libxt_TOS.man revision 3b7a22b44d74b9b05d5e4b0529ebf72c49dcbff5 
1This module sets the Type of Service field in the IPv4 header (including the
2"precedence" bits) or the Priority field in the IPv6 header. Note that TOS
3shares the same bits as DSCP and ECN. The TOS target is only valid in the
4\fBmangle\fP table.
5.TP
6\fB\-\-set\-tos\fP \fIvalue\fP[\fB/\fP\fImask\fP]
7Zeroes out the bits given by \fImask\fP (see NOTE below) and XORs \fIvalue\fP
8into the TOS/Priority field. If \fImask\fP is omitted, 0xFF is assumed.
9.TP
10\fB\-\-set\-tos\fP \fIsymbol\fP
11You can specify a symbolic name when using the TOS target for IPv4. It implies
12a mask of 0xFF (see NOTE below). The list of recognized TOS names can be
13obtained by calling iptables with \fB\-j TOS \-h\fP.
14.PP
15The following mnemonics are available:
16.TP
17\fB\-\-and\-tos\fP \fIbits\fP
18Binary AND the TOS value with \fIbits\fP. (Mnemonic for \fB\-\-set\-tos
190/\fP\fIinvbits\fP, where \fIinvbits\fP is the binary negation of \fIbits\fP.
20See NOTE below.)
21.TP
22\fB\-\-or\-tos\fP \fIbits\fP
23Binary OR the TOS value with \fIbits\fP. (Mnemonic for \fB\-\-set\-tos\fP
24\fIbits\fP\fB/\fP\fIbits\fP. See NOTE below.)
25.TP
26\fB\-\-xor\-tos\fP \fIbits\fP
27Binary XOR the TOS value with \fIbits\fP. (Mnemonic for \fB\-\-set\-tos\fP
28\fIbits\fP\fB/0\fP. See NOTE below.)
29.PP
30NOTE: In Linux kernels up to and including 2.6.38, with the exception of
31longterm releases 2.6.32.42 (or later) and 2.6.33.15 (or later), there is a bug
32whereby IPv6 TOS mangling does not behave as documented and differs from the
33IPv4 version. The TOS mask indicates the bits one wants to zero out, so it needs
34to be inverted before applying it to the original TOS field. However, the
35aformentioned kernels forgo the inversion which breaks --set-tos and its
36mnemonics.
37