Date: Sun, 08 May 2005 08:41:42 -0700 From: Maksim Yevmenkin <maksim.yevmenkin@savvis.net> To: patrickdk@patrickdk.com Cc: freebsd-net@freebsd.org Subject: Re: tap interface and locally generated packets Message-ID: <427E3336.3040907@savvis.net> In-Reply-To: <Pine.LNX.4.62.0505081401540.31842@server.dswett.patrickdk.com> References: <Pine.LNX.4.62.0505081401540.31842@server.dswett.patrickdk.com>
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Patrick, > I have been working with tap interfaces, bridging and openvpn > > Bridging works perfectly, and openvpn does too > > Packet pings from the tap interface works to any ip address, on the > local machine or computer on the bridged network > > Attempting to make a tcp connection works for bridged network, but not > the machine the tap interface is on > > I have found this is due to tcp checksums not being generated, Packets > recieved over the tap interface on the client machine have blank (bad) > checksums. > > I have looked at the source and it seems there is no interface to add > the checksums to be generated for the tap interface. tap(4) interface should not modify anything inside the packet. the whole point is to accept _complete_ ethernet frame from user-space (just as it comes from the wire) and pass it up the stack. my guess would be that something else is not generating proper ip checksum. just a crazy thought: are you offloading ip checksum'ing to your ethernet card? if so, please try to disable it and see if it helps. thanks, max
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