On RT-AC87U, 378.50.
When I mount an SMB share using Windows 10 Technical Preview, I can successfully get to the files on the AC87U. But, syslog shows the following:
Feb 8 09:11:06 smbd[9183]: [2015/02/08 09:11:06.591939, 0] ../libcli/auth/ntlm_check.c:54(smb_pwd_check_ntlmv1)
Feb 8 09:11:06 smbd[9183]: smb_pwd_check_ntlmv1: incorrect password length (74)
Feb 8 09:11:06 smbd[9183]: [2015/02/08 09:11:06.593464, 0] ../libcli/auth/ntlm_check.c:54(smb_pwd_check_ntlmv1)
Feb 8 09:11:06 smbd[9183]: smb_pwd_check_ntlmv1: incorrect password length (74)
Feb 8 09:12:26 smbd[9183]: [2015/02/08 09:12:26.068810, 0] ../libcli/auth/ntlm_check.c:54(smb_pwd_check_ntlmv1)
Feb 8 09:12:26 smbd[9183]: smb_pwd_check_ntlmv1: incorrect password length (74)
Feb 8 09:12:26 smbd[9183]: [2015/02/08 09:12:26.070316, 0] ../libcli/auth/ntlm_check.c:54(smb_pwd_check_ntlmv1)
Feb 8 09:12:26 smbd[9183]: smb_pwd_check_ntlmv1: incorrect password length (74)
Feb 8 09:12:59 smbd[9183]: [2015/02/08 09:12:59.554153, 0] ../libcli/auth/ntlm_check.c:54(smb_pwd_check_ntlmv1)
Feb 8 09:12:59 smbd[9183]: smb_pwd_check_ntlmv1: incorrect password length (74)
Feb 8 09:12:59 smbd[9183]: [2015/02/08 09:12:59.556055, 0] ../libcli/auth/ntlm_check.c:54(smb_pwd_check_ntlmv1)
Feb 8 09:12:59 smbd[9183]: smb_pwd_check_ntlmv1: incorrect password length (74)
Feb 8 09:13:40 smbd[9183]: [2015/02/08 09:13:40.661159, 0] ../libcli/auth/ntlm_check.c:54(smb_pwd_check_ntlmv1)
Feb 8 09:13:40 smbd[9183]: smb_pwd_check_ntlmv1: incorrect password length (74)
Feb 8 09:13:40 smbd[9183]: [2015/02/08 09:13:40.663094, 0] ../libcli/auth/ntlm_check.c:54(smb_pwd_check_ntlmv1)
Feb 8 09:13:40 smbd[9183]: smb_pwd_check_ntlmv1: incorrect password length (74)
You can see from the timestamps, the first 4 were from first opening the share. The next 4 are from opening a directory on the share. The last 4 are from opening a file from another directory.
I have "Allow guest login" on.
Maybe a Windows 10 thing? I don't recall see this with the earlier beta's. I did a grep on /tmp/syslog.log-1 and no sign of smb_pwd errors.