(unsigned int offset, unsigned int buffer_length,
             struct smb2_hdr *hdr, unsigned int min_buf_size)

{
        unsigned int smb_len = be32_to_cpu(hdr->smb2_buf_length);
        char *end_of_smb = smb_len + 4 /* RFC1001 length field */ + (char *)hdr;
        char *begin_of_buf = 4 /* RFC1001 len field */ + offset + (char *)hdr;
        char *end_of_buf = begin_of_buf + buffer_length;


        if (buffer_length < min_buf_size) {
                cERROR(1, "buffer length %d smaller than minimum size %d",
                           buffer_length, min_buf_size);
                return -EINVAL;
        }

        /* check if beyond RFC1001 maximum length */
        if ((smb_len > 0x7FFFFF) || (buffer_length > 0x7FFFFF)) {
                cERROR(1, "buffer length %d or smb length %d too large",
                           buffer_length, smb_len);
                return -EINVAL;
        }

        if ((begin_of_buf > end_of_smb) || (end_of_buf > end_of_smb)) {
                cERROR(1, "illegal server response, bad offset to data");
                return -EINVAL;
        }

        return 0;
}

/*
 * If SMB buffer fields are valid, copy into temporary buffer to hold result.
 * Caller must free buffer.
 */

static int
validate_and_copy_buf(unsigned int offset, unsigned int buffer_length,
                      struct smb2_hdr *hdr, unsigned int minbufsize,
                      char *data)

{
        char *begin_of_buf = 4 /* RFC1001 len field */ + offset + (char *)hdr;
        int rc;

        if (!data)
                return -EINVAL;

        rc = validate_buf(offset, buffer_length, hdr, minbufsize);
        if (rc)
                return rc;

        memcpy(data, begin_of_buf, buffer_length);

        return 0;
}

int
SMB2_query_info(const unsigned int xid, struct cifs_tcon *tcon,
                u64 persistent_fid, u64 volatile_fid,
                struct smb2_file_all_info *data)
{
        struct smb2_query_info_req *req;
        struct smb2_query_info_rsp *rsp = NULL;
        struct kvec iov[2];
        int rc = 0;
        int resp_buftype;
        struct TCP_Server_Info *server;
        struct cifs_ses *ses = tcon->ses;

        cFYI(1, "Query Info");

        if (ses && (ses->server))
                server = ses->server;
        else
                return -EIO;

        rc = small_smb2_init(SMB2_QUERY_INFO, tcon, (void **) &req);
        if (rc)
                return rc;

        req->InfoType = SMB2_O_INFO_FILE;
        req->FileInfoClass = FILE_ALL_INFORMATION;
        req->PersistentFileId = persistent_fid;
        req->VolatileFileId = volatile_fid;
        /* 4 for rfc1002 length field and 1 for Buffer */
        req->InputBufferOffset =
                cpu_to_le16(sizeof(struct smb2_query_info_req) - 1 - 4);
        req->OutputBufferLength =
                cpu_to_le32(sizeof(struct smb2_file_all_info) + MAX_NAME * 2);

        iov[0].iov_base = (char *)req;
        /* 4 for rfc1002 length field */
        iov[0].iov_len = get_rfc1002_length(req) + 4;

        rc = SendReceive2(xid, ses, iov, 1, &resp_buftype, 0);
        if (rc) {
                cifs_stats_fail_inc(tcon, SMB2_QUERY_INFO_HE);
                goto qinf_exit;
        }

        rsp = (struct smb2_query_info_rsp *)iov[0].iov_base;

        rc = validate_and_copy_buf(le16_to_cpu(rsp->OutputBufferOffset),
                                   le32_to_cpu(rsp->OutputBufferLength),
                                   &rsp->hdr, sizeof(struct smb2_file_all_info),
                                   (char *)data);

qinf_exit:
        free_rsp_buf(resp_buftype, rsp);
        return rc;
}

/*
 * This is a no-op for now. We're not really interested in the reply, but
 * rather in the fact that the server sent one and that server->lstrp
 * gets updated.
 *
 * FIXME: maybe we should consider checking that the reply matches request?
 */
static void
smb2_echo_callback(struct mid_q_entry *mid)
{
        struct TCP_Server_Info *server = mid->callback_data;
        struct smb2_echo_rsp *smb2 = (struct smb2_echo_rsp *)mid->resp_buf;
        unsigned int credits_received = 1;

        if (mid->mid_state == MID_RESPONSE_RECEIVED)
                credits_received = le16_to_cpu(smb2->hdr.CreditRequest);

        DeleteMidQEntry(mid);
        add_credits(server, credits_received, CIFS_ECHO_OP);
}

int
SMB2_echo(struct TCP_Server_Info *server)
{
        struct smb2_echo_req *req;
        int rc = 0;
        struct kvec iov;

        cFYI(1, "In echo request");

        rc = small_smb2_init(SMB2_ECHO, NULL, (void **)&req);
        if (rc)
                return rc;

        req->hdr.CreditRequest = cpu_to_le16(1);

        iov.iov_base = (char *)req;
        /* 4 for rfc1002 length field */
        iov.iov_len = get_rfc1002_length(req) + 4;

        rc = cifs_call_async(server, &iov, 1, NULL, smb2_echo_callback, server,
                             CIFS_ECHO_OP);
        if (rc)
                cFYI(1, "Echo request failed: %d", rc);

        cifs_small_buf_release(req);
        return rc;
}