[issue25541] Wrong usage of sockaddr_un struct for abstract namespace unix sockets
PrzemeK added the comment:
Yep, it was 3.4 then... but I think problem still exists
tl;dr: For abstract sockets (only?) filling struct with zeros is
meaningful.
long:
* Python (cli) -> Python (srv) = works
* C (cli) -> C (srv) = works
* C (cli) -> Python (srv) = does NOT work
* Python (cli) -> C (srv) = does NOT work (strace dumps below)
$ gcc --version
gcc (Ubuntu 7.4.0-1ubuntu1~18.04) 7.4.0
$ uname -a
Linux ajzus 4.15.0-48-generic #51-Ubuntu SMP Wed Apr 3 08:28:49 UTC 2019 x86_64
x86_64 x86_64 GNU/Linux
$ python3.7 --version
Python 3.7.1
// 1st console
$ gcc -g -Wall -Wextra -pedantic -o abs_srv abs_srv.c
$ strace ./abs_srv
...
socket(AF_UNIX, SOCK_STREAM, 0) = 3
bind(3, {sa_family=AF_UNIX,
sun_path=@"/var/tmp/sock.tmp\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"},
110) = 0
listen(3, 5)= 0
accept(3, NULL, NULL
// waiting
// 2nd console
$ ls /var/tmp/*.sock
ls: cannot access '/var/tmp/*.sock': No such file or directory
$ strace python3.7 abs_cli.py
...
socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0) = 3
connect(3, {sa_family=AF_UNIX, sun_path=@"/var/tmp/sock.tmp"}, 20) = -1
ECONNREFUSED (Connection refused)
--
versions: +Python 3.7
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[issue25541] Wrong usage of sockaddr_un struct for abstract namespace unix sockets
PrzemeK added the comment:
Gist: https://gist.github.com/soutys/ffbe2e76a86835a9cc6b
More:
Padding `sun_path` with zeros for python cli code:
...
client = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
client.connect("\0/var/tmp/sock.tmp" + "\0" * 90)
...
gives strace like:
...
socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0) = 3
connect(3, {sa_family=AF_UNIX,
sun_path=@"/var/tmp/sock.tmp\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"},
110) = 0
write(1, "Ready.\n", 7Ready.
) = 7
...
= works
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[issue25541] Wrong usage of sockaddr_un struct for abstract namespace unix sockets
Changes by PrzemeK : -- components: IO, Library (Lib) nosy: soutys priority: normal severity: normal status: open title: Wrong usage of sockaddr_un struct for abstract namespace unix sockets type: behavior versions: Python 2.7, Python 3.4 ___ Python tracker <http://bugs.python.org/issue25541> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue25541] Wrong usage of sockaddr_un struct for abstract namespace unix sockets
New submission from PrzemeK:
Case:
http://stackoverflow.com/questions/33465094/connection-refused-when-using-abstract-namespace-unix-sockets
The code that does not work (python3 example):
...
sock_path = b"/var/tmp/sock.tmp"
server.bind(b"\0" + sock_path)
...
and strace shows:
connect(3, {sa_family=AF_LOCAL, sun_path=@"/var/tmp/sock.tmp"}, 20) = -1
ECONNREFUSED (Connection refused)
For C-written client strace shows:
connect(3, {sa_family=AF_LOCAL, sun_path=@"/var/tmp/sock.tmp"}, 110) = 0
The code that actually works (python3 example):
...
sun_path_len = 108
sock_path = b"/var/tmp/sock.tmp"
server.bind(b"\0" + sock_path + (b"\0" * (sun_path_len - len(sock_path) - 1)))
...
and strace shows:
bind(3, {sa_family=AF_LOCAL, sun_path=@"/var/tmp/sock.tmp"}, 110) = 0
110 it's the correst size of a struct.
There's no hint at
https://docs.python.org/3/library/socket.html#socket-families for that.
Test files (servers and clients):
https://gist.github.com/soutys/ffbe2e76a86835a9cc6b
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[issue25541] Wrong usage of sockaddr_un struct for abstract namespace unix sockets
PrzemeK added the comment:
Errata - 1st paragraph should be:
The code that does not work (python3 example):
...
sock_path = b"/var/tmp/sock.tmp"
server.bind(b"\0" + sock_path)
...
and strace shows:
bind(3, {sa_family=AF_LOCAL, sun_path=@"/var/tmp/sock.tmp"...}, 20) = 0
--
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