Add translation for dccp to nftables.

Full translation of this match awaits the support for --dccp-option.
Also, since inversion of set is not possible in nftables, using dccp
with rules like
...dccp type != {request, response}..
is going to throw errors.

Examples:

$ sudo iptables-translate -A INPUT -p dccp -m dccp --sport 100
nft add rule ip filter INPUT dccp sport 100 counter

$ sudo iptables-translate -A INPUT -p dccp -m dccp --dport 100:200
nft add rule ip filter INPUT dccp dport 100-200 counter

$ sudo iptables-translate -A INPUT -p dccp -m dccp ! --dport 100
nft add rule ip filter INPUT dccp dport != 100 counter

$ sudo iptables-translate -A INPUT -p dccp -m dccp --dccp-type REQUEST,RESPONSE
nft add rule ip filter INPUT dccp type {request, response} counter

Signed-off-by: Shivani Bhardwaj <shivanib...@gmail.com>
---
 extensions/libxt_dccp.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)

diff --git a/extensions/libxt_dccp.c b/extensions/libxt_dccp.c
index a35cabb..27dd625 100644
--- a/extensions/libxt_dccp.c
+++ b/extensions/libxt_dccp.c
@@ -277,6 +277,93 @@ static void dccp_save(const void *ip, const struct 
xt_entry_match *match)
        }
 }
 
+static const char *const dccp_pkt_types_xlate[] = {
+       [DCCP_PKT_REQUEST]      = "request",
+       [DCCP_PKT_RESPONSE]     = "response",
+       [DCCP_PKT_DATA]         = "data",
+       [DCCP_PKT_ACK]          = "ack",
+       [DCCP_PKT_DATAACK]      = "dataack",
+       [DCCP_PKT_CLOSEREQ]     = "closereq",
+       [DCCP_PKT_CLOSE]        = "close",
+       [DCCP_PKT_RESET]        = "reset",
+       [DCCP_PKT_SYNC]         = "sync",
+       [DCCP_PKT_SYNCACK]      = "syncack",
+       [DCCP_PKT_INVALID]      = "invalid",
+};
+
+static void
+print_types_xlate(uint16_t types, struct xt_xlate *xl, int numeric)
+{
+       bool have_type = false, set_need = false;
+
+       if (types > 1) {
+               xt_xlate_add(xl, "{");
+               set_need = true;
+       }
+
+       while (types) {
+               unsigned int i;
+
+               for (i = 0; !(types & (1 << i)); i++);
+
+               if (have_type)
+                       xt_xlate_add(xl, ", ");
+               else
+                       have_type = true;
+
+               if (numeric)
+                       xt_xlate_add(xl, "%u", i);
+               else
+                       xt_xlate_add(xl, "%s", dccp_pkt_types_xlate[i]);
+
+               types &= ~(1 << i);
+       }
+
+       if (set_need)
+               xt_xlate_add(xl, "}");
+
+       xt_xlate_add(xl, " ");
+}
+
+static int dccp_xlate(const struct xt_entry_match *match,
+                     struct xt_xlate *xl, int numeric)
+{
+       const struct xt_dccp_info *einfo =
+               (const struct xt_dccp_info *)match->data;
+
+       xt_xlate_add(xl, "dccp ");
+
+       if (einfo->flags & XT_DCCP_SRC_PORTS) {
+               if (einfo->spts[0] != einfo->spts[1])
+                       xt_xlate_add(xl, "sport%s %u-%u ",
+                                    einfo->invflags & XT_DCCP_SRC_PORTS ? " 
!=" : "",
+                                    einfo->spts[0], einfo->spts[1]);
+               else
+                       xt_xlate_add(xl, "sport%s %u ",
+                                    einfo->invflags & XT_DCCP_SRC_PORTS ? " 
!=" : "",
+                                    einfo->spts[0]);
+       }
+
+       if (einfo->flags & XT_DCCP_DEST_PORTS) {
+               if (einfo->dpts[0] != einfo->dpts[1])
+                       xt_xlate_add(xl, "dport%s %u-%u ",
+                                    einfo->invflags & XT_DCCP_DEST_PORTS ? " 
!=" : "",
+                                    einfo->dpts[0], einfo->dpts[1]);
+               else
+                       xt_xlate_add(xl, "dport%s %u ",
+                                    einfo->invflags & XT_DCCP_DEST_PORTS ? " 
!=" : "",
+                                    einfo->dpts[0]);
+       }
+
+       if (einfo->flags & XT_DCCP_TYPE) {
+               xt_xlate_add(xl, "type%s ",
+                            einfo->invflags & XT_DCCP_TYPE ? " !=" : "");
+               print_types_xlate(einfo->typemask, xl, 0);
+       }
+
+       return 1;
+}
+
 static struct xtables_match dccp_match = {
        .name           = "dccp",
        .family         = NFPROTO_UNSPEC,
@@ -288,6 +375,7 @@ static struct xtables_match dccp_match = {
        .save           = dccp_save,
        .x6_parse       = dccp_parse,
        .x6_options     = dccp_opts,
+       .xlate          = dccp_xlate,
 };
 
 void _init(void)
-- 
1.9.1

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