Assert in nsock_pcap.c with iocp engine

[gvanem]

With a command like:

nmap -p20-80 -sV --nsock-engine=iocp 10.0.0.1

I always get an assert-error in nsock/src/engine_ioc.p.c at line 237:

Assertion failed: result, file engine_iocp.c, line 237

Further studying shows CreateIoCompletionPort() returns 0 with GetLastError() == 87.
Which is ERROR_INVALID_PARAMETER. Not sure why, but is iod->sd a legal value for a HANDLE?

This is on Win-10, latest Nmap built using MSVC-2015, 32-bit.

[dmiller-nmap]

HANDLE is typedef'd PVOID, and iod->sd is an int. Generally those will be compatible in terms of storage size, but I can see how it might be a stretch to cast one to the other. Hopefully @Tudor-Coman or @bmenrigh can comment.

[gvanem]

Further tracing shows it correctly uses the socket-value of 1216 from WSASocketA(). So maybe another parameter it to blame?

I can also see there are 2 completion-ports used at the same time; iocp_init() is called twice. Doesn't look right. It's also strange to me that a command:

nmap -p20-80 -sT --nsock-engine=iocp 10.0.0.1

doesn't involve IOCP (only select() is used).

[gvanem]

My bad, I hadn't got the updated nbase_misc.c with the overlapped flag:

return WSASocket(af, style, protocol, NULL, 0, WSA_FLAG_OVERLAPPED);

Hence it's working now. I'll close the issue.

[gvanem]

There is still a bug regarding this. Now with a different assert() in nsock_pcap.c:

Starting Nping 0.7.40SVN ( https://nmap.org/nping ) at 2017-06-01 04:39 PDT
SENT (0.3125s) TCP 10.0.0.10:22594 > 10.0.0.1:80 S ttl=64 id=44422 iplen=40  seq=2582998811 win=1480
Assertion failed: fs_length(&(nse->iobuf)) == 0, file nsock_pcap.c, line 392

From a command like nping --tcp --nsock-engine=iocp 10.0.0.1.
And the call-stack:

ucrtbase!_wassert+0x16
nping!do_actual_pcap_read(struct nevent * nse = 0x04838cb0)+0x89
nping!pcap_read_on_nonselect(struct npool * nsp = 0x015ae110)+0x1c
nping!iocp_loop(struct npool * nsp = 0x015ae110, int msec_timeout = 0n986)+0x10a
nping!nsock_engine_loop+0xa
nping!nsock_loop(struct npool * nsp = 0x015ae110, int msec_timeout = 0n1001)+0x175

nping!ProbeMode::start(void)+0x7c6
nping!main(int argc = 0n4, char ** argv = 0x03ccfaf8)+0x236

PS. It would be nice if the available engines was listed in nping --help or nping --version.

PS2. I see there is an insane amount of WSAEINVAL returned from WSAPoll() when using a
command like nping --nsock-engine=poll 10.0.0.1.

[gvanem]

Just removing the assert() in nsock_pcap.c, line 392, all seems to work on Windows too.
I've no idea what this means, but the nse->iobuf contains some junk at that point.