work in progress - implementing the dns cookie support in mio_svc_dnc_resolve()

mio/bin/t01.c

@@ -1281,7 +1281,7 @@ if (!mio_svc_dnc_resolve(dnc, "b.wild.com", MIO_DNS_RRT_A, MIO_SVC_DNC_RESOLVE_F
 	printf ("resolve attempt failure ---> a.wild.com\n");
 }
 
-if (!mio_svc_dnc_resolve(dnc, "www.microsoft.com", MIO_DNS_RRT_CNAME, 0, on_dnc_resolve, 0))
+if (!mio_svc_dnc_resolve(dnc, "www.microsoft.com", MIO_DNS_RRT_CNAME, MIO_SVC_DNC_RESOLVE_FLAG_COOKIE, on_dnc_resolve, 0))
 {
 	printf ("resolve attempt failure ---> www.microsoft.com\n");
 }

mio/lib/dns-cli.c

@@ -862,7 +862,7 @@ static void on_dnc_resolve (mio_svc_dnc_t* dnc, mio_dns_msg_t* reqmsg, mio_errnu
 	if (!(reqmsgxtn->flags & MIO_SVC_DNC_RESOLVE_FLAG_BRIEF))
 	{
 		/* the full reply packet is requested. no transformation is required */
-		if (reqmsgxtn->on_resolve) reqmsgxtn->on_resolve(dnc, reqmsg, status, data, dlen);
+		if (reqmsgxtn->on_resolve) reqmsgxtn->on_resolve (dnc, reqmsg, status, data, dlen);
 		return;
 	}
 
@@ -965,7 +965,7 @@ mio_dns_msg_t* mio_svc_dnc_resolve (mio_svc_dnc_t* dnc, const mio_bch_t* qname,
 		MIO_DNS_RCODE_NOERROR /* rcode */
 	};
 
-	static mio_dns_bedns_t qedns =
+	mio_dns_bedns_t qedns =
 	{
 		4096, /* uplen */
 
@@ -976,6 +976,8 @@ mio_dns_msg_t* mio_svc_dnc_resolve (mio_svc_dnc_t* dnc, const mio_bch_t* qname,
 		MIO_NULL
 	};
 
+	mio_dns_beopt_t beopt_cookie;
+
 	mio_dns_bqr_t qr;
 	mio_dns_msg_t* reqmsg;
 	dnc_dns_msg_resolve_xtn_t* resolxtn;
@@ -984,11 +986,49 @@ mio_dns_msg_t* mio_svc_dnc_resolve (mio_svc_dnc_t* dnc, const mio_bch_t* qname,
 	qr.qtype = qtype;
 	qr.qclass = MIO_DNS_RRC_IN;
 
+	if (resolve_flags & MIO_SVC_DNC_RESOLVE_FLAG_COOKIE)
+	{
+		static mio_uint8_t dummy[48];
+		beopt_cookie.code = MIO_DNS_EOPT_COOKIE;
+		beopt_cookie.dlen = MIO_COUNTOF(dummy);
+		beopt_cookie.dptr = dummy;
+
+		qedns.beonum = 1;
+		qedns.beoptr = &beopt_cookie;
+	}
+
 	reqmsg = make_dns_msg(dnc, &qhdr, &qr, 1, MIO_NULL, 0, &qedns, on_dnc_resolve, MIO_SIZEOF(*resolxtn) + xtnsize);
 	if (reqmsg)
 	{
 		int send_flags;
 
+		if (resolve_flags & MIO_SVC_DNC_RESOLVE_FLAG_COOKIE)
+		{
+			/* ASSUMPTIONS:
+			 *  the eopt entries are at the back of the packet.
+			 *  only 1 eopt entry(MIO_DNS_EOPT_COOKIE) has been added. 
+			 * 
+			 * manipulate the data length of the EDNS0 RR and COOKIE option 
+			 * as if the server cookie data has not been added.
+			 */
+			mio_dns_rrtr_t* edns_rrtr;
+			mio_dns_eopt_t* eopt;
+
+/* TODO: generate the client cookie and copy it */
+/* if the server cookie is available, copy it to the packet. but the server cookike may still be shorter than 40. so some manipulation is still needed
+ * if not, manipualte the length like below */
+			edns_rrtr = (mio_dns_rrtr_t*)((mio_uint8_t*)mio_dns_msg_to_pkt(reqmsg) + reqmsg->ednsrrtroff);
+			reqmsg->pktlen -= 40; /* maximum server cookie space */
+
+			MIO_ASSERT (dnc->mio, edns_rrtr->rrtype == MIO_CONST_HTON16(MIO_DNS_RRT_OPT));
+			MIO_ASSERT (dnc->mio, edns_rrtr->dlen == MIO_CONST_HTON16(52));
+
+			edns_rrtr->dlen = MIO_CONST_HTON16(12);
+			eopt = (mio_dns_eopt_t*)(edns_rrtr + 1);
+			MIO_ASSERT (dnc->mio, eopt->dlen == MIO_CONST_HTON16(48));
+			eopt->dlen = MIO_CONST_HTON16(8);
+		}
+
 		resolxtn = dnc_dns_msg_resolve_getxtn(reqmsg);
 		resolxtn->on_resolve = on_resolve;
 		resolxtn->qtype = qtype;

mio/lib/dns.c

@@ -746,7 +746,7 @@ mio_dns_msg_t* mio_dns_make_msg (mio_t* mio, mio_dns_bhdr_t* bhdr, mio_dns_bqr_t
 
 /* TODO: msg buffer reuse */
 	msg = mio_callocmem(mio, msgbufsz);
-	if (!msg) return MIO_NULL;
+	if (MIO_UNLIKELY(!msg)) return MIO_NULL;
 
 	msg->msglen = msgbufsz; /* record the instance size */
 	msg->pktalilen = MIO_ALIGN_POW2(pktlen, MIO_SIZEOF_VOID_P);
@@ -812,6 +812,7 @@ mio_dns_msg_t* mio_dns_make_msg (mio_t* mio, mio_dns_bhdr_t* bhdr, mio_dns_bqr_t
 
 		beopt = edns->beoptr;
 		eopt = (mio_dns_eopt_t*)dn;
+		msg->ednsrrtroff = (mio_uint8_t*)rrtr - (mio_uint8_t*)pkt;
 
 		for (i = 0; i < edns->beonum; i++)
 		{

mio/lib/mio-dns.h

@@ -162,6 +162,7 @@ typedef struct mio_dns_msg_t mio_dns_msg_t;
 struct mio_dns_msg_t
 {
 	mio_oow_t      msglen;
+	mio_oow_t      ednsrrtroff; /* offset to trailing data after the name in the dns0 RR*/
 	mio_oow_t      pktlen;
 	mio_oow_t      pktalilen;
 };
@@ -405,8 +406,9 @@ enum mio_svc_dnc_resolve_flag_t
 
 	/* the following flag bits are resolver specific. it must not overlap with send flag bits */
 	MIO_SVC_DNC_RESOLVE_FLAG_BRIEF      = (1 << 8),
+	MIO_SVC_DNC_RESOLVE_FLAG_COOKIE     = (1 << 9),
 
-	MIO_SVC_DNC_RESOLVE_FLAG_ALL = (MIO_SVC_DNC_RESOLVE_FLAG_PREFER_TCP | MIO_SVC_DNC_RESOLVE_FLAG_TCP_IF_TC | MIO_SVC_DNC_RESOLVE_FLAG_BRIEF)
+	MIO_SVC_DNC_RESOLVE_FLAG_ALL = (MIO_SVC_DNC_RESOLVE_FLAG_PREFER_TCP | MIO_SVC_DNC_RESOLVE_FLAG_TCP_IF_TC | MIO_SVC_DNC_RESOLVE_FLAG_BRIEF | MIO_SVC_DNC_RESOLVE_FLAG_COOKIE)
 };
 typedef enum mio_svc_dnc_resolve_flag_t  mio_svc_dnc_resolve_flag_t;