cifs: negotiate chained SMB2 compression capabilities

Advertise LZ77 and Pattern_V1 with chained transform support in the
SMB 3.1.1 compression negotiate context. Validate the server's returned
algorithm list and flags, then retain the negotiated capabilities for a
future compressed transform receive implementation.

This patch only negotiates capabilities. It does not request compressed
READ responses or add a compressed transform receive path.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 82e0adc1dabd05c0062948bf7af54dbf34b91b11..a3ac4aa4bbc6f74c484af25a2d31ee195fc34b5b 100644 (file)
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -789,6 +789,8 @@ struct TCP_Server_Info {
        struct {
                bool requested; /* "compress" mount option set*/
                bool enabled; /* actually negotiated with server */
+               bool chained; /* chained transforms were negotiated */
+               bool pattern; /* Pattern_V1 chained payloads were negotiated */
                __le16 alg; /* preferred alg negotiated with server */
        } compression;
        __u16   signing_algorithm;

diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index fbeb2156ddb6b08f5cf4bc9720f7452a805700c9..a79d8e6091d0b145befc242de6142ed45ca4f781 100644 (file)
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -636,10 +636,16 @@ build_compression_ctxt(struct smb2_compression_capabilities_context *pneg_ctxt)
        pneg_ctxt->DataLength =
                cpu_to_le16(sizeof(struct smb2_compression_capabilities_context)
                          - sizeof(struct smb2_neg_context));
-       pneg_ctxt->CompressionAlgorithmCount = cpu_to_le16(3);
+       /*
+        * Pattern_V1 is useful only as part of a chained transform. LZ77 remains
+        * the preferred general-purpose algorithm selected by this client.
+        */
+       pneg_ctxt->CompressionAlgorithmCount = cpu_to_le16(4);
+       pneg_ctxt->Flags = SMB2_COMPRESSION_CAPABILITIES_FLAG_CHAINED;
        pneg_ctxt->CompressionAlgorithms[0] = SMB3_COMPRESS_LZ77;
        pneg_ctxt->CompressionAlgorithms[1] = SMB3_COMPRESS_LZ77_HUFF;
        pneg_ctxt->CompressionAlgorithms[2] = SMB3_COMPRESS_LZNT1;
+       pneg_ctxt->CompressionAlgorithms[3] = SMB3_COMPRESS_PATTERN;
 }
 
 static unsigned int
@@ -827,9 +833,12 @@ static void decode_compress_ctx(struct TCP_Server_Info *server,
                         struct smb2_compression_capabilities_context *ctxt)
 {
        unsigned int len = le16_to_cpu(ctxt->DataLength);
-       __le16 alg;
+       unsigned int count, i;
 
        server->compression.enabled = false;
+       server->compression.chained = false;
+       server->compression.pattern = false;
+       server->compression.alg = SMB3_COMPRESS_NONE;
 
        /*
         * Caller checked that DataLength remains within SMB boundary. We still
@@ -841,20 +850,37 @@ static void decode_compress_ctx(struct TCP_Server_Info *server,
                return;
        }
 
-       if (le16_to_cpu(ctxt->CompressionAlgorithmCount) != 1) {
+       count = le16_to_cpu(ctxt->CompressionAlgorithmCount);
+       if (!count || count > ARRAY_SIZE(ctxt->CompressionAlgorithms) ||
+           len < 8 + count * sizeof(__le16)) {
                pr_warn_once("invalid SMB3 compress algorithm count\n");
                return;
        }
 
-       alg = ctxt->CompressionAlgorithms[0];
-
-       /* 'NONE' (0) compressor type is never negotiated */
-       if (alg == 0 || le16_to_cpu(alg) > 3) {
-               pr_warn_once("invalid compression algorithm '%u'\n", alg);
+       if (ctxt->Flags != SMB2_COMPRESSION_CAPABILITIES_FLAG_NONE &&
+           ctxt->Flags != SMB2_COMPRESSION_CAPABILITIES_FLAG_CHAINED) {
+               pr_warn_once("invalid SMB3 compression flags\n");
                return;
        }
 
-       server->compression.alg = alg;
+       for (i = 0; i < count; i++) {
+               /* Record the intersection supported by the shared SMB codec. */
+               if (ctxt->CompressionAlgorithms[i] == SMB3_COMPRESS_LZ77)
+                       server->compression.alg = SMB3_COMPRESS_LZ77;
+               else if (ctxt->CompressionAlgorithms[i] == SMB3_COMPRESS_PATTERN)
+                       server->compression.pattern = true;
+       }
+       if (server->compression.alg != SMB3_COMPRESS_LZ77)
+               return;
+
+       /*
+        * Pattern_V1 cannot appear in an unchained transform even if a broken
+        * peer lists it in the algorithm array.
+        */
+       server->compression.chained =
+               ctxt->Flags == SMB2_COMPRESSION_CAPABILITIES_FLAG_CHAINED;
+       if (!server->compression.chained)
+               server->compression.pattern = false;
        server->compression.enabled = true;
 }