On Thu, Jan 20, 2022 at 02:18:57AM -0800, daniel.starke@xxxxxxxxxxx wrote: > n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010. > See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516 > The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to > the newer 27.010 here. Chapter 5.2.7.3 states that DC1 (XON) and DC3 (XOFF) > are the control characters defined in ISO/IEC 646. These shall be quoted if > seen in the data stream to avoid interpretation as flow control characters. > > ISO/IEC 646 refers to the set of ISO standards described as the ISO > 7-bit coded character set for information interchange. Its final version > is also known as ITU T.50. > See https://www.itu.int/rec/T-REC-T.50-199209-I/en > > To abide the standard it is needed to quote DC1 and DC3 correctly if these > are seen as data bytes and not as control characters. The current > implementation already tries to enforce this but fails to catch all > defined cases. 3GPP 27.010 chapter 5.2.7.3 clearly states that the most > significant bit shall be ignored for DC1 and DC3 handling. The current > implementation handles only the case with the most significant bit set 0. > Cases in which DC1 and DC3 have the most significant bit set 1 are left > unhandled. > > This patch fixes this by masking the data bytes with ISO_IEC_646_MASK (only > the 7 least significant bits set 1) before comparing them with XON > (a.k.a. DC1) and XOFF (a.k.a. DC3) when testing which byte values need > quotation via byte stuffing. > > Fixes: e1eaea46bb40 (tty: n_gsm line discipline, 2010-03-26) Nit, no need for a date here, our tools get mad about stuff like this. Look at the proper format for "Fixes:" line in the documentation. thanks, greg k-h
