> On 09.01.2018 12:28, O. Hartmann wrote: > > In section RULE OPTIONS, there is recv|xmit|via explained (a bit). There is > > also an example: > > > > ipfw add deny ip from any to any out recv ed0 xmit ed1 > > > > Can someone explain a bit more what the semantics of these is? I get > > especially > > confused by the subsequent blocks of text following the line I mentioned > > above. > > Since not everybody using FreeBSD is capable of studying the kernel > > sources, I > > have difficulties to put those statements in line with a visualization of > > the > > packet flow. A local host receiving a packets destined for the local host > > can > > not have xmit interface? If I imagine, that the recv interface might be the > > interface adjacent directly to the in/out port depicted in section PACKET > > FLOW > > it doesn't give me any idea why there is no xmit interface. > > When your system has two interfaces ed0 and ed1, and it acts as router, > a forwarded packet can be checked by firewall two times: > > 1. When a packet is received on ed0 interface, mbuf associated with this > packet gets a property "receiving interface". This packet is checked for > inbound direction and can be matched by "in" and "recv ed0" opcodes.
in, recv and via options > If it was not dropped by rules, it will go through IP stack and can be > forwarded according to routing table via interface ed1. > > 2. When the routing decision was made (i.e. outbound interface is > determined) a packet checked by firewall again, now for outbound > direction. And it can be matched by "out" and "xmit ed1" opcodes. The in, recv and via options > opcode "recv ed0" still can be matched too, but "in" opcode will not > matched. > > A packet destined for local host is consumed by local IP stack and will > not forwarded. It is checked by firewall only one time (usually). Thus > it can not have xmit interface. And a packet generated localy would not have a recv interface. > -- > WBR, Andrey V. Elsukov > -- Rod Grimes rgri...@freebsd.org _______________________________________________ freebsd-ipfw@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-ipfw To unsubscribe, send any mail to "freebsd-ipfw-unsubscr...@freebsd.org"