1 This is used to send back an error packet in response to the matched 2 packet: otherwise it is equivalent to 3 .B DROP 4 so it is a terminating TARGET, ending rule traversal. 5 This target is only valid in the 6 .BR INPUT , 7 .B FORWARD 8 and 9 .B OUTPUT 10 chains, and user-defined chains which are only called from those 11 chains. The following option controls the nature of the error packet 12 returned: 13 .TP 14 \fB\-\-reject\-with\fP \fItype\fP 15 The type given can be 16 \fBicmp\-net\-unreachable\fP, 17 \fBicmp\-host\-unreachable\fP, 18 \fBicmp\-port\-unreachable\fP, 19 \fBicmp\-proto\-unreachable\fP, 20 \fBicmp\-net\-prohibited\fP, 21 \fBicmp\-host\-prohibited\fP or 22 \fBicmp\-admin\-prohibited\fP (*) 23 which return the appropriate ICMP error message (\fBport\-unreachable\fP is 24 the default). The option 25 \fBtcp\-reset\fP 26 can be used on rules which only match the TCP protocol: this causes a 27 TCP RST packet to be sent back. This is mainly useful for blocking 28 .I ident 29 (113/tcp) probes which frequently occur when sending mail to broken mail 30 hosts (which won't accept your mail otherwise). 31 .PP 32 (*) Using icmp\-admin\-prohibited with kernels that do not support it will result in a plain DROP instead of REJECT 33
