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- This module sets the Type of Service field in the IPv4 header (including the
- "precedence" bits) or the Priority field in the IPv6 header. Note that TOS
- shares the same bits as DSCP and ECN. The TOS target is only valid in the
- \fBmangle\fP table.
- .TP
- \fB\-\-set\-tos\fP \fIvalue\fP[\fB/\fP\fImask\fP]
- Zeroes out the bits given by \fImask\fP (see NOTE below) and XORs \fIvalue\fP
- into the TOS/Priority field. If \fImask\fP is omitted, 0xFF is assumed.
- .TP
- \fB\-\-set\-tos\fP \fIsymbol\fP
- You can specify a symbolic name when using the TOS target for IPv4. It implies
- a mask of 0xFF (see NOTE below). The list of recognized TOS names can be
- obtained by calling iptables with \fB\-j TOS \-h\fP.
- .PP
- The following mnemonics are available:
- .TP
- \fB\-\-and\-tos\fP \fIbits\fP
- Binary AND the TOS value with \fIbits\fP. (Mnemonic for \fB\-\-set\-tos
- 0/\fP\fIinvbits\fP, where \fIinvbits\fP is the binary negation of \fIbits\fP.
- See NOTE below.)
- .TP
- \fB\-\-or\-tos\fP \fIbits\fP
- Binary OR the TOS value with \fIbits\fP. (Mnemonic for \fB\-\-set\-tos\fP
- \fIbits\fP\fB/\fP\fIbits\fP. See NOTE below.)
- .TP
- \fB\-\-xor\-tos\fP \fIbits\fP
- Binary XOR the TOS value with \fIbits\fP. (Mnemonic for \fB\-\-set\-tos\fP
- \fIbits\fP\fB/0\fP. See NOTE below.)
- .PP
- NOTE: In Linux kernels up to and including 2.6.38, with the exception of
- longterm releases 2.6.32 (>=.42), 2.6.33 (>=.15), and 2.6.35 (>=.14), there is
- a bug whereby IPv6 TOS mangling does not behave as documented and differs from
- the IPv4 version. The TOS mask indicates the bits one wants to zero out, so it
- needs to be inverted before applying it to the original TOS field. However, the
- aformentioned kernels forgo the inversion which breaks --set-tos and its
- mnemonics.
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