doc: Document 'dccp type' match

Add a description of dccp_pkttype and extend DCCP header expression
synopsis by the 'type' argument.

Signed-off-by: Phil Sutter <phil@nwl.cc>

2 files changed, 47 insertions, 1 deletions

diff --git a/doc/data-types.txt b/doc/data-types.txt
index a42a55fa..961fc624 100644
--- a/doc/data-types.txt
+++ b/doc/data-types.txt
@@ -492,3 +492,46 @@ For each of the types above, keywords are available for convenience:
 |==================
 
 Possible keywords for conntrack label type (ct_label) are read at runtime from /etc/connlabel.conf.
+
+DCCP PKTTYPE TYPE
+~~~~~~~~~~~~~~~~
+[options="header"]
+|==================
+|Name | Keyword | Size | Base type
+|DCCP packet type |
+dccp_pkttype |
+4 bit |
+integer
+|===================
+
+The DCCP packet type abstracts the different legal values of the respective
+four bit field in the DCCP header, as stated by RFC4340. Note that possible
+values 10-15 are considered reserved and therefore not allowed to be used. In
+iptables' *dccp* match, these values are aliased 'INVALID'. With nftables, one
+may simply match on the numeric value range, i.e. *10-15*.
+
+.keywords may be used when specifying the DCCP packet type
+[options="header"]
+|==================
+|Keyword |Value
+|request|
+0
+|response|
+1
+|data|
+2
+|ack|
+3
+|dataack|
+4
+|closereq|
+5
+|close|
+6
+|reset|
+7
+|sync|
+8
+|syncack|
+9
+|=================
diff --git a/doc/payload-expression.txt b/doc/payload-expression.txt
index ffd1b671..a593e2e7 100644
--- a/doc/payload-expression.txt
+++ b/doc/payload-expression.txt
@@ -392,7 +392,7 @@ integer (32 bit)
 DCCP HEADER EXPRESSION
 ~~~~~~~~~~~~~~~~~~~~~~
 [verse]
-*dccp* {*sport* | *dport*}
+*dccp* {*sport* | *dport* | *type*}
 
 .DCCP header expression
 [options="header"]
@@ -404,6 +404,9 @@ inet_service
 |dport|
 Destination port|
 inet_service
+|type|
+Packet type|
+dccp_pkttype
 |========================
 
 AUTHENTICATION HEADER EXPRESSION