net/hsr: Better frame dispatch

This patch removes the separate paths for frames coming from the outside, and
frames sent from the HSR device, and instead makes all frames go through
hsr_forward_skb() in hsr_forward.c. This greatly improves code readability and
also opens up the possibility for future support of the HSR Interlink device
that is the basis for HSR RedBoxes and HSR QuadBoxes, as well as VLAN
compatibility.

Other improvements:
* A reduction in the number of times an skb is copied on machines without
  HAVE_EFFICIENT_UNALIGNED_ACCESS, which improves throughput somewhat.
* Headers are now created using the standard eth_header(), and using the
  standard hard_header_len.
* Each HSR slave now gets its own private skb, so slave-specific fields can be
  correctly set.

Signed-off-by: Arvid Brodin <arvid.brodin@alten.se>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 368 insertions, 0 deletions

diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
new file mode 100644
index 000000000000..7871ed6d3825
--- /dev/null
+++ b/net/hsr/hsr_forward.c
@@ -0,0 +1,368 @@
+/* Copyright 2011-2014 Autronica Fire and Security AS
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * Author(s):
+ *	2011-2014 Arvid Brodin, arvid.brodin@alten.se
+ */
+
+#include "hsr_forward.h"
+#include <linux/types.h>
+#include <linux/skbuff.h>
+#include <linux/etherdevice.h>
+#include <linux/if_vlan.h>
+#include "hsr_main.h"
+#include "hsr_framereg.h"
+
+
+struct hsr_node;
+
+struct hsr_frame_info {
+	struct sk_buff *skb_std;
+	struct sk_buff *skb_hsr;
+	struct hsr_port *port_rcv;
+	struct hsr_node *node_src;
+	u16 sequence_nr;
+	bool is_supervision;
+	bool is_vlan;
+	bool is_local_dest;
+	bool is_local_exclusive;
+};
+
+
+/* The uses I can see for these HSR supervision frames are:
+ * 1) Use the frames that are sent after node initialization ("HSR_TLV.Type =
+ *    22") to reset any sequence_nr counters belonging to that node. Useful if
+ *    the other node's counter has been reset for some reason.
+ *    --
+ *    Or not - resetting the counter and bridging the frame would create a
+ *    loop, unfortunately.
+ *
+ * 2) Use the LifeCheck frames to detect ring breaks. I.e. if no LifeCheck
+ *    frame is received from a particular node, we know something is wrong.
+ *    We just register these (as with normal frames) and throw them away.
+ *
+ * 3) Allow different MAC addresses for the two slave interfaces, using the
+ *    MacAddressA field.
+ */
+static bool is_supervision_frame(struct hsr_priv *hsr, struct sk_buff *skb)
+{
+	struct hsr_ethhdr_sp *hdr;
+
+	WARN_ON_ONCE(!skb_mac_header_was_set(skb));
+	hdr = (struct hsr_ethhdr_sp *) skb_mac_header(skb);
+
+	if (!ether_addr_equal(hdr->ethhdr.h_dest,
+			      hsr->sup_multicast_addr))
+		return false;
+
+	if (get_hsr_stag_path(&hdr->hsr_sup) != 0x0f)
+		return false;
+	if ((hdr->hsr_sup.HSR_TLV_Type != HSR_TLV_ANNOUNCE) &&
+	    (hdr->hsr_sup.HSR_TLV_Type != HSR_TLV_LIFE_CHECK))
+		return false;
+	if (hdr->hsr_sup.HSR_TLV_Length != 12)
+		return false;
+
+	return true;
+}
+
+
+static struct sk_buff *create_stripped_skb(struct sk_buff *skb_in,
+					   struct hsr_frame_info *frame)
+{
+	struct sk_buff *skb;
+	int copylen;
+	unsigned char *dst, *src;
+
+	skb_pull(skb_in, HSR_HLEN);
+	skb = __pskb_copy(skb_in, skb_headroom(skb_in) - HSR_HLEN, GFP_ATOMIC);
+	skb_push(skb_in, HSR_HLEN);
+	if (skb == NULL)
+		return NULL;
+
+	skb_reset_mac_header(skb);
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL)
+		skb->csum_start -= HSR_HLEN;
+
+	copylen = 2*ETH_ALEN;
+	if (frame->is_vlan)
+		copylen += VLAN_HLEN;
+	src = skb_mac_header(skb_in);
+	dst = skb_mac_header(skb);
+	memcpy(dst, src, copylen);
+
+	skb->protocol = eth_hdr(skb)->h_proto;
+	return skb;
+}
+
+static struct sk_buff *frame_get_stripped_skb(struct hsr_frame_info *frame,
+					      struct hsr_port *port)
+{
+	if (!frame->skb_std)
+		frame->skb_std = create_stripped_skb(frame->skb_hsr, frame);
+	return skb_clone(frame->skb_std, GFP_ATOMIC);
+}
+
+
+static void hsr_fill_tag(struct sk_buff *skb, struct hsr_frame_info *frame,
+			 struct hsr_port *port)
+{
+	struct hsr_ethhdr *hsr_ethhdr;
+	int lane_id;
+	int lsdu_size;
+
+	if (port->type == HSR_PT_SLAVE_A)
+		lane_id = 0;
+	else
+		lane_id = 1;
+
+	lsdu_size = skb->len - 14;
+	if (frame->is_vlan)
+		lsdu_size -= 4;
+
+	hsr_ethhdr = (struct hsr_ethhdr *) skb_mac_header(skb);
+
+	set_hsr_tag_path(&hsr_ethhdr->hsr_tag, lane_id);
+	set_hsr_tag_LSDU_size(&hsr_ethhdr->hsr_tag, lsdu_size);
+	hsr_ethhdr->hsr_tag.sequence_nr = htons(frame->sequence_nr);
+	hsr_ethhdr->hsr_tag.encap_proto = hsr_ethhdr->ethhdr.h_proto;
+	hsr_ethhdr->ethhdr.h_proto = htons(ETH_P_PRP);
+}
+
+static struct sk_buff *create_tagged_skb(struct sk_buff *skb_o,
+					 struct hsr_frame_info *frame,
+					 struct hsr_port *port)
+{
+	int movelen;
+	unsigned char *dst, *src;
+	struct sk_buff *skb;
+
+	/* Create the new skb with enough headroom to fit the HSR tag */
+	skb = __pskb_copy(skb_o, skb_headroom(skb_o) + HSR_HLEN, GFP_ATOMIC);
+	if (skb == NULL)
+		return NULL;
+	skb_reset_mac_header(skb);
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL)
+		skb->csum_start += HSR_HLEN;
+
+	movelen = ETH_HLEN;
+	if (frame->is_vlan)
+		movelen += VLAN_HLEN;
+
+	src = skb_mac_header(skb);
+	dst = skb_push(skb, HSR_HLEN);
+	memmove(dst, src, movelen);
+	skb_reset_mac_header(skb);
+
+	hsr_fill_tag(skb, frame, port);
+
+	return skb;
+}
+
+/* If the original frame was an HSR tagged frame, just clone it to be sent
+ * unchanged. Otherwise, create a private frame especially tagged for 'port'.
+ */
+static struct sk_buff *frame_get_tagged_skb(struct hsr_frame_info *frame,
+					    struct hsr_port *port)
+{
+	if (frame->skb_hsr)
+		return skb_clone(frame->skb_hsr, GFP_ATOMIC);
+
+	if ((port->type != HSR_PT_SLAVE_A) && (port->type != HSR_PT_SLAVE_B)) {
+		WARN_ONCE(1, "HSR: Bug: trying to create a tagged frame for a non-ring port");
+		return NULL;
+	}
+
+	return create_tagged_skb(frame->skb_std, frame, port);
+}
+
+
+static void hsr_deliver_master(struct sk_buff *skb, struct net_device *dev,
+			       struct hsr_node *node_src)
+{
+	bool was_multicast_frame;
+	int res;
+
+	was_multicast_frame = (skb->pkt_type == PACKET_MULTICAST);
+	hsr_addr_subst_source(node_src, skb);
+	skb_pull(skb, ETH_HLEN);
+	res = netif_rx(skb);
+	if (res == NET_RX_DROP) {
+		dev->stats.rx_dropped++;
+	} else {
+		dev->stats.rx_packets++;
+		dev->stats.rx_bytes += skb->len;
+		if (was_multicast_frame)
+			dev->stats.multicast++;
+	}
+}
+
+static int hsr_xmit(struct sk_buff *skb, struct hsr_port *port,
+		    struct hsr_frame_info *frame)
+{
+	if (frame->port_rcv->type == HSR_PT_MASTER) {
+		hsr_addr_subst_dest(frame->node_src, skb, port);
+
+		/* Address substitution (IEC62439-3 pp 26, 50): replace mac
+		 * address of outgoing frame with that of the outgoing slave's.
+		 */
+		ether_addr_copy(eth_hdr(skb)->h_source, port->dev->dev_addr);
+	}
+	return dev_queue_xmit(skb);
+}
+
+
+/* Forward the frame through all devices except:
+ * - Back through the receiving device
+ * - If it's a HSR frame: through a device where it has passed before
+ * - To the local HSR master only if the frame is directly addressed to it, or
+ *   a non-supervision multicast or broadcast frame.
+ *
+ * HSR slave devices should insert a HSR tag into the frame, or forward the
+ * frame unchanged if it's already tagged. Interlink devices should strip HSR
+ * tags if they're of the non-HSR type (but only after duplicate discard). The
+ * master device always strips HSR tags.
+ */
+static void hsr_forward_do(struct hsr_frame_info *frame)
+{
+	struct hsr_port *port;
+	struct sk_buff *skb;
+
+	hsr_for_each_port(frame->port_rcv->hsr, port) {
+		/* Don't send frame back the way it came */
+		if (port == frame->port_rcv)
+			continue;
+
+		/* Don't deliver locally unless we should */
+		if ((port->type == HSR_PT_MASTER) && !frame->is_local_dest)
+			continue;
+
+		/* Deliver frames directly addressed to us to master only */
+		if ((port->type != HSR_PT_MASTER) && frame->is_local_exclusive)
+			continue;
+
+		/* Don't send frame over port where it has been sent before */
+		if (hsr_register_frame_out(port, frame->node_src,
+					   frame->sequence_nr))
+			continue;
+
+		if (frame->is_supervision && (port->type == HSR_PT_MASTER)) {
+			hsr_handle_sup_frame(frame->skb_hsr,
+					     frame->node_src,
+					     frame->port_rcv);
+			continue;
+		}
+
+		if (port->type != HSR_PT_MASTER)
+			skb = frame_get_tagged_skb(frame, port);
+		else
+			skb = frame_get_stripped_skb(frame, port);
+		if (skb == NULL) {
+			/* FIXME: Record the dropped frame? */
+			continue;
+		}
+
+		skb->dev = port->dev;
+		if (port->type == HSR_PT_MASTER)
+			hsr_deliver_master(skb, port->dev, frame->node_src);
+		else
+			hsr_xmit(skb, port, frame);
+	}
+}
+
+
+static void check_local_dest(struct hsr_priv *hsr, struct sk_buff *skb,
+			     struct hsr_frame_info *frame)
+{
+	struct net_device *master_dev;
+
+	master_dev = hsr_port_get_hsr(hsr, HSR_PT_MASTER)->dev;
+
+	if (hsr_addr_is_self(hsr, eth_hdr(skb)->h_dest)) {
+		frame->is_local_exclusive = true;
+		skb->pkt_type = PACKET_HOST;
+	} else {
+		frame->is_local_exclusive = false;
+	}
+
+	if ((skb->pkt_type == PACKET_HOST) ||
+	    (skb->pkt_type == PACKET_MULTICAST) ||
+	    (skb->pkt_type == PACKET_BROADCAST)) {
+		frame->is_local_dest = true;
+	} else {
+		frame->is_local_dest = false;
+	}
+}
+
+
+static int hsr_fill_frame_info(struct hsr_frame_info *frame,
+			       struct sk_buff *skb, struct hsr_port *port)
+{
+	struct ethhdr *ethhdr;
+	unsigned long irqflags;
+
+	frame->is_supervision = is_supervision_frame(port->hsr, skb);
+	frame->node_src = hsr_get_node(&port->hsr->node_db, skb,
+				       frame->is_supervision);
+	if (frame->node_src == NULL)
+		return -1; /* Unknown node and !is_supervision, or no mem */
+
+	ethhdr = (struct ethhdr *) skb_mac_header(skb);
+	frame->is_vlan = false;
+	if (ethhdr->h_proto == htons(ETH_P_8021Q)) {
+		frame->is_vlan = true;
+		/* FIXME: */
+		WARN_ONCE(1, "HSR: VLAN not yet supported");
+	}
+	if (ethhdr->h_proto == htons(ETH_P_PRP)) {
+		frame->skb_std = NULL;
+		frame->skb_hsr = skb;
+		frame->sequence_nr = hsr_get_skb_sequence_nr(skb);
+	} else {
+		frame->skb_std = skb;
+		frame->skb_hsr = NULL;
+		/* Sequence nr for the master node */
+		spin_lock_irqsave(&port->hsr->seqnr_lock, irqflags);
+		frame->sequence_nr = port->hsr->sequence_nr;
+		port->hsr->sequence_nr++;
+		spin_unlock_irqrestore(&port->hsr->seqnr_lock, irqflags);
+	}
+
+	frame->port_rcv = port;
+	check_local_dest(port->hsr, skb, frame);
+
+	return 0;
+}
+
+/* Must be called holding rcu read lock (because of the port parameter) */
+void hsr_forward_skb(struct sk_buff *skb, struct hsr_port *port)
+{
+	struct hsr_frame_info frame;
+
+	if (skb_mac_header(skb) != skb->data) {
+		WARN_ONCE(1, "%s:%d: Malformed frame (port_src %s)\n",
+			  __FILE__, __LINE__, port->dev->name);
+		goto out_drop;
+	}
+
+	if (hsr_fill_frame_info(&frame, skb, port) < 0)
+		goto out_drop;
+	hsr_register_frame_in(frame.node_src, port, frame.sequence_nr);
+	hsr_forward_do(&frame);
+
+	if (frame.skb_hsr != NULL)
+		kfree_skb(frame.skb_hsr);
+	if (frame.skb_std != NULL)
+		kfree_skb(frame.skb_std);
+	return;
+
+out_drop:
+	port->dev->stats.tx_dropped++;
+	kfree_skb(skb);
+}