Date: Wed, 19 Oct 2016 03:03:58 +1100 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: Shawn Bakhtiar <shashaness@hotmail.com> Cc: Samira Nazari <nazari.s11@gmail.com>, "freebsd-ipfw@freebsd.org" <freebsd-ipfw@freebsd.org> Subject: Re: change packets with IPFW divert Message-ID: <20161019023739.D6806@sola.nimnet.asn.au> In-Reply-To: <CY1PR14MB052039CE53AE379BF6693C5DC4D30@CY1PR14MB0520.namprd14.prod.outlook.com> References: <CAG1-nfyJ0LRsFH1xMZJhfkLC8GgLSgTukOdD%2B2-xLqLx8FWrBw@mail.gmail.com> <CY1PR14MB052039CE53AE379BF6693C5DC4D30@CY1PR14MB0520.namprd14.prod.outlook.com>
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On Tue, 18 Oct 2016 14:21:50 +0000, Shawn Bakhtiar wrote: > On Oct 18, 2016, at 6:49 AM, Samira Nazari <nazari.s11@gmail.com<mailto:nazari.s11@gmail.com>> wrote: > > Hello every one, > > When we diverte packets to the specified port with "IPFW divert" , > > we can change it and re-sent to the kernel? > Not sure what you mean by change it but: > > "Divert sockets are similar to raw IP sockets, except that they can > be bound to a specific divert port via the bind(2) system call. The > IP address in the bind is ignored; only the port number is > significant. A divert socket bound to a divert port will receive all > packets diverted to that port by some (here unspecified) kernel > mechanism(s). Packets may also be written to a divert port, in which > case they re-enter kernel IP packet processing." > > -- SRC: https://www.freebsd.org/cgi/man.cgi?query=divert&sektion=4&apropos=0&manpath=FreeBSD+10.3-RELEASE+and+Ports Apart from divert(4), most likely the best example is the natd(8) code, which modifies packet source or destination addresses and (maybe) ports. Ignoring the NAT processing - or not, as appropriate - the way natd uses divert sockets both to receive packets from ipfw and later (perhaps) to reinject them for further processing should show clearly how it's done. cheers, Ian
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