1 files changed, 237 insertions, 316 deletions

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 7e746c4c168..90c74b4adb7 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -113,13 +113,8 @@ int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	/* OK, now commit destination to socket.  */
 	sk_setup_caps(sk, &rt->u.dst);
 
-	dp->dccps_gar =
-		dp->dccps_iss = secure_dccp_sequence_number(inet->saddr,
-							    inet->daddr,
-							    inet->sport,
-							    usin->sin_port);
-	dccp_update_gss(sk, dp->dccps_iss);
-
+	dp->dccps_iss = secure_dccp_sequence_number(inet->saddr, inet->daddr,
+						    inet->sport, inet->dport);
 	inet->id = dp->dccps_iss ^ jiffies;
 
 	err = dccp_connect(sk);
@@ -162,7 +157,7 @@ static inline void dccp_do_pmtu_discovery(struct sock *sk,
 	/* We don't check in the destentry if pmtu discovery is forbidden
 	 * on this route. We just assume that no packet_to_big packets
 	 * are send back when pmtu discovery is not active.
-     	 * There is a small race when the user changes this flag in the
+ 	 * There is a small race when the user changes this flag in the
 	 * route, but I think that's acceptable.
 	 */
 	if ((dst = __sk_dst_check(sk, 0)) == NULL)
@@ -183,7 +178,7 @@ static inline void dccp_do_pmtu_discovery(struct sock *sk,
 		dccp_sync_mss(sk, mtu);
 
 		/*
-		 * From: draft-ietf-dccp-spec-11.txt
+		 * From RFC 4340, sec. 14.1:
 		 *
 		 *	DCCP-Sync packets are the best choice for upward
 		 *	probing, since DCCP-Sync probes do not risk application
@@ -193,86 +188,6 @@ static inline void dccp_do_pmtu_discovery(struct sock *sk,
 	} /* else let the usual retransmit timer handle it */
 }
 
-static void dccp_v4_reqsk_send_ack(struct sk_buff *rxskb,
-				   struct request_sock *req)
-{
-	int err;
-	struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
-	const u32 dccp_hdr_ack_len = sizeof(struct dccp_hdr) +
-				     sizeof(struct dccp_hdr_ext) +
-				     sizeof(struct dccp_hdr_ack_bits);
-	struct sk_buff *skb;
-
-	if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
-		return;
-
-	skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header, GFP_ATOMIC);
-	if (skb == NULL)
-		return;
-
-	/* Reserve space for headers. */
-	skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
-
-	skb->dst = dst_clone(rxskb->dst);
-
-	skb->h.raw = skb_push(skb, dccp_hdr_ack_len);
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_hdr_ack_len);
-
-	/* Build DCCP header and checksum it. */
-	dh->dccph_type	   = DCCP_PKT_ACK;
-	dh->dccph_sport	   = rxdh->dccph_dport;
-	dh->dccph_dport	   = rxdh->dccph_sport;
-	dh->dccph_doff	   = dccp_hdr_ack_len / 4;
-	dh->dccph_x	   = 1;
-
-	dccp_hdr_set_seq(dh, DCCP_SKB_CB(rxskb)->dccpd_ack_seq);
-	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb),
-			 DCCP_SKB_CB(rxskb)->dccpd_seq);
-
-	bh_lock_sock(dccp_v4_ctl_socket->sk);
-	err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
-				    rxskb->nh.iph->daddr,
-				    rxskb->nh.iph->saddr, NULL);
-	bh_unlock_sock(dccp_v4_ctl_socket->sk);
-
-	if (err == NET_XMIT_CN || err == 0) {
-		DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
-		DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
-	}
-}
-
-static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
-				 struct dst_entry *dst)
-{
-	int err = -1;
-	struct sk_buff *skb;
-
-	/* First, grab a route. */
-	
-	if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
-		goto out;
-
-	skb = dccp_make_response(sk, dst, req);
-	if (skb != NULL) {
-		const struct inet_request_sock *ireq = inet_rsk(req);
-		struct dccp_hdr *dh = dccp_hdr(skb);
-
-		dh->dccph_checksum = dccp_v4_checksum(skb, ireq->loc_addr,
-						      ireq->rmt_addr);
-		memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
-		err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
-					    ireq->rmt_addr,
-					    ireq->opt);
-		if (err == NET_XMIT_CN)
-			err = 0;
-	}
-
-out:
-	dst_release(dst);
-	return err;
-}
-
 /*
  * This routine is called by the ICMP module when it gets some sort of error
  * condition. If err < 0 then the socket should be closed and the error
@@ -329,7 +244,7 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
 	seq = dccp_hdr_seq(skb);
 	if (sk->sk_state != DCCP_LISTEN &&
 	    !between48(seq, dp->dccps_swl, dp->dccps_swh)) {
-		NET_INC_STATS(LINUX_MIB_OUTOFWINDOWICMPS);
+		NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
 		goto out;
 	}
 
@@ -429,19 +344,24 @@ out:
 	sock_put(sk);
 }
 
-/* This routine computes an IPv4 DCCP checksum. */
-void dccp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
+static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
+				      __be32 src, __be32 dst)
+{
+	return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
+}
+
+void dccp_v4_send_check(struct sock *sk, int unused, struct sk_buff *skb)
 {
 	const struct inet_sock *inet = inet_sk(sk);
 	struct dccp_hdr *dh = dccp_hdr(skb);
 
-	dh->dccph_checksum = dccp_v4_checksum(skb, inet->saddr, inet->daddr);
+	dccp_csum_outgoing(skb);
+	dh->dccph_checksum = dccp_v4_csum_finish(skb, inet->saddr, inet->daddr);
 }
 
 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
 
-static inline u64 dccp_v4_init_sequence(const struct sock *sk,
-					const struct sk_buff *skb)
+static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
 {
 	return secure_dccp_sequence_number(skb->nh.iph->daddr,
 					   skb->nh.iph->saddr,
@@ -449,93 +369,6 @@ static inline u64 dccp_v4_init_sequence(const struct sock *sk,
 					   dccp_hdr(skb)->dccph_sport);
 }
 
-int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
-{
-	struct inet_request_sock *ireq;
-	struct dccp_sock dp;
-	struct request_sock *req;
-	struct dccp_request_sock *dreq;
-	const __be32 saddr = skb->nh.iph->saddr;
-	const __be32 daddr = skb->nh.iph->daddr;
- 	const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
-	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
-	__u8 reset_code = DCCP_RESET_CODE_TOO_BUSY;
-
-	/* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
-	if (((struct rtable *)skb->dst)->rt_flags &
-	    (RTCF_BROADCAST | RTCF_MULTICAST)) {
-		reset_code = DCCP_RESET_CODE_NO_CONNECTION;
-		goto drop;
-	}
-
-	if (dccp_bad_service_code(sk, service)) {
-		reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
-		goto drop;
- 	}
-	/*
-	 * TW buckets are converted to open requests without
-	 * limitations, they conserve resources and peer is
-	 * evidently real one.
-	 */
-	if (inet_csk_reqsk_queue_is_full(sk))
-		goto drop;
-
-	/*
-	 * Accept backlog is full. If we have already queued enough
-	 * of warm entries in syn queue, drop request. It is better than
-	 * clogging syn queue with openreqs with exponentially increasing
-	 * timeout.
-	 */
-	if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
-		goto drop;
-
-	req = reqsk_alloc(sk->sk_prot->rsk_prot);
-	if (req == NULL)
-		goto drop;
-
-	if (dccp_parse_options(sk, skb))
-		goto drop_and_free;
-
-	dccp_openreq_init(req, &dp, skb);
-
-	if (security_inet_conn_request(sk, skb, req))
-		goto drop_and_free;
-
-	ireq = inet_rsk(req);
-	ireq->loc_addr = daddr;
-	ireq->rmt_addr = saddr;
-	req->rcv_wnd	= dccp_feat_default_sequence_window;
-	ireq->opt	= NULL;
-
-	/* 
-	 * Step 3: Process LISTEN state
-	 *
-	 * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
-	 *
-	 * In fact we defer setting S.GSR, S.SWL, S.SWH to
-	 * dccp_create_openreq_child.
-	 */
-	dreq = dccp_rsk(req);
-	dreq->dreq_isr	   = dcb->dccpd_seq;
-	dreq->dreq_iss	   = dccp_v4_init_sequence(sk, skb);
-	dreq->dreq_service = service;
-
-	if (dccp_v4_send_response(sk, req, NULL))
-		goto drop_and_free;
-
-	inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
-	return 0;
-
-drop_and_free:
-	reqsk_free(req);
-drop:
-	DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
-	dcb->dccpd_reset_code = reset_code;
-	return -1;
-}
-
-EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
-
 /*
  * The three way handshake has completed - we got a valid ACK or DATAACK -
  * now create the new socket.
@@ -621,47 +454,6 @@ static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
 	return sk;
 }
 
-int dccp_v4_checksum(const struct sk_buff *skb, const __be32 saddr,
-		     const __be32 daddr)
-{
-	const struct dccp_hdr* dh = dccp_hdr(skb);
-	int checksum_len;
-	u32 tmp;
-
-	if (dh->dccph_cscov == 0)
-		checksum_len = skb->len;
-	else {
-		checksum_len = (dh->dccph_cscov + dh->dccph_x) * sizeof(u32);
-		checksum_len = checksum_len < skb->len ? checksum_len :
-							 skb->len;
-	}
-
-	tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
-	return csum_tcpudp_magic(saddr, daddr, checksum_len,
-				 IPPROTO_DCCP, tmp);
-}
-
-EXPORT_SYMBOL_GPL(dccp_v4_checksum);
-
-static int dccp_v4_verify_checksum(struct sk_buff *skb,
-				   const __be32 saddr, const __be32 daddr)
-{
-	struct dccp_hdr *dh = dccp_hdr(skb);
-	int checksum_len;
-	u32 tmp;
-
-	if (dh->dccph_cscov == 0)
-		checksum_len = skb->len;
-	else {
-		checksum_len = (dh->dccph_cscov + dh->dccph_x) * sizeof(u32);
-		checksum_len = checksum_len < skb->len ? checksum_len :
-							 skb->len;
-	}
-	tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
-	return csum_tcpudp_magic(saddr, daddr, checksum_len,
-				 IPPROTO_DCCP, tmp) == 0 ? 0 : -1;
-}
-
 static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
 					   struct sk_buff *skb)
 {
@@ -675,7 +467,7 @@ static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
 			    .uli_u = { .ports =
 				       { .sport = dccp_hdr(skb)->dccph_dport,
 					 .dport = dccp_hdr(skb)->dccph_sport }
-			   	     }
+				     }
 			  };
 
 	security_skb_classify_flow(skb, &fl);
@@ -687,7 +479,37 @@ static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
 	return &rt->u.dst;
 }
 
-static void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
+static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
+				 struct dst_entry *dst)
+{
+	int err = -1;
+	struct sk_buff *skb;
+
+	/* First, grab a route. */
+	
+	if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
+		goto out;
+
+	skb = dccp_make_response(sk, dst, req);
+	if (skb != NULL) {
+		const struct inet_request_sock *ireq = inet_rsk(req);
+		struct dccp_hdr *dh = dccp_hdr(skb);
+
+		dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
+							      ireq->rmt_addr);
+		memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
+		err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
+					    ireq->rmt_addr,
+					    ireq->opt);
+		err = net_xmit_eval(err);
+	}
+
+out:
+	dst_release(dst);
+	return err;
+}
+
+static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 {
 	int err;
 	struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
@@ -696,7 +518,7 @@ static void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
 				       sizeof(struct dccp_hdr_reset);
 	struct sk_buff *skb;
 	struct dst_entry *dst;
-	u64 seqno;
+	u64 seqno = 0;
 
 	/* Never send a reset in response to a reset. */
 	if (rxdh->dccph_type == DCCP_PKT_RESET)
@@ -718,9 +540,7 @@ static void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
 	skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
 	skb->dst = dst_clone(dst);
 
-	skb->h.raw = skb_push(skb, dccp_hdr_reset_len);
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_hdr_reset_len);
+	dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 
 	/* Build DCCP header and checksum it. */
 	dh->dccph_type	   = DCCP_PKT_RESET;
@@ -731,17 +551,16 @@ static void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
 	dccp_hdr_reset(skb)->dccph_reset_code =
 				DCCP_SKB_CB(rxskb)->dccpd_reset_code;
 
-	/* See "8.3.1. Abnormal Termination" in draft-ietf-dccp-spec-11 */
-	seqno = 0;
+	/* See "8.3.1. Abnormal Termination" in RFC 4340 */
 	if (DCCP_SKB_CB(rxskb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 		dccp_set_seqno(&seqno, DCCP_SKB_CB(rxskb)->dccpd_ack_seq + 1);
 
 	dccp_hdr_set_seq(dh, seqno);
-	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb),
-			 DCCP_SKB_CB(rxskb)->dccpd_seq);
+	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), DCCP_SKB_CB(rxskb)->dccpd_seq);
 
-	dh->dccph_checksum = dccp_v4_checksum(skb, rxskb->nh.iph->saddr,
-					      rxskb->nh.iph->daddr);
+	dccp_csum_outgoing(skb);
+	dh->dccph_checksum = dccp_v4_csum_finish(skb, rxskb->nh.iph->saddr,
+						      rxskb->nh.iph->daddr);
 
 	bh_lock_sock(dccp_v4_ctl_socket->sk);
 	err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
@@ -749,7 +568,7 @@ static void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
 				    rxskb->nh.iph->saddr, NULL);
 	bh_unlock_sock(dccp_v4_ctl_socket->sk);
 
-	if (err == NET_XMIT_CN || err == 0) {
+	if (net_xmit_eval(err) == 0) {
 		DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
 		DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
 	}
@@ -757,6 +576,103 @@ out:
 	 dst_release(dst);
 }
 
+static void dccp_v4_reqsk_destructor(struct request_sock *req)
+{
+	kfree(inet_rsk(req)->opt);
+}
+
+static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
+	.family		= PF_INET,
+	.obj_size	= sizeof(struct dccp_request_sock),
+	.rtx_syn_ack	= dccp_v4_send_response,
+	.send_ack	= dccp_reqsk_send_ack,
+	.destructor	= dccp_v4_reqsk_destructor,
+	.send_reset	= dccp_v4_ctl_send_reset,
+};
+
+int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
+{
+	struct inet_request_sock *ireq;
+	struct request_sock *req;
+	struct dccp_request_sock *dreq;
+	const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
+	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
+	__u8 reset_code = DCCP_RESET_CODE_TOO_BUSY;
+
+	/* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
+	if (((struct rtable *)skb->dst)->rt_flags &
+	    (RTCF_BROADCAST | RTCF_MULTICAST)) {
+		reset_code = DCCP_RESET_CODE_NO_CONNECTION;
+		goto drop;
+	}
+
+	if (dccp_bad_service_code(sk, service)) {
+		reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
+		goto drop;
+	}
+	/*
+	 * TW buckets are converted to open requests without
+	 * limitations, they conserve resources and peer is
+	 * evidently real one.
+	 */
+	if (inet_csk_reqsk_queue_is_full(sk))
+		goto drop;
+
+	/*
+	 * Accept backlog is full. If we have already queued enough
+	 * of warm entries in syn queue, drop request. It is better than
+	 * clogging syn queue with openreqs with exponentially increasing
+	 * timeout.
+	 */
+	if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
+		goto drop;
+
+	req = reqsk_alloc(&dccp_request_sock_ops);
+	if (req == NULL)
+		goto drop;
+
+	if (dccp_parse_options(sk, skb))
+		goto drop_and_free;
+
+	dccp_reqsk_init(req, skb);
+
+	if (security_inet_conn_request(sk, skb, req))
+		goto drop_and_free;
+
+	ireq = inet_rsk(req);
+	ireq->loc_addr = skb->nh.iph->daddr;
+	ireq->rmt_addr = skb->nh.iph->saddr;
+	ireq->opt	= NULL;
+
+	/*
+	 * Step 3: Process LISTEN state
+	 *
+	 * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
+	 *
+	 * In fact we defer setting S.GSR, S.SWL, S.SWH to
+	 * dccp_create_openreq_child.
+	 */
+	dreq = dccp_rsk(req);
+	dreq->dreq_isr	   = dcb->dccpd_seq;
+	dreq->dreq_iss	   = dccp_v4_init_sequence(skb);
+	dreq->dreq_service = service;
+
+	if (dccp_v4_send_response(sk, req, NULL))
+		goto drop_and_free;
+
+	inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
+	return 0;
+
+drop_and_free:
+	reqsk_free(req);
+drop:
+	DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
+	dcb->dccpd_reset_code = reset_code;
+	return -1;
+}
+
+EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
+
 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 {
 	struct dccp_hdr *dh = dccp_hdr(skb);
@@ -769,24 +685,23 @@ int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 
 	/*
 	 *  Step 3: Process LISTEN state
-	 *     If S.state == LISTEN,
-	 *	  If P.type == Request or P contains a valid Init Cookie
-	 *	  	option,
-	 *	     * Must scan the packet's options to check for an Init
-	 *		Cookie.  Only the Init Cookie is processed here,
-	 *		however; other options are processed in Step 8.  This
-	 *		scan need only be performed if the endpoint uses Init
-	 *		Cookies *
-	 *	     * Generate a new socket and switch to that socket *
-	 *	     Set S := new socket for this port pair
-	 *	     S.state = RESPOND
-	 *	     Choose S.ISS (initial seqno) or set from Init Cookie
-	 *	     Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
-	 *	     Continue with S.state == RESPOND
-	 *	     * A Response packet will be generated in Step 11 *
-	 *	  Otherwise,
-	 *	     Generate Reset(No Connection) unless P.type == Reset
-	 *	     Drop packet and return
+	 *	 If P.type == Request or P contains a valid Init Cookie option,
+	 *	      (* Must scan the packet's options to check for Init
+	 *		 Cookies.  Only Init Cookies are processed here,
+	 *		 however; other options are processed in Step 8.  This
+	 *		 scan need only be performed if the endpoint uses Init
+	 *		 Cookies *)
+	 *	      (* Generate a new socket and switch to that socket *)
+	 *	      Set S := new socket for this port pair
+	 *	      S.state = RESPOND
+	 *	      Choose S.ISS (initial seqno) or set from Init Cookies
+	 *	      Initialize S.GAR := S.ISS
+	 *	      Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
+	 *	      Continue with S.state == RESPOND
+	 *	      (* A Response packet will be generated in Step 11 *)
+	 *	 Otherwise,
+	 *	      Generate Reset(No Connection) unless P.type == Reset
+	 *	      Drop packet and return
 	 *
 	 * NOTE: the check for the packet types is done in
 	 *	 dccp_rcv_state_process
@@ -809,7 +724,7 @@ int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 	return 0;
 
 reset:
-	dccp_v4_ctl_send_reset(skb);
+	dccp_v4_ctl_send_reset(sk, skb);
 discard:
 	kfree_skb(skb);
 	return 0;
@@ -817,60 +732,74 @@ discard:
 
 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
 
+/**
+ *	dccp_invalid_packet  -  check for malformed packets
+ *	Implements RFC 4340, 8.5:  Step 1: Check header basics
+ *	Packets that fail these checks are ignored and do not receive Resets.
+ */
 int dccp_invalid_packet(struct sk_buff *skb)
 {
 	const struct dccp_hdr *dh;
+	unsigned int cscov;
 
 	if (skb->pkt_type != PACKET_HOST)
 		return 1;
 
+	/* If the packet is shorter than 12 bytes, drop packet and return */
 	if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
-		LIMIT_NETDEBUG(KERN_WARNING "DCCP: pskb_may_pull failed\n");
+		DCCP_WARN("pskb_may_pull failed\n");
 		return 1;
 	}
 
 	dh = dccp_hdr(skb);
 
-	/* If the packet type is not understood, drop packet and return */
+	/* If P.type is not understood, drop packet and return */
 	if (dh->dccph_type >= DCCP_PKT_INVALID) {
-		LIMIT_NETDEBUG(KERN_WARNING "DCCP: invalid packet type\n");
+		DCCP_WARN("invalid packet type\n");
 		return 1;
 	}
 
 	/*
-	 * If P.Data Offset is too small for packet type, or too large for
-	 * packet, drop packet and return
+	 * If P.Data Offset is too small for packet type, drop packet and return
 	 */
 	if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
-		LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.Data Offset(%u) "
-					    "too small 1\n",
-			       dh->dccph_doff);
+		DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
 		return 1;
 	}
-
+	/*
+	 * If P.Data Offset is too too large for packet, drop packet and return
+	 */
 	if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
-		LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.Data Offset(%u) "
-					    "too small 2\n",
-			       dh->dccph_doff);
+		DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
 		return 1;
 	}
 
-	dh = dccp_hdr(skb);
-
 	/*
 	 * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
 	 * has short sequence numbers), drop packet and return
 	 */
-	if (dh->dccph_x == 0 &&
-	    dh->dccph_type != DCCP_PKT_DATA &&
-	    dh->dccph_type != DCCP_PKT_ACK &&
-	    dh->dccph_type != DCCP_PKT_DATAACK) {
-		LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.type (%s) not Data, Ack "
-					    "nor DataAck and P.X == 0\n",
-			       dccp_packet_name(dh->dccph_type));
+	if (dh->dccph_type >= DCCP_PKT_DATA    &&
+	    dh->dccph_type <= DCCP_PKT_DATAACK && dh->dccph_x == 0)  {
+		DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
+			  dccp_packet_name(dh->dccph_type));
 		return 1;
 	}
 
+	/*
+	 * If P.CsCov is too large for the packet size, drop packet and return.
+	 * This must come _before_ checksumming (not as RFC 4340 suggests).
+	 */
+	cscov = dccp_csum_coverage(skb);
+	if (cscov > skb->len) {
+		DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
+			  dh->dccph_cscov, skb->len);
+		return 1;
+	}
+
+	/* If header checksum is incorrect, drop packet and return.
+	 * (This step is completed in the AF-dependent functions.) */
+	skb->csum = skb_checksum(skb, 0, cscov, 0);
+
 	return 0;
 }
 
@@ -881,17 +810,16 @@ static int dccp_v4_rcv(struct sk_buff *skb)
 {
 	const struct dccp_hdr *dh;
 	struct sock *sk;
+	int min_cov;
 
-	/* Step 1: Check header basics: */
+	/* Step 1: Check header basics */
 
 	if (dccp_invalid_packet(skb))
 		goto discard_it;
 
-	/* If the header checksum is incorrect, drop packet and return */
-	if (dccp_v4_verify_checksum(skb, skb->nh.iph->saddr,
-				    skb->nh.iph->daddr) < 0) {
-		LIMIT_NETDEBUG(KERN_WARNING "%s: incorrect header checksum\n",
-			       __FUNCTION__);
+	/* Step 1: If header checksum is incorrect, drop packet and return */
+	if (dccp_v4_csum_finish(skb, skb->nh.iph->saddr, skb->nh.iph->daddr)) {
+		DCCP_WARN("dropped packet with invalid checksum\n");
 		goto discard_it;
 	}
 
@@ -913,23 +841,20 @@ static int dccp_v4_rcv(struct sk_buff *skb)
 		dccp_pr_debug_cat("\n");
 	} else {
 		DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
-		dccp_pr_debug_cat(", ack=%llu\n",
-				  (unsigned long long)
+		dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
 				  DCCP_SKB_CB(skb)->dccpd_ack_seq);
 	}
 
 	/* Step 2:
-	 * 	Look up flow ID in table and get corresponding socket */
+	 *	Look up flow ID in table and get corresponding socket */
 	sk = __inet_lookup(&dccp_hashinfo,
 			   skb->nh.iph->saddr, dh->dccph_sport,
 			   skb->nh.iph->daddr, dh->dccph_dport,
 			   inet_iif(skb));
 
-	/* 
+	/*
 	 * Step 2:
-	 * 	If no socket ...
-	 *		Generate Reset(No Connection) unless P.type == Reset
-	 *		Drop packet and return
+	 *	If no socket ...
 	 */
 	if (sk == NULL) {
 		dccp_pr_debug("failed to look up flow ID in table and "
@@ -937,51 +862,61 @@ static int dccp_v4_rcv(struct sk_buff *skb)
 		goto no_dccp_socket;
 	}
 
-	/* 
+	/*
 	 * Step 2:
-	 * 	... or S.state == TIMEWAIT,
+	 *	... or S.state == TIMEWAIT,
 	 *		Generate Reset(No Connection) unless P.type == Reset
 	 *		Drop packet and return
 	 */
-	       
 	if (sk->sk_state == DCCP_TIME_WAIT) {
-		dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: "
-			      "do_time_wait\n");
-                goto do_time_wait;
+		dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
+		inet_twsk_put(inet_twsk(sk));
+		goto no_dccp_socket;
+	}
+
+	/*
+	 * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
+	 *	o if MinCsCov = 0, only packets with CsCov = 0 are accepted
+	 *	o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
+	 */
+	min_cov = dccp_sk(sk)->dccps_pcrlen;
+	if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
+		dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
+			      dh->dccph_cscov, min_cov);
+		/* FIXME: "Such packets SHOULD be reported using Data Dropped
+		 *         options (Section 11.7) with Drop Code 0, Protocol
+		 *         Constraints."                                     */
+		goto discard_and_relse;
 	}
 
 	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 		goto discard_and_relse;
 	nf_reset(skb);
 
-	return sk_receive_skb(sk, skb);
+	return sk_receive_skb(sk, skb, 1);
 
 no_dccp_socket:
 	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
 		goto discard_it;
 	/*
 	 * Step 2:
+	 *	If no socket ...
 	 *		Generate Reset(No Connection) unless P.type == Reset
 	 *		Drop packet and return
 	 */
 	if (dh->dccph_type != DCCP_PKT_RESET) {
 		DCCP_SKB_CB(skb)->dccpd_reset_code =
 					DCCP_RESET_CODE_NO_CONNECTION;
-		dccp_v4_ctl_send_reset(skb);
+		dccp_v4_ctl_send_reset(sk, skb);
 	}
 
 discard_it:
-	/* Discard frame. */
 	kfree_skb(skb);
 	return 0;
 
 discard_and_relse:
 	sock_put(sk);
 	goto discard_it;
-
-do_time_wait:
-	inet_twsk_put(inet_twsk(sk));
-	goto no_dccp_socket;
 }
 
 static struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
@@ -1015,20 +950,6 @@ static int dccp_v4_init_sock(struct sock *sk)
 	return err;
 }
 
-static void dccp_v4_reqsk_destructor(struct request_sock *req)
-{
-	kfree(inet_rsk(req)->opt);
-}
-
-static struct request_sock_ops dccp_request_sock_ops = {
-	.family		= PF_INET,
-	.obj_size	= sizeof(struct dccp_request_sock),
-	.rtx_syn_ack	= dccp_v4_send_response,
-	.send_ack	= dccp_v4_reqsk_send_ack,
-	.destructor	= dccp_v4_reqsk_destructor,
-	.send_reset	= dccp_v4_ctl_send_reset,
-};
-
 static struct timewait_sock_ops dccp_timewait_sock_ops = {
 	.twsk_obj_size	= sizeof(struct inet_timewait_sock),
 };