MFC r266941, r266955

Needed for anticipated dummynet AQM MFC next week.

r266941 | hiren | 2014-06-01 00:28:24 -0700 (Sun, 01 Jun 2014) | 9 lines

ECN marking implenetation for dummynet.
Changes include both DCTCP and RFC 3168 ECN marking methodology.

DCTCP draft: http://tools.ietf.org/html/draft-bensley-tcpm-dctcp-00

Submitted by:	Midori Kato (aoimidori27@gmail.com)
Worked with:	Lars Eggert (lars@netapp.com)
Reviewed by:	luigi, hiren

r266955 | hiren | 2014-06-01 13:19:17 -0700 (Sun, 01 Jun 2014) | 5 lines

DNOLD_IS_ECN introduced by r266941 is not required.
DNOLD_* flags are for compat with old binaries.

Suggested by: luigi

Discussed with:	hiren
Relnotes:	yes

2 files changed, 78 insertions, 5 deletions

diff --git a/sys/netpfil/ipfw/ip_dn_io.c b/sys/netpfil/ipfw/ip_dn_io.c
index fb75198..1930733 100644
--- a/sys/netpfil/ipfw/ip_dn_io.c
+++ b/sys/netpfil/ipfw/ip_dn_io.c
@@ -337,6 +337,8 @@ red_drops (struct dn_queue *q, int len)
 		return (0);	/* accept packet */
 	}
 	if (q->avg >= fs->max_th) {	/* average queue >=  max threshold */
+		if (fs->fs.flags & DN_IS_ECN)
+			return (1);
 		if (fs->fs.flags & DN_IS_GENTLE_RED) {
 			/*
 			 * According to Gentle-RED, if avg is greater than
@@ -352,6 +354,8 @@ red_drops (struct dn_queue *q, int len)
 			return (1);
 		}
 	} else if (q->avg > fs->min_th) {
+		if (fs->fs.flags & DN_IS_ECN)
+			return (1);
 		/*
 		 * We compute p_b using the linear dropping function
 		 *	 p_b = c_1 * avg - c_2
@@ -384,6 +388,70 @@ red_drops (struct dn_queue *q, int len)
 }
 
 /*
+ * ECN/ECT Processing (partially adopted from altq)
+ */
+static int
+ecn_mark(struct mbuf* m)
+{
+	struct ip *ip;
+	ip = mtod(m, struct ip *);
+
+	switch (ip->ip_v) {
+	case IPVERSION:
+	{
+		u_int8_t otos;
+		int sum;
+
+		if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_NOTECT)
+			return (0);	/* not-ECT */
+		if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
+			return (1);	/* already marked */
+
+		/*
+		 * ecn-capable but not marked,
+		 * mark CE and update checksum
+		 */
+		otos = ip->ip_tos;
+		ip->ip_tos |= IPTOS_ECN_CE;
+		/*
+		 * update checksum (from RFC1624)
+		 *	   HC' = ~(~HC + ~m + m')
+		 */
+		sum = ~ntohs(ip->ip_sum) & 0xffff;
+		sum += (~otos & 0xffff) + ip->ip_tos;
+		sum = (sum >> 16) + (sum & 0xffff);
+		sum += (sum >> 16);  /* add carry */
+		ip->ip_sum = htons(~sum & 0xffff);
+		return (1);
+	}
+#ifdef INET6
+	case (IPV6_VERSION >> 4):
+	{
+		struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
+		u_int32_t flowlabel;
+
+		flowlabel = ntohl(ip6->ip6_flow);
+		if ((flowlabel >> 28) != 6)
+			return (0);	/* version mismatch! */
+		if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
+		    (IPTOS_ECN_NOTECT << 20))
+			return (0);	/* not-ECT */
+		if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
+		    (IPTOS_ECN_CE << 20))
+			return (1);	/* already marked */
+		/*
+		 * ecn-capable but not marked, mark CE
+		 */
+		flowlabel |= (IPTOS_ECN_CE << 20);
+		ip6->ip6_flow = htonl(flowlabel);
+		return (1);
+	}
+#endif
+	}
+	return (0);
+}
+
+/*
  * Enqueue a packet in q, subject to space and queue management policy
  * (whose parameters are in q->fs).
  * Update stats for the queue and the scheduler.
@@ -414,8 +482,10 @@ dn_enqueue(struct dn_queue *q, struct mbuf* m, int drop)
 		goto drop;
 	if (f->plr && random() < f->plr)
 		goto drop;
-	if (f->flags & DN_IS_RED && red_drops(q, m->m_pkthdr.len))
-		goto drop;
+	if (f->flags & DN_IS_RED && red_drops(q, m->m_pkthdr.len)) {
+		if (!(f->flags & DN_IS_ECN) || !ecn_mark(m))
+			goto drop;
+	}
 	if (f->flags & DN_QSIZE_BYTES) {
 		if (q->ni.len_bytes > f->qsize)
 			goto drop;
@@ -427,14 +497,14 @@ dn_enqueue(struct dn_queue *q, struct mbuf* m, int drop)
 	q->ni.len_bytes += len;
 	ni->length++;
 	ni->len_bytes += len;
-	return 0;
+	return (0);
 
 drop:
 	io_pkt_drop++;
 	q->ni.drops++;
 	ni->drops++;
 	FREE_PKT(m);
-	return 1;
+	return (1);
 }
 
 /*
diff --git a/sys/netpfil/ipfw/ip_dummynet.c b/sys/netpfil/ipfw/ip_dummynet.c
index 3a12120..58b4e61 100644
--- a/sys/netpfil/ipfw/ip_dummynet.c
+++ b/sys/netpfil/ipfw/ip_dummynet.c
@@ -1073,7 +1073,10 @@ config_red(struct dn_fsk *fs)
 	fs->min_th = SCALE(fs->fs.min_th);
 	fs->max_th = SCALE(fs->fs.max_th);
 
-	fs->c_1 = fs->max_p / (fs->fs.max_th - fs->fs.min_th);
+	if (fs->fs.max_th == fs->fs.min_th)
+		fs->c_1 = fs->max_p;
+	else
+		fs->c_1 = SCALE((int64_t)(fs->max_p)) / (fs->fs.max_th - fs->fs.min_th);
 	fs->c_2 = SCALE_MUL(fs->c_1, SCALE(fs->fs.min_th));
 
 	if (fs->fs.flags & DN_IS_GENTLE_RED) {