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For some reasons, the linux kernel has made some changes in syscalls.
As shown in src code, we pay attention to fork/vfork/clone to create
process, while exit/exit_group to kill it. From my opinion, the fork
and clone syscall should be totally different, otherwise there will
be only one syscall. However, according to the logs, I heard only
clone but no fork, exit_group but no exit. Infact, fork calls clone
and then makes some special set. They're different, fork means parents
and children, while clone means calling and callee, which allows to
share sth between caller and callee. Both fork and clone makes a new
process, pthread makes tasks and is called thread. Pid is factually
task id.
Now the 3 coroutines works well, and I've get a process tree by
map[int]*process. Here hides some questions:
- is it right for 2nd corutine to send to 3rd as long as eoe?
- how to make the delay between exit_group and deletePid clear and
suitable?
Next works:
- Change the pids from map into DataBase, which means that we
should devide front-end and back-end. Besides, when you delete
sth(such as process exit), don't delete from databese, instead
just make a tag and record their exit code. In other words, we
judge if it's alive not by entry existance but exit tag.
- Make containers recorded, for instance, rootFS, root-process,
name, id, etc.. And record them in map, maintain this database table.
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As is planed, the first coroutine throw rae event infomation to the
second, and it organizes all info for the same event accroding to
event id, which is unique without shutdown of this computer.
There's several defficuties I've encountered, so I list their solution
here to remeber:
- raw info from 1st coroutine is correct, but wrong when 2nd gets it;
or it's correct while recieved, then regular expr goes to match it,
the first match is inline with expectations, but the next match goes
totally wrong, and the info is different from what is received.
Look into the src of go-libaudit, we'll find out that when heard
from netlink socket, the read buffer is always the same slice, it
first received a long data, then **pass the origin slice to
rawEvent.Data**, and then received a shorter data. rawEvent.Data is
passed to 2nd coruntine as **a pointer to rawEvent**, which means
all this 3 process use the same part of memory. Then, when a shorter
info comes from socket, the slice won't be moved, otherwise it write
aigin to this part of mem, then coroutine 2 will get a dirty data.
To deal with it, we change the type of channel from pointer to
interface, and make a deep copy of rawEvent before passing down.
As a result, the 2nd coroutine gets a copy of message but not origin,
it finally comes right.
- While designing a regular expr, it's thought correct but miss
matched from the right string. There maybe sth wrong that can't be
discovered by people's eye, you can try to rewrite the expr, then
it may be fixed.
Also, there's some hidden dangers:
- 2nd coroutine comes with no error checks althouth err variable is
set and catched ubder the rules of compiler. we **shall** make it
later.
- Is it reasonable to pass cooked event info immediately to 3rd
coroutine without waiting some time? Info from network is out of
order after all.
Fight! Fight! Fight!
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This repo is to supervise all processes in containers, in other
words inspect behaviors of dockers, and get the pid tree.
There are several ways for programs in user space to intereact with
kernel space:
- system calls, which can be found out in source path arch/x86/syscalls
- ioctl
- /proc virtual file system, to read kernel realtime info
- nerlink socket
the pid we should pay attention to is /usr/bin/containerd, which may
come from service docker-daemon and ppid is 1. Each time a docker is
start or stop, this forks a pid, the pid then forks, that's the main
process of the docker.
To grub the info of pid create or exit, this program is based on
go-libauditd, which uses netlink socket to hear from kernel about
audit log. What's worrying is that one event is always devided into
several entries, and several events may be received alternately.
So, from my point of view, which program has 3 coroutines and 2
channels. the first receives raw event message from audit, then
throw it to channel 1; the second listen to channel 1, and organizes
each event until there's a EOE, then throw to channel 2; the third
discover event from channel 2, deal with th event, such as create or
delete pid. Specially, since two relative infomation(pid 1 fork pid2,
then pid 1 exits)may comes out of order, deletion mast be delayed for
some time(may 1 second), to keep the process tree correct.
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