On Wed, 16 Oct 2013 09:09:50 -0600
Tim Gardner <timg@xxxxxxx> 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: Steve French <sfrench@xxxxxxxxx>
> Signed-off-by: Tim Gardner <timg@xxxxxxx>
> ---
>
> I'm looking at some of this code in excrutiating detail because I'm having trouble
> with a backport of CIFS from 3.9.7 on an embedded 2.6.31 powerpc. Its failing the RawNTLMSSP
> authentication and is almost certainly an endian issue. x86 on the same code base works
> quite well. Am I making a rash assumption that CIFS in 3.9 stable worked on big endian ?
>
> fs/cifs/cifsglob.h | 25 ++++++++++++++++++++++++-
> fs/cifs/misc.c | 9 +++++----
> fs/cifs/smb1ops.c | 4 ++--
> fs/cifs/smb2transport.c | 2 +-
> fs/cifs/transport.c | 2 +-
> 5 files changed, 33 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..c851d41 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",
> + le16_to_cpu(smb->Mid));
> return 1;
> }
>
> @@ -358,11 +359,11 @@ 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, le16_to_cpu(smb->Mid));
>
> if (4 + rfclen < clc_len) {
> cifs_dbg(VFS, "RFC1001 size %u smaller than SMB for mid=%u\n",
> - rfclen, smb->Mid);
> + rfclen, le16_to_cpu(smb->Mid));
> return -EIO;
> } else if (rfclen > clc_len + 512) {
> /*
> @@ -375,7 +376,7 @@ 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, le16_to_cpu(smb->Mid));
> return -EIO;
> }
> }
It would be more efficient to byte-swap smb->Mid only once and store
that in a u16 here and then print that out instead of doing it multiple
times.
> diff --git a/fs/cifs/smb1ops.c b/fs/cifs/smb1ops.c
> index 8233b17..5598af9 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);
> + le16_to_cpu(in_buf->Mid), 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);
Otherwise, this seems like a good thing to do...
--
Jeff Layton <jlayton@xxxxxxxxxx>
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