From b820d892a6914104a0ecb3af9fa287e693a4f90c Mon Sep 17 00:00:00 2001 From: cinap_lenrek Date: Sun, 15 Dec 2019 13:59:08 +0100 Subject: ip(3): document special null-address hack for accepting all incoming connections --- sys/man/3/ip | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/sys/man/3/ip b/sys/man/3/ip index 72a7ea7fa..031d5eca9 100644 --- a/sys/man/3/ip +++ b/sys/man/3/ip @@ -185,6 +185,22 @@ ARP requests for the remote address. .IR Ppp (8) does this to make remote machines appear to be connected to the local Ethernet. +Adding the special null-address +.B "0.0.0.0" +or +.B "::" +in +.I local +to a interface makes the ip stack accept all incoming +connections regardless of the destination IP address. +This is used temporarily by +.IR ipconfig (8) +to accept DHCP answers when no IP address +has been assigned yet. This can also be used +to implement a NAT gateway by accepting all +incoming connections and proxying them with +.IR trampoline (8) +to a different ip stack. .TP .BI remove\ "local mask" Remove a local IP address from an interface. -- cgit v1.2.3