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authorJeremy Allison <jra@samba.org>2013-03-15 11:57:48 -0700
committerJeremy Allison <jra@samba.org>2013-03-20 09:32:26 -0700
commitfd88520497b4043e9d81656f7cb56a7b25245c2a (patch)
treefab3fa19a01e59b91936839eb52e752a81a30d81 /source3
parent21707defe06e1db18a6645b0b56db4178e3df5f6 (diff)
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s3:smbd: Add functions calc_max_read_pdu()/calc_read_size() to work out the length we should return.
LARGE_READX test shows it's always safe to return a short read. Windows does so. Do the calculations to return what will fit in a read depending on what the client negotiated. Signed-off-by: Jeremy Allison <jra@samba.org> Signed-off-by: Stefan Metzmacher <metze@samba.org> Reviewed-by: Stefan Metzmacher <metze@samba.org>
Diffstat (limited to 'source3')
-rw-r--r--source3/smbd/reply.c111
1 files changed, 86 insertions, 25 deletions
diff --git a/source3/smbd/reply.c b/source3/smbd/reply.c
index edcfb77b3e..8b500c5387 100644
--- a/source3/smbd/reply.c
+++ b/source3/smbd/reply.c
@@ -3848,6 +3848,84 @@ nosendfile_read:
}
/****************************************************************************
+ Work out how much space we have for a read return.
+****************************************************************************/
+
+static size_t calc_max_read_pdu(const struct smb_request *req)
+{
+ if (req->sconn->conn->protocol < PROTOCOL_NT1) {
+ return req->sconn->smb1.sessions.max_send;
+ }
+
+ if (!lp_large_readwrite()) {
+ return req->sconn->smb1.sessions.max_send;
+ }
+
+ if (req_is_in_chain(req)) {
+ return req->sconn->smb1.sessions.max_send;
+ }
+
+ if (req->encrypted) {
+ /*
+ * Don't take encrypted traffic up to the
+ * limit. There are padding considerations
+ * that make that tricky.
+ */
+ return req->sconn->smb1.sessions.max_send;
+ }
+
+ if (srv_is_signing_active(req->sconn)) {
+ return 0x1FFFF;
+ }
+
+ if (!lp_unix_extensions()) {
+ return 0x1FFFF;
+ }
+
+ /*
+ * We can do ultra-large POSIX reads.
+ */
+ return 0xFFFFFF;
+}
+
+/****************************************************************************
+ Calculate how big a read can be. Copes with all clients. It's always
+ safe to return a short read - Windows does this.
+****************************************************************************/
+
+static size_t calc_read_size(const struct smb_request *req,
+ size_t upper_size,
+ size_t lower_size)
+{
+ size_t max_pdu = calc_max_read_pdu(req);
+ size_t total_size = 0;
+ size_t hdr_len = MIN_SMB_SIZE + VWV(12);
+ size_t max_len = max_pdu - hdr_len;
+
+ /*
+ * Windows explicitly ignores upper size of 0xFFFF.
+ * See [MS-SMB].pdf <26> Section 2.2.4.2.1:
+ * We must do the same as these will never fit even in
+ * an extended size NetBIOS packet.
+ */
+ if (upper_size == 0xFFFF) {
+ upper_size = 0;
+ }
+
+ if (req->sconn->conn->protocol < PROTOCOL_NT1) {
+ upper_size = 0;
+ }
+
+ total_size = ((upper_size<<16) | lower_size);
+
+ /*
+ * LARGE_READX test shows it's always safe to return
+ * a short read. Windows does so.
+ */
+ return MIN(total_size, max_len);
+}
+
+/****************************************************************************
Reply to a read and X.
****************************************************************************/
@@ -3893,31 +3971,14 @@ void reply_read_and_X(struct smb_request *req)
}
upper_size = SVAL(req->vwv+7, 0);
- if (upper_size != 0) {
- smb_maxcnt |= (upper_size<<16);
- if (upper_size > 1) {
- /* Can't do this on a chained packet. */
- if ((CVAL(req->vwv+0, 0) != 0xFF)) {
- reply_nterror(req, NT_STATUS_NOT_SUPPORTED);
- END_PROFILE(SMBreadX);
- return;
- }
- /* We currently don't do this on signed or sealed data. */
- if (srv_is_signing_active(req->sconn) ||
- is_encrypted_packet(req->sconn, req->inbuf)) {
- reply_nterror(req, NT_STATUS_NOT_SUPPORTED);
- END_PROFILE(SMBreadX);
- return;
- }
- /* Is there room in the reply for this data ? */
- if (smb_maxcnt > (0xFFFFFF - (smb_size -4 + 12*2))) {
- reply_nterror(req,
- NT_STATUS_INVALID_PARAMETER);
- END_PROFILE(SMBreadX);
- return;
- }
- big_readX = True;
- }
+ smb_maxcnt = calc_read_size(req, upper_size, smb_maxcnt);
+ if (smb_maxcnt > (0x1FFFF - (MIN_SMB_SIZE + VWV(12)))) {
+ /*
+ * This is a heuristic to avoid keeping large
+ * outgoing buffers around over long-lived aio
+ * requests.
+ */
+ big_readX = True;
}
if (req->wct == 12) {