Problem with --link-dest when syncing AIX to Linux

[Markus Marquardt]

Hello,

i'm using rsync 2.6.0 for daily-syncing some remote AIX 5.2 machine to a 
local linux (RH 7.3) with using the --link-dest option for saving space 
on incremental backups.

Even if there are no changes on the AIX machine, all files are newly 
transferred on every new sync.

My test scenario (actisi=remote aix machine, actisa=local linux machine):

=====> Initial rsync

[mma at actisa rsync-2.6.0]$ ./rsync -av actisi:remotetest/ test1/
receiving file list ... done
./
file1
file2

wrote 56 bytes  read 203 bytes  103.60 bytes/sec
total size is 14  speedup is 0.05

=====> Check if anything left...

[mma at actisa rsync-2.6.0]$ ./rsync -av actisi:remotetest/ test1/
receiving file list ... done

wrote 16 bytes  read 101 bytes  46.80 bytes/sec
total size is 14  speedup is 0.12

=====> All fine, now using --link-dest for incremental rsync

[mma at actisa rsync-2.6.0]$ ./rsync -av --link-dest=../test1 
actisi:remotetest/ test2/
receiving file list ... done
./
file1
file2

wrote 68 bytes  read 189 bytes  102.80 bytes/sec
total size is 14  speedup is 0.05

=====> Oooops. Why were file1 and file2 transferred?

I did some debugging and found out that the problem seems to be in the 
function skip_file() in generator.c:

if (link_dest) {
     extern int preserve_perms;
     extern int preserve_uid;
     extern int preserve_gid;

     if(preserve_perms
         && (st->st_mode & ~_S_IFMT) !=  (file->mode & ~_S_IFMT))
         return 0;

This is always true when rsyncing AIX -> linux, look at this gdb output:

(gdb) print /o st->st_mode
$13 = 0100644
(gdb) print /o file->mode
$14 = 0500644

Nasty AIX always adds 0400000 to the file mode which then breaks this 
condition. I've not found anything about this value in the AIX includes 
(mode.h). Is there any way to mask this bit out for AIX to make rsync 
better working?

Regards,

Markus