[PATCH linux-next V2] cifs: Make big endian multiplex ID sequences monotonic on the wire
Steve French
smfrench at gmail.com
Mon Oct 28 08:38:24 MDT 2013
merged into cifs-2.6.git for-next
On Wed, Oct 16, 2013 at 3:03 PM, Jeff Layton <jlayton at redhat.com> wrote:
> On Wed, 16 Oct 2013 10:32:42 -0600
> Tim Gardner <timg at tpi.com> wrote:
>
>> The multiplex identifier (MID) in the SMB header is only
>> ever used by the client, in conjunction with PID, to match responses
>> from the server. As such, the endianess of the MID is not important.
>> However, When tracing packet sequences on the wire, protocol analyzers
>> such as wireshark display MID as little endian. It is much more informative
>> for the on-the-wire MID sequences to match debug information emitted by the
>> CIFS driver. Therefore, one should write and read MID in the SMB header
>> assuming it is always little endian.
>>
>> Observed from wireshark during the protocol negotiation
>> and session setup:
>>
>> Multiplex ID: 256
>> Multiplex ID: 256
>> Multiplex ID: 512
>> Multiplex ID: 512
>> Multiplex ID: 768
>> Multiplex ID: 768
>>
>> After this patch on-the-wire MID values begin at 1 and increase monotonically.
>>
>> Introduce get_next_mid64() for the internal consumers that use the full 64 bit
>> multiplex identifier.
>>
>> Introduce the helpers get_mid() and compare_mid() to make the endian
>> translation clear.
>>
>> Cc: Jeff Layton <jlayton at redhat.com>
>> Cc: Steve French <sfrench at samba.org>
>> Signed-off-by: Tim Gardner <timg at tpi.com>
>> ---
>>
>> V2 - get an endian appropriate copy of 'mid' for debug output in checkSMB().
>> Actually use the new helper get_mid() wherever smb->Mid is referenced.
>>
>> fs/cifs/cifsglob.h | 25 ++++++++++++++++++++++++-
>> fs/cifs/misc.c | 10 ++++++----
>> fs/cifs/smb1ops.c | 4 ++--
>> fs/cifs/smb2transport.c | 2 +-
>> fs/cifs/transport.c | 2 +-
>> 5 files changed, 34 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
>> index 52b6f6c..535e324 100644
>> --- a/fs/cifs/cifsglob.h
>> +++ b/fs/cifs/cifsglob.h
>> @@ -620,11 +620,34 @@ set_credits(struct TCP_Server_Info *server, const int val)
>> }
>>
>> static inline __u64
>> -get_next_mid(struct TCP_Server_Info *server)
>> +get_next_mid64(struct TCP_Server_Info *server)
>> {
>> return server->ops->get_next_mid(server);
>> }
>>
>> +static inline __u16
>> +get_next_mid(struct TCP_Server_Info *server)
>> +{
>> + __u16 mid = get_next_mid64(server);
>> + /*
>> + * The value in the SMB header should be little endian for easy
>> + * on-the-wire decoding.
>> + */
>> + return cpu_to_le16(mid);
>> +}
>> +
>> +static inline __u16
>> +get_mid(const struct smb_hdr *smb)
>> +{
>> + return le16_to_cpu(smb->Mid);
>> +}
>> +
>> +static inline bool
>> +compare_mid(__u16 mid, const struct smb_hdr *smb)
>> +{
>> + return mid == le16_to_cpu(smb->Mid);
>> +}
>> +
>> /*
>> * When the server supports very large reads and writes via POSIX extensions,
>> * we can allow up to 2^24-1, minus the size of a READ/WRITE_AND_X header, not
>> diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
>> index 298e31e..2f9f379 100644
>> --- a/fs/cifs/misc.c
>> +++ b/fs/cifs/misc.c
>> @@ -295,7 +295,8 @@ check_smb_hdr(struct smb_hdr *smb)
>> if (smb->Command == SMB_COM_LOCKING_ANDX)
>> return 0;
>>
>> - cifs_dbg(VFS, "Server sent request, not response. mid=%u\n", smb->Mid);
>> + cifs_dbg(VFS, "Server sent request, not response. mid=%u\n",
>> + get_mid(smb));
>> return 1;
>> }
>>
>> @@ -351,6 +352,7 @@ checkSMB(char *buf, unsigned int total_read)
>> }
>>
>> if (4 + rfclen != clc_len) {
>> + __u16 mid = get_mid(smb);
>> /* check if bcc wrapped around for large read responses */
>> if ((rfclen > 64 * 1024) && (rfclen > clc_len)) {
>> /* check if lengths match mod 64K */
>> @@ -358,11 +360,11 @@ checkSMB(char *buf, unsigned int total_read)
>> return 0; /* bcc wrapped */
>> }
>> cifs_dbg(FYI, "Calculated size %u vs length %u mismatch for mid=%u\n",
>> - clc_len, 4 + rfclen, smb->Mid);
>> + clc_len, 4 + rfclen, mid);
>>
>> if (4 + rfclen < clc_len) {
>> cifs_dbg(VFS, "RFC1001 size %u smaller than SMB for mid=%u\n",
>> - rfclen, smb->Mid);
>> + rfclen, mid);
>> return -EIO;
>> } else if (rfclen > clc_len + 512) {
>> /*
>> @@ -375,7 +377,7 @@ checkSMB(char *buf, unsigned int total_read)
>> * data to 512 bytes.
>> */
>> cifs_dbg(VFS, "RFC1001 size %u more than 512 bytes larger than SMB for mid=%u\n",
>> - rfclen, smb->Mid);
>> + rfclen, mid);
>> return -EIO;
>> }
>> }
>> diff --git a/fs/cifs/smb1ops.c b/fs/cifs/smb1ops.c
>> index 8233b17..09ef8f3 100644
>> --- a/fs/cifs/smb1ops.c
>> +++ b/fs/cifs/smb1ops.c
>> @@ -67,7 +67,7 @@ send_nt_cancel(struct TCP_Server_Info *server, void *buf,
>> mutex_unlock(&server->srv_mutex);
>>
>> cifs_dbg(FYI, "issued NT_CANCEL for mid %u, rc = %d\n",
>> - in_buf->Mid, rc);
>> + get_mid(in_buf), rc);
>>
>> return rc;
>> }
>> @@ -101,7 +101,7 @@ cifs_find_mid(struct TCP_Server_Info *server, char *buffer)
>>
>> spin_lock(&GlobalMid_Lock);
>> list_for_each_entry(mid, &server->pending_mid_q, qhead) {
>> - if (mid->mid == buf->Mid &&
>> + if (compare_mid(mid->mid, buf) &&
>> mid->mid_state == MID_REQUEST_SUBMITTED &&
>> le16_to_cpu(mid->command) == buf->Command) {
>> spin_unlock(&GlobalMid_Lock);
>> diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
>> index 340abca..c523617 100644
>> --- a/fs/cifs/smb2transport.c
>> +++ b/fs/cifs/smb2transport.c
>> @@ -466,7 +466,7 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
>> static inline void
>> smb2_seq_num_into_buf(struct TCP_Server_Info *server, struct smb2_hdr *hdr)
>> {
>> - hdr->MessageId = get_next_mid(server);
>> + hdr->MessageId = get_next_mid64(server);
>> }
>>
>> static struct mid_q_entry *
>> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
>> index 6fdcb1b..057b2c0 100644
>> --- a/fs/cifs/transport.c
>> +++ b/fs/cifs/transport.c
>> @@ -58,7 +58,7 @@ AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server)
>> return temp;
>> else {
>> memset(temp, 0, sizeof(struct mid_q_entry));
>> - temp->mid = smb_buffer->Mid; /* always LE */
>> + temp->mid = get_mid(smb_buffer);
>> temp->pid = current->pid;
>> temp->command = cpu_to_le16(smb_buffer->Command);
>> cifs_dbg(FYI, "For smb_command %d\n", smb_buffer->Command);
>
> Looks good...
>
> Reviewed-by: Jeff Layton <jlayton at redhat.com>
--
Thanks,
Steve
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