site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com Hi list, Normal (working) scenario: Traffic from mail client: Before: 192.168.1.50:50299 -> 213.213.213.213:143 Modified: 192.168.1.50:50299 -> 127.0.0.1:10143 Traffic to mail client: Before: 127.0.0.1:10143 -> 192.168.1.50:50299 Modified: 213.213.213.213:143 -> 192.168.1.50:50299 PPTP (broken) scenario: Traffic from mail client: Before: 10.214.2.34:50299 -> 213.213.213.213:143 Modified: 10.214.2.34:50299 -> 127.0.0.1:10143 BTW, here are the ipfw rules that I'm using to divert mail traffic: ipfw add 100 divert 15000 tcp from any to any 143 out ipfw add 101 divert 15000 tcp from any 143 to any in ipfw add 102 divert 15000 tcp from any to any 10143 ipfw add 103 divert 15000 tcp from any 10143 to any Thanks for any help! Jeff Cruikshank -- Jeff Cruikshank <jeff@pgp.com> Senior Software Engineer, PGP Corporation _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... I have a daemon which performs a sort of aliasing (not compltely unlike natd), to transparently proxy mail traffic between a mail client and a mailserver. For the most part, things work great, but PPTP seems to complicate matters in such a way that my packets don't get diverted to the right interface. The nature of my app is to act as a man in the middle (I know, sounds scary, but I promise it's not malicious), such that IMAP connections from the mail client automatically get redirected to my proxy app (which listens on 127.0.0.1:10143). The proxy app, in turn, connects to the mail server and proxies the traffic between the two connections, as if they were one. When things are running well, packets sent/rcvd from the mail client get processed in the following manner: The problem I'm having with PPTP would seem to be that the address translation that I perform when sending traffic back to the mail client, doesn't cause the packet to get routed correctly (this is a best guess). In my testing, the connect() call times out because the 3-way handshake can't be completed. Traffic to mail client: Before: 127.0.0.1:10143 -> 10.214.2.34:50299 After: 213.213.213.213:143 -> 10.214.2.34:50299 // Packet never received by PPTP interface with addresss 10.214.2.34 After perusing the kernel source (ip_divert.c), I thought that perhaps I could inspect (and modify) the sin_zero field of the struct sockaddr_in to control which interface the packet gets sent to (ppp0). Though I was able to get the interface name this way, changing it seemed to have no effect. I was interested to find that Apple's natd (as configured via the Internet Sharing panel) doesn't seem to work when the same PPTP connection is in place. To test this, I had another machine connect through the natd gateway to make sure it could connect to the outside world, then I had the gateway make its PPTP connection. The result was that the machine behind nat could no longer communicate with the outside world. Is there a way that I can cause the divert socket machinery to redirect a packet to a specific interface? This email sent to site_archiver@lists.apple.com