On Friday, 18 March 2016 at 09:50:12 UTC, Marc Schütz wrote:
Looking at an strace of nmap, it seems it opens a bunch of
sockets, puts them into non-blocking mode, calls connect on
them (which will return EINPROGRESS), and then uses select(2)
to wait for them (in a loop, until all have either been
accepted or rejected). select(2) accepts a timeout value, so
you can determine how long you want to wait.
Here's an excerpt:
...
socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 50
fcntl(50, F_GETFL) = 0x2 (flags O_RDWR)
fcntl(50, F_SETFL, O_RDWR|O_NONBLOCK) = 0
setsockopt(50, SOL_SOCKET, SO_LINGER, {onoff=1, linger=0}, 8) =
0
setsockopt(50, SOL_SOCKET, SO_BINDTODEVICE, [0], 4) = -1 EPERM
(Operation not permitted)
setsockopt(50, SOL_IP, IP_TTL, [-1], 4) = 0
connect(50, {sa_family=AF_INET, sin_port=htons(32778),
sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS
(Operation now in progress)
socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 51
fcntl(51, F_GETFL) = 0x2 (flags O_RDWR)
fcntl(51, F_SETFL, O_RDWR|O_NONBLOCK) = 0
setsockopt(51, SOL_SOCKET, SO_LINGER, {onoff=1, linger=0}, 8) =
0
setsockopt(51, SOL_SOCKET, SO_BINDTODEVICE, [0], 4) = -1 EPERM
(Operation not permitted)
setsockopt(51, SOL_IP, IP_TTL, [-1], 4) = 0
connect(51, {sa_family=AF_INET, sin_port=htons(1029),
sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS
(Operation now in progress)
socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 52
fcntl(52, F_GETFL) = 0x2 (flags O_RDWR)
fcntl(52, F_SETFL, O_RDWR|O_NONBLOCK) = 0
setsockopt(52, SOL_SOCKET, SO_LINGER, {onoff=1, linger=0}, 8) =
0
setsockopt(52, SOL_SOCKET, SO_BINDTODEVICE, [0], 4) = -1 EPERM
(Operation not permitted)
setsockopt(52, SOL_IP, IP_TTL, [-1], 4) = 0
connect(52, {sa_family=AF_INET, sin_port=htons(2013),
sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS
(Operation now in progress)
select(53, [3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
43 44 45 46 47 48 49 50 51 52], [3 4 5 6 7 8 9 10 11 12 13 14
15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52], [3 4 5 6 7
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
51 52], {0, 0}) = 100 (in [3 4 5 6 7 8 9 10 11 12 13 14 15 16
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
38 39 40 41 42 43 44 45 46 47 48 49 50 51 52], out [3 4 5 6 7 8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
51 52], left {0, 0})
...
I'm pretty sure the setsockopt() calls aren't essential.
I tried:
------------------------------------------
// ...
const int MAX = 64;
Socket[] sockets = new Socket[MAX];
string ipb = "192.168.0.";
for (int i = 1; i < MAX; i++) {
string ip = ipb~to!string(i);
Socket s = new Socket(AddressFamily.INET,
std.socket.SocketType.STREAM, ProtocolType.TCP);
s.blocking = false;
sockets[i] = s;
InternetAddress ia = new InternetAddress(ip, 22);
s.connect(ia);
}
foreach (int i, Socket s; sockets)
{
SocketSet ss = new SocketSet();
//ss.add(s);
if (s.select(ss, null, null, 500.msecs) > 0)
{
writeln("\n\nDONE: ", ipb~to!string(i), ":22");
}
else
{
writeln("\n\nFAIL: ", ipb~to!string(i), ":22 is
unreachable !\n");
}
}
writeln("DONE");
------------------------------------------
When I uncomment ss.add(s); , I got the error -11.
Any suggestions ?
