: Finishing Ack Vector patch set

@@ -475,6 +475,7 @@ struct dccp_ackvec;
  * @dccps_hc_rx_insert_options - receiver wants to add options when acking
  * @dccps_hc_tx_insert_options - sender wants to add options when sending
  * @dccps_server_timewait - server holds timewait state on close (RFC 4340, 8.3)
+ * @dccps_sync_scheduled - flag which signals "send out-of-band message soon"
  * @dccps_xmit_timer - timer for when CCID is not ready to send
  * @dccps_syn_rtt - RTT sample from Request/Response exchange (in usecs)
  */

@@ -515,6 +516,7 @@ struct dccp_sock {
 	__u8				dccps_hc_rx_insert_options:1;
 	__u8				dccps_hc_tx_insert_options:1;
 	__u8				dccps_server_timewait:1;
+	__u8				dccps_sync_scheduled:1;
 	struct timer_list		dccps_xmit_timer;
 };
 

@@ -426,7 +426,9 @@ static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
 
 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 {
-	struct dccp_ackvec *av = dccp_sk(sk)->dccps_hc_rx_ackvec;
+	struct dccp_sock *dp = dccp_sk(sk);
+	struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
+	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 	const u16 buflen = dccp_ackvec_buflen(av);
 	/* Figure out how many options do we need to represent the ackvec */
 	const u16 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN);

@@ -435,16 +437,24 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 	const unsigned char *tail, *from;
 	unsigned char *to;
 
-	if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
-		/*
-		 * FIXME: when running out of option space while piggybacking on
-		 * DataAck, return 0 here and schedule a separate Ack instead.
-		 */
+	if (dcb->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
 		DCCP_WARN("Lacking space for %u bytes on %s packet\n", len,
-			  dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type));
+			  dccp_packet_name(dcb->dccpd_type));
 		return -1;
 	}
-	DCCP_SKB_CB(skb)->dccpd_opt_len += len;
+	/*
+	 * Since Ack Vectors are variable-length, we can not always predict
+	 * their size. To catch exception cases where the space is running out
+	 * on the skb, a separate Sync is scheduled to carry the Ack Vector.
+	 */
+	if (dcb->dccpd_opt_len + skb->len + len > dp->dccps_mss_cache) {
+		DCCP_WARN("No space left for Ack Vector (%u) on skb (%u+%u), "
+			  "MPS=%u => reduce payload size?\n", len, skb->len,
+			  dcb->dccpd_opt_len, dp->dccps_mss_cache);
+		dp->dccps_sync_scheduled = 1;
+		return 0;
+	}
+	dcb->dccpd_opt_len += len;
 
 	to   = skb_push(skb, len);
 	len  = buflen;

@@ -485,7 +495,7 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 	/*
 	 * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
 	 */
-	if (dccp_ackvec_update_records(av, DCCP_SKB_CB(skb)->dccpd_seq, nonce))
+	if (dccp_ackvec_update_records(av, dcb->dccpd_seq, nonce))
 		return -ENOBUFS;
 	return 0;
 }

@@ -282,6 +282,8 @@ void dccp_write_xmit(struct sock *sk, int block)
 			if (err)
 				DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
 					 err);
+			if (dp->dccps_sync_scheduled)
+				dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 		} else {
 			dccp_pr_debug("packet discarded due to err=%d\n", err);
 			kfree_skb(skb);

@@ -574,6 +576,12 @@ void dccp_send_sync(struct sock *sk, const u64 ackno,
 	DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 	DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
 
+	/*
+	 * Clear the flag in case the Sync was scheduled for out-of-band data,
+	 * such as carrying a long Ack Vector.
+	 */
+	dccp_sk(sk)->dccps_sync_scheduled = 0;
+
 	dccp_transmit_skb(sk, skb);
 }
 

@@ -112,4 +112,23 @@ static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
 {
 	return av->av_overflow = 0 && av->av_buf_head = av->av_buf_tail;
 }
+
+/**
+ * struct dccp_ackvec_parsed  -  Record offsets of Ack Vectors in skb
+ * @vec:	start of vector (offset into skb)
+ * @len:	length of @vec
+ * @nonce:	whether @vec had an ECN nonce of 0 or 1
+ * @node:	FIFO - arranged in descending order of ack_ackno
+ * This structure is used by CCIDs to access Ack Vectors in a received skb.
+ */
+struct dccp_ackvec_parsed {
+	u8		 *vec,
+			 len,
+			 nonce:1;
+	struct list_head node;
+};
+
+extern int dccp_ackvec_parsed_add(struct list_head *head,
+				  u8 *vec, u8 len, u8 nonce);
+extern void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
 #endif /* _ACKVEC_H */

@@ -135,13 +135,6 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
 			if (rc)
 				goto out_invalid_option;
 			break;
-		case DCCPO_ACK_VECTOR_0:
-		case DCCPO_ACK_VECTOR_1:
-			if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
-				break;
-			dccp_pr_debug("%s Ack Vector (len=%u)\n", dccp_role(sk),
-				      len);
-			break;
 		case DCCPO_TIMESTAMP:
 			if (len != 4)
 				goto out_invalid_option;

@@ -229,6 +222,16 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
 						     value) != 0)
 				goto out_invalid_option;
 			break;
+		case DCCPO_ACK_VECTOR_0:
+		case DCCPO_ACK_VECTOR_1:
+			if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
+				break;
+			/*
+			 * Ack vectors are processed by the TX CCID if it is
+			 * interested. The RX CCID need not parse Ack Vectors,
+			 * since it is only interested in clearing old state.
+			 * Fall through.
+			 */
 		case DCCPO_MIN_TX_CCID_SPECIFIC ... DCCPO_MAX_TX_CCID_SPECIFIC:
 			if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
 						     opt, len, value - options,

@@ -345,6 +345,34 @@ free_records:
 	}
 }
 
+/*
+ *	Routines to keep track of Ack Vectors received in an skb
+ */
+int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce)
+{
+	struct dccp_ackvec_parsed *new = kmalloc(sizeof(*new), GFP_ATOMIC);
+
+	if (new = NULL)
+		return -ENOBUFS;
+	new->vec   = vec;
+	new->len   = len;
+	new->nonce = nonce;
+
+	list_add_tail(&new->node, head);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_add);
+
+void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks)
+{
+	struct dccp_ackvec_parsed *cur, *next;
+
+	list_for_each_entry_safe(cur, next, parsed_chunks, node)
+		kfree(cur);
+	INIT_LIST_HEAD(parsed_chunks);
+}
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_cleanup);
+
 int __init dccp_ackvec_init(void)
 {
 	dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",

@@ -47,6 +47,7 @@ struct ccid2_seq {
  * @ccid2hctx_lastrtt -time RTT was last measured
  * @ccid2hctx_rpseq - last consecutive seqno
  * @ccid2hctx_rpdupack - dupacks since rpseq
+ * @ccid2hctx_parsed_ackvecs: list of Ack Vectors received on current skb
 */
 struct ccid2_hc_tx_sock {
 	u32			ccid2hctx_cwnd;

@@ -66,6 +67,7 @@ struct ccid2_hc_tx_sock {
 	int			ccid2hctx_rpdupack;
 	unsigned long		ccid2hctx_last_cong;
 	u64			ccid2hctx_high_ack;
+	struct list_head	ccid2hctx_parsed_ackvecs;
 };
 
 struct ccid2_hc_rx_sock {

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