openflow/datapath/flow.c

/*
 * Distributed under the terms of the GNU GPL version 2.
 * Copyright (c) 2007, 2008 The Board of Trustees of The Leland 
 * Stanford Junior University
 */

#include "flow.h"
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/if_arp.h>
#include <net/llc_pdu.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/kernel.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/in.h>
#include <linux/rcupdate.h>

#include "openflow.h"
#include "compat.h"
#include "snap.h"

struct kmem_cache *flow_cache;

/* Internal function used to compare fields in flow. */
static inline
int flow_fields_match(const struct sw_flow_key *a, const struct sw_flow_key *b,
		uint16_t w)
{
	return ((w & OFPFW_IN_PORT || a->in_port == b->in_port)
		&& (w & OFPFW_DL_VLAN || a->dl_vlan == b->dl_vlan)
		&& (w & OFPFW_DL_SRC || !memcmp(a->dl_src, b->dl_src, ETH_ALEN))
		&& (w & OFPFW_DL_DST || !memcmp(a->dl_dst, b->dl_dst, ETH_ALEN))
		&& (w & OFPFW_DL_TYPE || a->dl_type == b->dl_type)
		&& (w & OFPFW_NW_SRC || a->nw_src == b->nw_src)
		&& (w & OFPFW_NW_DST || a->nw_dst == b->nw_dst)
		&& (w & OFPFW_NW_PROTO || a->nw_proto == b->nw_proto)
		&& (w & OFPFW_TP_SRC || a->tp_src == b->tp_src)
		&& (w & OFPFW_TP_DST || a->tp_dst == b->tp_dst));
}

/* Returns nonzero if 'a' and 'b' match, that is, if their fields are equal
 * modulo wildcards, zero otherwise. */
inline
int flow_matches(const struct sw_flow_key *a, const struct sw_flow_key *b)
{
	return flow_fields_match(a, b, (a->wildcards | b->wildcards));
}

/* Returns nonzero if 't' (the table entry's key) and 'd' (the key 
 * describing the deletion) match, that is, if their fields are 
 * equal modulo wildcards, zero otherwise.  If 'strict' is nonzero, the
 * wildcards must match in both 't_key' and 'd_key'.  Note that the
 * table's wildcards are ignored unless 'strict' is set. */
inline
int flow_del_matches(const struct sw_flow_key *t, const struct sw_flow_key *d, int strict)
{
	if (strict && (t->wildcards != d->wildcards))
		return 0;

	return flow_fields_match(t, d, d->wildcards);
}

void flow_extract_match(struct sw_flow_key* to, const struct ofp_match* from)
{
	to->wildcards = ntohs(from->wildcards) & OFPFW_ALL;
	to->in_port   = from->in_port;
	to->dl_vlan   = from->dl_vlan;
	memcpy(to->dl_src, from->dl_src, ETH_ALEN);
	memcpy(to->dl_dst, from->dl_dst, ETH_ALEN);
	to->dl_type   = from->dl_type;
	to->nw_src	  = from->nw_src;
	to->nw_dst	  = from->nw_dst;
	to->nw_proto  = from->nw_proto;
	to->tp_src	  = from->tp_src;
	to->tp_dst	  = from->tp_dst;
	memset(to->pad, '\0', sizeof(to->pad));
}

void flow_fill_match(struct ofp_match* to, const struct sw_flow_key* from)
{
	to->wildcards = htons(from->wildcards);
	to->in_port   = from->in_port;
	to->dl_vlan   = from->dl_vlan;
	memcpy(to->dl_src, from->dl_src, ETH_ALEN);
	memcpy(to->dl_dst, from->dl_dst, ETH_ALEN);
	to->dl_type   = from->dl_type;
	to->nw_src	  = from->nw_src;
	to->nw_dst	  = from->nw_dst;
	to->nw_proto  = from->nw_proto;
	to->tp_src	  = from->tp_src;
	to->tp_dst	  = from->tp_dst;
	memset(to->pad, '\0', sizeof(to->pad));
}

/* Returns true if 'flow' can be deleted and set up for a deferred free, false
 * if deletion has already been scheduled (by another thread).
 *
 * Caller must hold rcu_read_lock. */
int flow_del(struct sw_flow *flow)
{
	return !atomic_cmpxchg(&flow->deleted, 0, 1);
}

/* Allocates and returns a new flow with 'n_actions' action, using allocation
 * flags 'flags'.  Returns the new flow or a null pointer on failure. */
struct sw_flow *flow_alloc(int n_actions, gfp_t flags)
{
	struct sw_flow *flow = kmem_cache_alloc(flow_cache, flags);
	if (unlikely(!flow))
		return NULL;

	flow->n_actions = n_actions;
	flow->actions = kmalloc(n_actions * sizeof *flow->actions,
				flags);
	if (unlikely(!flow->actions) && n_actions > 0) {
		kmem_cache_free(flow_cache, flow);
		return NULL;
	}
	return flow;
}

/* Frees 'flow' immediately. */
void flow_free(struct sw_flow *flow)
{
	if (unlikely(!flow))
		return;
	kfree(flow->actions);
	kmem_cache_free(flow_cache, flow);
}

/* RCU callback used by flow_deferred_free. */
static void rcu_callback(struct rcu_head *rcu)
{
	struct sw_flow *flow = container_of(rcu, struct sw_flow, rcu);
	flow_free(flow);
}

/* Schedules 'flow' to be freed after the next RCU grace period.
 * The caller must hold rcu_read_lock for this to be sensible. */
void flow_deferred_free(struct sw_flow *flow)
{
	call_rcu(&flow->rcu, rcu_callback);
}

/* Prints a representation of 'key' to the kernel log. */
void print_flow(const struct sw_flow_key *key)
{
	printk("wild%04x port%04x:vlan%04x mac%02x:%02x:%02x:%02x:%02x:%02x"
			"->%02x:%02x:%02x:%02x:%02x:%02x "
			"proto%04x ip%u.%u.%u.%u->%u.%u.%u.%u port%d->%d\n",
			key->wildcards, ntohs(key->in_port), ntohs(key->dl_vlan),
			key->dl_src[0], key->dl_src[1], key->dl_src[2],
			key->dl_src[3], key->dl_src[4], key->dl_src[5],
			key->dl_dst[0], key->dl_dst[1], key->dl_dst[2],
			key->dl_dst[3], key->dl_dst[4], key->dl_dst[5],
			ntohs(key->dl_type),
			((unsigned char *)&key->nw_src)[0],
			((unsigned char *)&key->nw_src)[1],
			((unsigned char *)&key->nw_src)[2],
			((unsigned char *)&key->nw_src)[3],
			((unsigned char *)&key->nw_dst)[0],
			((unsigned char *)&key->nw_dst)[1],
			((unsigned char *)&key->nw_dst)[2],
			((unsigned char *)&key->nw_dst)[3],
			ntohs(key->tp_src), ntohs(key->tp_dst));
}

uint32_t hash_in6(const struct in6_addr *in)
{
	return (in->s6_addr32[0] ^ in->s6_addr32[1]
			^ in->s6_addr32[2] ^ in->s6_addr32[3]);
}

// with inspiration from linux/if_arp.h
struct arp_eth_hdr {
	uint16_t  ar_hrd;  /* format of hardware address    */
	uint16_t  ar_pro;  /* format of protocol address    */
	uint8_t   ar_hln;  /* length of hardware address    */
	uint8_t   ar_pln;  /* length of protocol address    */
	uint16_t  ar_op;   /* ARP opcode (command)          */

	uint8_t   ar_sha[ETH_ALEN]; /* source hardware addr */
	uint32_t  ar_sip;           /* source protocol addr */
	uint8_t   ar_tha[ETH_ALEN]; /* dest hardware addr   */
	uint32_t  ar_tip;           /* dest protocol addr   */
} __attribute__((packed));

/* Parses the Ethernet frame in 'skb', which was received on 'in_port',
 * and initializes 'key' to match. */
void flow_extract(struct sk_buff *skb, uint16_t in_port,
		  struct sw_flow_key *key)
{
	struct ethhdr *mac;
	struct udphdr *th;
	int nh_ofs, th_ofs;

	key->in_port = htons(in_port);
	key->wildcards = 0;
	memset(key->pad, '\0', sizeof(key->pad));

	/* This code doesn't check that skb->len is long enough to contain the
	 * MAC or network header.  With a 46-byte minimum length frame this
	 * assumption is always correct. */

	/* Doesn't verify checksums.  Should it? */

	/* Data link layer.  We only support Ethernet. */
	mac = eth_hdr(skb);
	nh_ofs = sizeof(struct ethhdr);
	if (likely(ntohs(mac->h_proto) >= OFP_DL_TYPE_ETH2_CUTOFF)) {
		/* This is an Ethernet II frame */
		key->dl_type = mac->h_proto;
	} else {
		/* This is an 802.2 frame */
		if (snap_get_ethertype(skb, &key->dl_type) != -EINVAL) {
			nh_ofs += sizeof(struct snap_hdr);
		} else {
			key->dl_type = OFP_DL_TYPE_NOT_ETH_TYPE;
			nh_ofs += sizeof(struct llc_pdu_un);
		}
	}

	/* Check for a VLAN tag */
	if (likely(key->dl_type != htons(ETH_P_8021Q))) {
		key->dl_vlan = htons(OFP_VLAN_NONE);
	} else {
		struct vlan_hdr *vh = (struct vlan_hdr *)(skb_mac_header(skb) + nh_ofs);
		key->dl_type = vh->h_vlan_encapsulated_proto;
		key->dl_vlan = vh->h_vlan_TCI & htons(VLAN_VID_MASK);
		nh_ofs += sizeof(*vh);
	}
	memcpy(key->dl_src, mac->h_source, ETH_ALEN);
	memcpy(key->dl_dst, mac->h_dest, ETH_ALEN);
	skb_set_network_header(skb, nh_ofs);

	/* Network layer. */
	if (likely(key->dl_type == htons(ETH_P_IP))) {
		struct iphdr *nh = ip_hdr(skb);
		key->nw_src = nh->saddr;
		key->nw_dst = nh->daddr;
		key->nw_proto = nh->protocol;
		th_ofs = nh_ofs + nh->ihl * 4;
		skb_set_transport_header(skb, th_ofs);

		/* Transport layer. */
		if ((key->nw_proto != IPPROTO_TCP && key->nw_proto != IPPROTO_UDP)
				|| skb->len < th_ofs + sizeof(struct udphdr)) {
			goto no_th;
		}
		th = udp_hdr(skb);
		key->tp_src = th->source;
		key->tp_dst = th->dest;

		return;
	} else if (key->dl_type == htons(ETH_P_IPV6)) {
		struct ipv6hdr *nh = ipv6_hdr(skb);
		key->nw_src = hash_in6(&nh->saddr);
		key->nw_dst = hash_in6(&nh->daddr);
		/* FIXME: Need to traverse next-headers until we find the
		 * upper-layer header. */
		key->nw_proto = 0;
		goto no_th;
	} else if (key->dl_type == htons(ETH_P_ARP)) {
		/* just barely within 46-byte minimum packet */
		struct arp_eth_hdr *ah = (struct arp_eth_hdr *)skb_network_header(skb);
		if (ah->ar_hrd == htons(ARPHRD_ETHER)
		    && ah->ar_pro == htons(ETH_P_IP)
		    && ah->ar_hln == ETH_ALEN
		    && ah->ar_pln == sizeof(key->nw_src))
		{
			/* check if sha/tha match dl_src/dl_dst? */
			key->nw_src = ah->ar_sip;
			key->nw_dst = ah->ar_tip;
			key->nw_proto = 0;
			goto no_th;
		}
	} else {
		/* Fall through. */
	}

	key->nw_src = 0;
	key->nw_dst = 0;
	key->nw_proto = 0;

no_th:
	key->tp_src = 0;
	key->tp_dst = 0;
}

/* Initializes the flow module.
 * Returns zero if successful or a negative error code. */
int flow_init(void)
{
	flow_cache = kmem_cache_create("sw_flow", sizeof(struct sw_flow), 0,
					0, NULL);
	if (flow_cache == NULL)
		return -ENOMEM;

	return 0;
}

/* Uninitializes the flow module. */
void flow_exit(void)
{
	kmem_cache_destroy(flow_cache);
}