无法连接到python中的抽象unix套接字 [英] Can not connect to an abstract unix socket in python
问题描述
我有一个用c ++编写的服务器，它创建并绑定到一个名为空间地址为\0hidden的抽象unix套接字。我也有一个用c ++编写的客户端，这个客户端可以成功连接到我的服务器。 BTW，我没有这个客户端的源代码。现在我试图连接到我的服务器使用客户端我写在python没有成功。我不明白为什么我的python客户端不工作。我发布了我的服务器和客户端代码的相关部分。
服务器
#define UD_SOCKET_PATH\0hidden
struct sockaddr_un addr;
int fd，cl;
if（（fd = socket（AF_UNIX，SOCK_STREAM，0））== -1）
{
syslog（LOG_CRIT，Error creating socket！
exit（1）;
}
memset（& addr，0，sizeof（addr））;
addr.sun_family = AF_UNIX;
strncpy（addr.sun_path，UD_SOCKET_PATH，sizeof（addr.sun_path）-1）;
unlink（UD_SOCKET_PATH）;
if（:: bind（fd，（struct sockaddr *）& addr，sizeof（addr））== -1）
{
syslog LOG_CRIT，Bind error）;
exit（1）;
}
if（listen（fd，MAX_CONN_PENDING）== -1）
{
syslog（LOG_CRIT，Listen error）;
exit（1）;
}
syslog（LOG_INFO，开始侦听）;
和我的客户代码
＃！ / opt / python / bin / python
import os
import socket
import sys
＃创建UDS套接字
sock = socket.socket（socket.AF_UNIX，socket .SOCK_STREAM）
server_address =\0hidden
print>> sys.stderr，'连接到％s'％server_address.decode（utf-8）
try：
sock.connect（server_address）
除了socket.error，msg：
print>> sys.stderr，msg
sys.exit（1）
运行客户端后，我得到以下错误输出：
连接到隐藏
[Errno 111]连接被拒绝
对于一些额外的信息，我发布我的工作的c ++客户端和非工作的python客户端的strace输出的相关部分：
工作c ++客户端：
socket（PF_FILE，SOCK_STREAM，0）= 3
connect（3，{sa_family = AF_FILE，path = @ $
mmap2（NULL，4096，0）= 0
mmap2（1，{st_mode = S_IFCHR | 0620，st_rdev = makedev（136，0），...} PROT_READ | PROT_WRITE，MAP_PRIVATE | MAP_ANONYMOUS，-1,0）= 0xb77d7000
write（1，发送消息是：00014 www.googl...，38）= 38
write 00014 www.google.com，20）= 20
recv（3，014 Search Engines，99,0）= 18
write（1，014 Search Engines\\\
，19 ）= 19
close（3）= 0
exit_group（0）=？
无法使用python客户端：
socket（PF_FILE，SOCK_STREAM，0）= 3
connect（3，{sa_family = AF_FILE，path = @hidden...}，9）= -1 ECONNREFUSED拒绝）
write（2，Traceback（most recent call last...，35）= 35
write（2，File \./ uds.py\，line 13 ，in <...，40）= 40
open（./ uds.py，O_RDONLY | O_LARGEFILE）= 4
fstat64（4，{st_mode = S_IFREG | 0755，st_size = 839，...}）= 0
mmap2（NULL，4096，PROT_READ | PROT_WRITE，MAP_PRIVATE | MAP_ANONYMOUS，-1,0）= 0xb7792000
read（4，＃！/ opt / python / bin / python \\\
import...，4096）= 839
write（2，，4）= 4
write（2，sock.connect（'\\0hidden' ）\\\
，25）= 25
close（4）= 0
munmap（0xb7792000，4096）= 0
write（2，File \/ opt / python / lib / python2。...，64）= 64
open（/ opt / python / lib / python2.7 / socket.py，O_RDONLY | O_LARGEFILE）= 4
fstat64 {st_mode = S_IFREG | 0755，st_size = 20234，...}）= 0
mmap2（NULL，4096，PROT_READ | PROT_WRITE，MAP_PRIVATE | MAP_ANONYMOUS，-1,0）= 0xb7792000
read ，＃Wrapper module for _socket，pr...，4096）= 4096
read（4，oo long.\\\\
errorTab [10064] =...，4096）= 4096
write（2，，4）= 4
write（2，return getattr（self._sock，name）（...，39）= 39
close ）= 0
munmap（0xb7792000，4096）= 0
write（2，socket，6）= 6
write（2，。，1）= 1
写入（2，错误，5）= 5
写入（2，：，2）= 2
写入（2，[Errno 111] Connection refused，30）= 30
write（2，\\\
，1）= 1
rt_sigaction（SIGINT，{SIG_DFL，[]，0}，{0x810fbe0，[]，0}，8）= 0
close（3）= 0
exit_group（1）=？
并且当我运行我的c ++客户端时，我从服务器得到这个strace输出：
0，NULL）= 12
futex（0x80646a4，FUTEX_CMP_REQUEUE_PRIVATE，1，2147483647，0x8064688，360）= 10
futex（0x8064688，FUTEX_WAKE_PRIVATE，1）= 1
接受（5，
我运行我的python客户端，没有输出显示strace。所以看起来我试图连接到一个错误的地址，但我的地址定义为\0hidden
你的C ++并不是你想象的那样，这行：
strncpy（addr.sun_path，UD_SOCKET_PATH，sizeof（addr.sun_path）-1）;
将单个空字符'\0'复制到 addr.sun_path 。注意 strncpy（）的联机帮助页中的这一行：
< >
如果src的长度小于n，strncpy（）将额外的
字节写入dest以确保写入总共n个字节。
因此，你的C ++实际上连接到一个抽象域套接字\0。 Python在这里做正确的事，并连接到\0hidden上的抽象域套接字。
I have a server written in c++ which creates and binds to an abstract unix socket with a namespace address of "\0hidden". I also have a client which is written in c++ also and this client can successfully connect to my server. BTW, I do not have the source code of this client. Now I am trying to connect to my server using a client I have written in python with no success. I do not understand why my python client is not working. I am posting the relevant parts of my server and client codes.
Server
#define UD_SOCKET_PATH "\0hidden"
struct sockaddr_un addr;
int fd,cl;
if ( (fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
{
syslog(LOG_CRIT, "Error creating socket!");
exit(1);
}
memset(&addr, 0, sizeof(addr));
addr.sun_family = AF_UNIX;
strncpy(addr.sun_path, UD_SOCKET_PATH, sizeof(addr.sun_path)-1);
unlink(UD_SOCKET_PATH);
if (::bind(fd, (struct sockaddr*)&addr, sizeof(addr)) == -1)
{
syslog(LOG_CRIT, "Bind error");
exit(1);
}
if (listen(fd, MAX_CONN_PENDING) == -1)
{
syslog(LOG_CRIT, "Listen error");
exit(1);
}
syslog(LOG_INFO, "Start listening.");
And my client code
#! /opt/python/bin/python
import os
import socket
import sys
# Create a UDS socket
sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
server_address = "\0hidden"
print >>sys.stderr, 'connecting to %s' % server_address.decode("utf-8")
try:
sock.connect(server_address)
except socket.error, msg:
print >>sys.stderr, msg
sys.exit(1)
After running the client I get the following error output:
connecting to hidden
[Errno 111] Connection refused
And for some extra information I am posting the relevant parts of the strace outputs of my working c++ client and non-working python client:
Working c++ client:
socket(PF_FILE, SOCK_STREAM, 0) = 3
connect(3, {sa_family=AF_FILE, path=@""}, 110) = 0
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb77d7000
write(1, "Sent message is: 00014 www.googl"..., 38) = 38
write(3, "00014 www.google.com", 20) = 20
recv(3, "014 Search Engines", 99, 0) = 18
write(1, "014 Search Engines\n", 19) = 19
close(3) = 0
exit_group(0) = ?
None working python client:
socket(PF_FILE, SOCK_STREAM, 0) = 3
connect(3, {sa_family=AF_FILE, path=@"hidden"...}, 9) = -1 ECONNREFUSED (Connection refused)
write(2, "Traceback (most recent call last"..., 35) = 35
write(2, " File \"./uds.py\", line 13, in <"..., 40) = 40
open("./uds.py", O_RDONLY|O_LARGEFILE) = 4
fstat64(4, {st_mode=S_IFREG|0755, st_size=839, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7792000
read(4, "#! /opt/python/bin/python\nimport"..., 4096) = 839
write(2, " ", 4) = 4
write(2, "sock.connect('\\0hidden')\n", 25) = 25
close(4) = 0
munmap(0xb7792000, 4096) = 0
write(2, " File \"/opt/python/lib/python2."..., 64) = 64
open("/opt/python/lib/python2.7/socket.py", O_RDONLY|O_LARGEFILE) = 4
fstat64(4, {st_mode=S_IFREG|0755, st_size=20234, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7792000
read(4, "# Wrapper module for _socket, pr"..., 4096) = 4096
read(4, "oo long.\"\n errorTab[10064] = "..., 4096) = 4096
write(2, " ", 4) = 4
write(2, "return getattr(self._sock,name)("..., 39) = 39
close(4) = 0
munmap(0xb7792000, 4096) = 0
write(2, "socket", 6) = 6
write(2, ".", 1) = 1
write(2, "error", 5) = 5
write(2, ": ", 2) = 2
write(2, "[Errno 111] Connection refused", 30) = 30
write(2, "\n", 1) = 1
rt_sigaction(SIGINT, {SIG_DFL, [], 0}, {0x810fbe0, [], 0}, 8) = 0
close(3) = 0
exit_group(1) = ?
And also when I run my c++ client, I get this strace output from my server:
0, NULL) = 12
futex(0x80646a4, FUTEX_CMP_REQUEUE_PRIVATE, 1, 2147483647, 0x8064688, 360) = 10
futex(0x8064688, FUTEX_WAKE_PRIVATE, 1) = 1
accept(5,
But when I run my python client, no output is shown on strace. So it seems like I am trying to connect to a wrong address, but my address is defined as "\0hidden" in both my server and my client.
Your C++ doesn't do quite what you think it does. This line:
strncpy(addr.sun_path, UD_SOCKET_PATH, sizeof(addr.sun_path)-1);
Copies a single null character '\0' into addr.sun_path. Note this line in the manpage for strncpy():
If the length of src is less than n, strncpy() writes additional null bytes to dest to ensure that a total of n bytes are written.
As a result your C++ actually connects to an abstract domain socket at "\0". Python does the right thing here and connects to an abstract domain socket at "\0hidden".
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