[Winpcap-users] win 7 loopback adapter with winpacp pcap_sendpacket sending multicast packets

[Alberto Avanzi]

Hi,

I found some time ago a problem similar to yours, that make me think 
that yes, network behavior changed from
XP to Win7.

In my case, packets emitted on a multicast socket using standard 
winsock2 API AND with TTL=0 are NOT SEEN by winpcap
(that runs on the same host because of TTL=0). Changing TTL to 1 allows 
winpcap to receive them on the local host or on
a remote host on the same network.

This has changed from XP, where TTL=0 packets were seen and captured by 
winpcap.

Someone suggested that probably win7 does not inject datagrams with 
TLL=0 into the network adapter, but uses a
somehow different distribution system.

A.

On 02/03/2011 13:46, you yuan wrote:
> Hi,Thanks for help.
> According to the test, it's ok for transmitting on different computers.
> I have written a simple cmd program using winpcap's api to receive 
> packets from the loopback adapter. It shows capture is ok.
> So I think maybe something changed for xp and win7 loopback adapter 
> system.
> The winpcap's api and winsock's mechanism behave differently on xp and 
> win 7?
>
> On Wed, Mar 2, 2011 at 2:02 PM, Gianluca Varenni 
> <Gianluca.Varenni at riverbed.com <mailto:Gianluca.Varenni at riverbed.com>> 
> wrote:
>
>     Do the same packets get send on a standard non-loopback adapter
>     (i.e. transmitter and receiver on different computers)?
>
>     Have a nice day
>     GV
>
>     ________________________________________
>     From: winpcap-users-bounces at winpcap.org
>     <mailto:winpcap-users-bounces at winpcap.org>
>     [winpcap-users-bounces at winpcap.org
>     <mailto:winpcap-users-bounces at winpcap.org>] On Behalf Of you yuan
>     [yuanprivacy at gmail.com <mailto:yuanprivacy at gmail.com>]
>     Sent: Sunday, February 27, 2011 3:39 AM
>     To: winpcap-users at winpcap.org <mailto:winpcap-users at winpcap.org>
>     Subject: [Winpcap-users] win 7 loopback adapter with winpacp
>     pcap_sendpacket    sending multicast packets
>
>     HI,everyone
>      Recently I have come across a problem concerning winpcap sending
>      multicast packets on windows 7 loopback adapter.
>      Here have an application with two componets.One componet is a
>     simulator using winpcap to send and receive multicast packets on
>     windows networks adapters with fixed ip(i.e,192.10.x.x). Another
>     is a net module using winsock's setsockopt,ioctlsocket, recvfrom etc
>     functions to receive multicast packets sent by the first componet.
>      My problem is when I use windows 7 loopback adapter with fixed
>     ip,the first compent can send packet out(see it from the
>     wireshark), But the net module component can't receive any
>     packets. However, the same application really works on windows XP.
>      I rarely know anything winpcap packet sending mechanisms with
>     windows loopback adapter.I don't know how to fix the problem under
>     windows 7.
>      I have searched many times but gain nothing.Does anyone have the
>     similar problem or know something  or some keywords about this,
>     please help. Thanks in advance.
>
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>
>
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