Document --nowildcard option and its implications when using -m socket to intercept packets. While at it, update man page with Balazs Scheidlers comments from nf_tproxy_core.h in kernel tree to better explain how lookup is performed. Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx> Signed-off-by: Florian Westphal <fw@xxxxxxxxx> --- extensions/libxt_socket.man | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/extensions/libxt_socket.man b/extensions/libxt_socket.man index 41e8d67..2ef32ce 100644 --- a/extensions/libxt_socket.man +++ b/extensions/libxt_socket.man @@ -1,5 +1,22 @@ -This matches if an open socket can be found by doing a socket lookup on the -packet. +This matches if an open TCP/UDP socket can be found by doing a socket lookup on the +packet. It matches if there is an established or non\-zero bound listening +socket (possibly with a non\-local address). The lookup is performed using +the \fBpacket\fP tuple of TCP/UDP packets, or the original TCP/UDP header +\fBembedded\fP in an ICMP/ICPMv6 error packet. .TP \fB\-\-transparent\fP Ignore non-transparent sockets. +.TP +\fB\-\-nowildcard\fP +Do not ignore sockets bound to 'any' address. +The socket match won't accept zero\-bound listeners by default, since +then local services could intercept traffic that would otherwise be forwarded. +This option therefore has security implications when used to match traffic being +forwarded to redirect such packets to local machine with policy routing. +When using the socket match to implement fully transparent +proxies bound to non\-local addresses it is recommended to use the \-\-transparent +option instead. +.PP +Example (assuming packets with mark 1 are delivered locally): +.IP +\-t mangle \-A PREROUTING \-m socket \-\-transparent \-j MARK \-\-set\-mark 1 -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
