[CRIU] [PATCH] net/ip: print fd link of the image we fail to restore from

[Pavel Tikhomirov]

> These "ip addr restore < some_ip_addr_dump.img" fails because wrong
> magic in image, it is 0x666f7270 but should be 0x47361222, may be we
> somehow gave the wrong file to ip util?
> 

Finally I got reproduce on my own travis test 
https://travis-ci.org/Snorch/criu/jobs/413103226 :

========================= Run zdtm/static/env00 in ns 
==========================
Start test
./env00 --pidfile=env00.pid --outfile=env00.out --envname=ENV_00_TEST
Run criu dump
Run criu restore
Fail RESTORE failed: Error(0): Unknown
=[log]=> dump/zdtm/static/env00/85/1/restore.log
------------------------ grep Error ------------------------
(00.000031) Version: 3.10 (gitid c3ba917)
(00.000048) Running on travis-job-9486da43-0fa9-41cf-b230-af61bff5f2ac 
Linux 4.4.0-51-generic #72~14.04.1-Ubuntu SMP Thu Nov 24 19:22:30 UTC 
2016 x86_64
profiling:/home/travis/build/Snorch/criu/criu/sk-unix.gcda:Merge 
mismatch for function 26
Magic mismatch (1 elems, 666f7270 magic)
      1: Error (criu/util.c:834): exited, status=255
      1: Error (criu/net.c:1732): IP tool failed on addr restore
      1: Error (criu/net.c:1735): failed restore from image 
/home/travis/build/Snorch/criu/test/dump/zdtm/static/env00/85/1/ifaddr-9.img
      1: Error (criu/util.c:1535): Can't wait or bad status: errno=0, 
status=65280
(00.000048) Error (criu/mount.c:3273): mnt: Can't remove the directory 
/tmp/.criu.mntns.EsrXyB: No such file or directory
(00.000048) Error (criu/cr-restore.c:2308): Restoring FAILED.
------------------------ ERROR OVER ------------------------
################# Test zdtm/static/env00 FAIL at CRIU restore 
##################

The image file is right ifaddr-9.img, but why it has wrong magic, may be 
we did something wrong on dump? Will try adding more debug.