[DCCP] CCID2: Allocate seq records on demand

Allocate more sequence state on demand.  Each time a packet is sent
out by CCID2, a record of it needs to be kept.  This list of records
grows proportionally to cwnd.  Previously, the length of this list was
hardcored and therefore the cwnd could only grow to this value (of
128).  Now, records are allocated on demand as necessary---cwnd may
grow as it wishes.  The exceptional case of when memory is not
available is not handled gracefully.  Perhaps, cwnd should be capped
at that point.
Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dccp/ccids/ccid2.c

@@ -44,8 +44,6 @@ static int ccid2_debug;
 #define ccid2_pr_debug(format, a...)
 #endif
 
-static const int ccid2_seq_len = 128;
-
 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
 static void ccid2_hc_tx_check_sanity(const struct ccid2_hc_tx_sock *hctx)
 {
@@ -71,7 +69,6 @@ static void ccid2_hc_tx_check_sanity(const struct ccid2_hc_tx_sock *hctx)
 			BUG_ON(seqp->ccid2s_seq <= prev->ccid2s_seq);
 			BUG_ON(time_before(seqp->ccid2s_sent,
 					   prev->ccid2s_sent));
-			BUG_ON(len > ccid2_seq_len);
 
 			seqp = prev;
 		}
@@ -83,16 +80,57 @@ static void ccid2_hc_tx_check_sanity(const struct ccid2_hc_tx_sock *hctx)
 	do {
 		seqp = seqp->ccid2s_prev;
 		len++;
-		BUG_ON(len > ccid2_seq_len);
 	} while (seqp != hctx->ccid2hctx_seqh);
 
-	BUG_ON(len != ccid2_seq_len);
 	ccid2_pr_debug("total len=%d\n", len);
+	BUG_ON(len != hctx->ccid2hctx_seqbufc * CCID2_SEQBUF_LEN);
 }
 #else
 #define ccid2_hc_tx_check_sanity(hctx) do {} while (0)
 #endif
 
+static int ccid2_hc_tx_alloc_seq(struct ccid2_hc_tx_sock *hctx, int num,
+				 gfp_t gfp)
+{
+	struct ccid2_seq *seqp;
+	int i;
+
+	/* check if we have space to preserve the pointer to the buffer */
+	if (hctx->ccid2hctx_seqbufc >= (sizeof(hctx->ccid2hctx_seqbuf) /
+					sizeof(struct ccid2_seq*)))
+		return -ENOMEM;
+
+	/* allocate buffer and initialize linked list */
+	seqp = kmalloc(sizeof(*seqp) * num, gfp);
+	if (seqp == NULL)
+		return -ENOMEM;
+
+	for (i = 0; i < (num - 1); i++) {
+		seqp[i].ccid2s_next = &seqp[i + 1];
+		seqp[i + 1].ccid2s_prev = &seqp[i];
+	}
+	seqp[num - 1].ccid2s_next = seqp;
+	seqp->ccid2s_prev = &seqp[num - 1];
+
+	/* This is the first allocation.  Initiate the head and tail.  */
+	if (hctx->ccid2hctx_seqbufc == 0)
+		hctx->ccid2hctx_seqh = hctx->ccid2hctx_seqt = seqp;
+	else {
+		/* link the existing list with the one we just created */
+		hctx->ccid2hctx_seqh->ccid2s_next = seqp;
+		seqp->ccid2s_prev = hctx->ccid2hctx_seqh;
+
+		hctx->ccid2hctx_seqt->ccid2s_prev = &seqp[num - 1];
+		seqp[num - 1].ccid2s_next = hctx->ccid2hctx_seqt;
+	}
+
+	/* store the original pointer to the buffer so we can free it */
+	hctx->ccid2hctx_seqbuf[hctx->ccid2hctx_seqbufc] = seqp;
+	hctx->ccid2hctx_seqbufc++;
+
+	return 0;
+}
+
 static int ccid2_hc_tx_send_packet(struct sock *sk,
 				   struct sk_buff *skb, int len)
 {
@@ -231,6 +269,7 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, int len)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
+	struct ccid2_seq *next;
 	u64 seq;
 
 	ccid2_hc_tx_check_sanity(hctx);
@@ -250,15 +289,23 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, int len)
 	hctx->ccid2hctx_seqh->ccid2s_seq   = seq;
 	hctx->ccid2hctx_seqh->ccid2s_acked = 0;
 	hctx->ccid2hctx_seqh->ccid2s_sent  = jiffies;
-	hctx->ccid2hctx_seqh = hctx->ccid2hctx_seqh->ccid2s_next;
 
-	ccid2_pr_debug("cwnd=%d pipe=%d\n", hctx->ccid2hctx_cwnd,
-		       hctx->ccid2hctx_pipe);
+	next = hctx->ccid2hctx_seqh->ccid2s_next;
+	/* check if we need to alloc more space */
+	if (next == hctx->ccid2hctx_seqt) {
+		int rc;
 
-	if (hctx->ccid2hctx_seqh == hctx->ccid2hctx_seqt) {
-		/* XXX allocate more space */
-		WARN_ON(1);
+		ccid2_pr_debug("allocating more space in history\n");
+		rc = ccid2_hc_tx_alloc_seq(hctx, CCID2_SEQBUF_LEN, GFP_KERNEL);
+		BUG_ON(rc); /* XXX what do we do? */
+
+		next = hctx->ccid2hctx_seqh->ccid2s_next;
+		BUG_ON(next == hctx->ccid2hctx_seqt);
 	}
+	hctx->ccid2hctx_seqh = next;
+
+	ccid2_pr_debug("cwnd=%d pipe=%d\n", hctx->ccid2hctx_cwnd,
+		       hctx->ccid2hctx_pipe);
 
 	hctx->ccid2hctx_sent++;
 
@@ -674,8 +721,6 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
 {
         struct ccid2_hc_tx_sock *hctx = ccid_priv(ccid);
-	int seqcount = ccid2_seq_len;
-	int i;
 
 	hctx->ccid2hctx_cwnd	  = 1;
 	/* Initialize ssthresh to infinity.  This means that we will exit the
@@ -684,26 +729,12 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
 	 */
 	hctx->ccid2hctx_ssthresh  = ~0;
 	hctx->ccid2hctx_numdupack = 3;
+	hctx->ccid2hctx_seqbufc   = 0;
 
 	/* XXX init ~ to window size... */
-	hctx->ccid2hctx_seqbuf = kmalloc(sizeof(*hctx->ccid2hctx_seqbuf) *
-					 seqcount, gfp_any());
-	if (hctx->ccid2hctx_seqbuf == NULL)
+	if (ccid2_hc_tx_alloc_seq(hctx, CCID2_SEQBUF_LEN, GFP_ATOMIC) != 0)
 		return -ENOMEM;
 
-	for (i = 0; i < (seqcount - 1); i++) {
-		hctx->ccid2hctx_seqbuf[i].ccid2s_next =
-					&hctx->ccid2hctx_seqbuf[i + 1];
-		hctx->ccid2hctx_seqbuf[i + 1].ccid2s_prev =
-					&hctx->ccid2hctx_seqbuf[i];
-	}
-	hctx->ccid2hctx_seqbuf[seqcount - 1].ccid2s_next =
-					hctx->ccid2hctx_seqbuf;
-	hctx->ccid2hctx_seqbuf->ccid2s_prev =
-					&hctx->ccid2hctx_seqbuf[seqcount - 1];
-
-	hctx->ccid2hctx_seqh	 = hctx->ccid2hctx_seqbuf;
-	hctx->ccid2hctx_seqt	 = hctx->ccid2hctx_seqh;
 	hctx->ccid2hctx_sent	 = 0;
 	hctx->ccid2hctx_rto	 = 3 * HZ;
 	hctx->ccid2hctx_srtt	 = -1;
@@ -722,10 +753,13 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
 static void ccid2_hc_tx_exit(struct sock *sk)
 {
         struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
+	int i;
 
 	ccid2_hc_tx_kill_rto_timer(sk);
-	kfree(hctx->ccid2hctx_seqbuf);
-	hctx->ccid2hctx_seqbuf = NULL;
+
+	for (i = 0; i < hctx->ccid2hctx_seqbufc; i++)
+		kfree(hctx->ccid2hctx_seqbuf[i]);
+	hctx->ccid2hctx_seqbufc = 0;
 }
 
 static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)

net/dccp/ccids/ccid2.h

@@ -35,6 +35,9 @@ struct ccid2_seq {
 	struct ccid2_seq	*ccid2s_next;
 };
 
+#define CCID2_SEQBUF_LEN 256
+#define CCID2_SEQBUF_MAX 128
+
 /** struct ccid2_hc_tx_sock - CCID2 TX half connection
  *
  * @ccid2hctx_ssacks - ACKs recv in slow start
@@ -53,7 +56,8 @@ struct ccid2_hc_tx_sock {
 	unsigned int		ccid2hctx_ssthresh;
 	int			ccid2hctx_pipe;
 	int			ccid2hctx_numdupack;
-	struct ccid2_seq	*ccid2hctx_seqbuf;
+	struct ccid2_seq	*ccid2hctx_seqbuf[CCID2_SEQBUF_MAX];
+	int			ccid2hctx_seqbufc;
 	struct ccid2_seq	*ccid2hctx_seqh;
 	struct ccid2_seq	*ccid2hctx_seqt;
 	long			ccid2hctx_rto;