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?
