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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 14:18:53 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 14:18:53 +0000 |
commit | a0e0018c9a7ef5ce7f6d2c3ae16aecbbd16a8f67 (patch) | |
tree | 8feaf1a1932871b139b3b30be4c09c66489918be /man/man8/tc-nat.8 | |
parent | Initial commit. (diff) | |
download | iproute2-upstream.tar.xz iproute2-upstream.zip |
Adding upstream version 6.1.0.upstream/6.1.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'man/man8/tc-nat.8')
-rw-r--r-- | man/man8/tc-nat.8 | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/man/man8/tc-nat.8 b/man/man8/tc-nat.8 new file mode 100644 index 0000000..f3b17ef --- /dev/null +++ b/man/man8/tc-nat.8 @@ -0,0 +1,78 @@ +.TH "NAT action in tc" 8 "12 Jan 2015" "iproute2" "Linux" + +.SH NAME +nat - stateless native address translation action +.SH SYNOPSIS +.in +8 +.ti -8 +.BR tc " ... " "action nat" +.I DIRECTION OLD NEW + +.ti -8 +.IR DIRECTION " := { " +.BR ingress " | " egress " }" + +.ti -8 +.IR OLD " := " IPV4_ADDR_SPEC + +.ti -8 +.IR NEW " := " IPV4_ADDR_SPEC + +.ti -8 +.IR IPV4_ADDR_SPEC " := { " +.BR default " | " any " | " all " | " +\fIin_addr\fR[\fB/\fR{\fIprefix\fR|\fInetmask\fR}] +.SH DESCRIPTION +The +.B nat +action allows one to perform NAT without the overhead of conntrack, which is +desirable if the number of flows or addresses to perform NAT on is large. This +action is best used in combination with the +.B u32 +filter to allow for efficient lookups of a large number of stateless NAT rules +in constant time. +.SH OPTIONS +.TP +.B ingress +Translate destination addresses, i.e. perform DNAT. +.TP +.B egress +Translate source addresses, i.e. perform SNAT. +.TP +.I OLD +Specifies addresses which should be translated. +.TP +.I NEW +Specifies addresses which +.I OLD +should be translated into. +.SH NOTES +The accepted address format in +.IR OLD " and " NEW +is quite flexible. It may either consist of one of the keywords +.BR default ", " any " or " all , +representing the all-zero IP address or a combination of IP address and netmask +or prefix length separated by a slash +.RB ( / ) +sign. In any case, the mask (or prefix length) value of +.I OLD +is used for +.I NEW +as well so that a one-to-one mapping of addresses is assured. + +Address translation is done using a combination of binary operations. First, the +original (source or destination) address is matched against the value of +.IR OLD . +If the original address fits, the new address is created by taking the leading +bits from +.I NEW +(defined by the netmask of +.IR OLD ) +and taking the remaining bits from the original address. + +There is rudimental support for upper layer protocols, namely TCP, UDP and ICMP. +While for the first two only checksum recalculation is performed, the action +also takes care of embedded IP headers in ICMP packets by translating the +respective address therein, too. +.SH SEE ALSO +.BR tc (8) |