On Wed, 26 Oct 2016 21:49:35 +0300 Isaac Boukris <ibouk...@gmail.com> wrote:
> Hi Stephen, thanks for looking into this. > > On Wed, Oct 26, 2016 at 8:15 PM, Stephen Hemminger > <step...@networkplumber.org> wrote: > > On Tue, 18 Oct 2016 21:46:48 +0300 > > Isaac Boukris <ibouk...@gmail.com> wrote: > > > >> Hi again, > >> > >> On Sun, Oct 16, 2016 at 11:43 PM, Isaac Boukris <ibouk...@gmail.com> > >> wrote: > >> > Hello, > >> > > >> > The unix(7) man page says that null have no special meaning in > >> > abstract unix domain socket address (the length is specified > >> > therefore). > >> > > >> > However, when such name (embedding null) is used, ss (and netstat) > >> > will only show up to the first null occurrence (second technically, if > >> > we count the null prefix). > >> > e.g. the name "\0/tmp/fo\0.sock" is displayed as: "@/tmp/fo" (whilst > >> > strace tool shows it as: sun_path=@"/tmp/fo\0.sock"). > >> > > >> > Would it be more useful if it printed the whole name and escaped the > >> > null? > >> > If so, would '\0' be ok for escaping the null? > >> > >> > >> Meanwhile, I've got it to escape the null character with with '\0' as > >> suggested. > >> Can anyone take a look and advise if I'm on the right track? Thanks! > > > > I did a little investigation and current ss behavior matches the output > > of other commands (netstat and lsof). Therefore I really can't see the > > motivation > > to fix this. > > The motivation behind the fix is because the usage of abstract unix > domain socket is somewhat tricky. > I've seen it being used incorrectly where for example the addrlen was > specified as 'sizeof(struct sockaddr_un)' which is ok for regular unix > sockets because their names are null-terminated, but with abstract > sockets it causes extra null padding which leads to interoperability > problems. > On another occasion, addrlen was incremented to account for an > additional null-termination byte. > > I was thinking therefore, it could help if the diagnostic tools would > show all the significant bytes of the name in order to make it clear > and easy to distinguish. > > On the other hand, I think I've complicated it a little bit with the > '\0' escaping. > Perhaps it would suffice to substitute each null character with an '@' > sign, the same way we do for the null prefix. > > As regarding netstat, I have in fact made a patch for it, but then I > realized it perhaps isn't its fault as it prints what it reads from > '/proc/net/unix' which prints the null prefix as '@' but leaves > subsequent nulls as is (literally, can be seen with 'cat -A'). > So I'm trying to see if '/proc/net/unix' can be fixed to translate all > null occurrences to '@' sign (not only the prefix). > This should fix netstat and also (I think) the alternative 'proc' base > implementation in ss (unix_use_proc). > > What do you think? Just translating all null characters to @ seems the most consistent and logical. Also translating other all non-printing characters to something (maybe '?') might be wise. It would be nice if all utilities output the same thing.
