C++ skb_share_check函数代码示例

static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
           struct packet_type *pt, struct net_device *orig_dev)
{
    struct arphdr *arp;

    /* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
    if (!pskb_may_pull(skb, arp_hdr_len(dev)))
        goto freeskb;

    arp = arp_hdr(skb);
    if (arp->ar_hln != dev->addr_len ||
        dev->flags & IFF_NOARP ||
        skb->pkt_type == PACKET_OTHERHOST ||
        skb->pkt_type == PACKET_LOOPBACK ||
        arp->ar_pln != 4)
        goto freeskb;

    if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
        goto out_of_mem;

    memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));

    return NF_HOOK(NF_ARP, NF_ARP_IN, skb, dev, NULL, arp_process);

freeskb:
    kfree_skb(skb);
out_of_mem:
    return 0;
}

int arp_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
{
	struct arphdr *arp;

	/* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
	if (!pskb_may_pull(skb, (sizeof(struct arphdr) +
				 (2 * dev->addr_len) +
				 (2 * sizeof(u32)))))
		goto freeskb;

	arp = skb->nh.arph;
	if (arp->ar_hln != dev->addr_len ||
	    dev->flags & IFF_NOARP ||
	    skb->pkt_type == PACKET_OTHERHOST ||
	    skb->pkt_type == PACKET_LOOPBACK ||
	    arp->ar_pln != 4)
		goto freeskb;

	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
		goto out_of_mem;

	return NF_HOOK(NF_ARP, NF_ARP_IN, skb, dev, NULL, arp_process);

freeskb:
	kfree_skb(skb);
out_of_mem:
	return 0;
}

/* Must be called with rcu_read_lock. */
static void netdev_port_receive(struct sk_buff *skb)
{
	struct vport *vport;

	vport = ovs_netdev_get_vport(skb->dev);
	if (unlikely(!vport))
		goto error;

	if (unlikely(skb_warn_if_lro(skb)))
		goto error;

	/* Make our own copy of the packet.  Otherwise we will mangle the
	 * packet for anyone who came before us (e.g. tcpdump via AF_PACKET).
	 */
	skb = skb_share_check(skb, GFP_ATOMIC);
	if (unlikely(!skb))
		return;

	skb_push(skb, ETH_HLEN);
	skb_postpush_rcsum(skb, skb->data, ETH_HLEN);
	ovs_vport_receive(vport, skb, skb_tunnel_info(skb));
	return;
error:
	kfree_skb(skb);
}

/* Must be called with rcu_read_lock. */
static void netdev_port_receive(struct vport *vport, struct sk_buff *skb)
{
	if (unlikely(!vport)) {
		kfree_skb(skb);
		return;
	}

	/* Make our own copy of the packet.  Otherwise we will mangle the
	 * packet for anyone who came before us (e.g. tcpdump via AF_PACKET).
	 * (No one comes after us, since we tell handle_bridge() that we took
	 * the packet.) */
	skb = skb_share_check(skb, GFP_ATOMIC);
	if (unlikely(!skb))
		return;

	skb_push(skb, ETH_HLEN);

	if (unlikely(compute_ip_summed(skb, false))) {
		kfree_skb(skb);
		return;
	}
	vlan_copy_skb_tci(skb);

	ovs_vport_receive(vport, skb);
}

struct sk_buff *vlan_untag(struct sk_buff *skb)
{
	struct vlan_hdr *vhdr;
	u16 vlan_tci;

	if (unlikely(vlan_tx_tag_present(skb))) {
		/* vlan_tci is already set-up so leave this for another time */
		return skb;
	}

	skb = skb_share_check(skb, GFP_ATOMIC);
	if (unlikely(!skb))
		goto err_free;

	if (unlikely(!pskb_may_pull(skb, VLAN_HLEN)))
		goto err_free;

	vhdr = (struct vlan_hdr *) skb->data;
	vlan_tci = ntohs(vhdr->h_vlan_TCI);
	__vlan_hwaccel_put_tag(skb, vlan_tci);

	skb_pull_rcsum(skb, VLAN_HLEN);
	vlan_set_encap_proto(skb, vhdr);

	skb = vlan_reorder_header(skb);
	if (unlikely(!skb))
		goto err_free;

	return skb;

err_free:
	kfree_skb(skb);
	return NULL;
}

bool vlan_do_receive(struct sk_buff **skbp, bool last_handler)
{
	struct sk_buff *skb = *skbp;
	u16 vlan_id = skb->vlan_tci & VLAN_VID_MASK;
	struct net_device *vlan_dev;
	struct vlan_pcpu_stats *rx_stats;

	vlan_dev = vlan_find_dev(skb->dev, vlan_id);
	if (!vlan_dev) {
		/* Only the last call to vlan_do_receive() should change
		 * pkt_type to PACKET_OTHERHOST
		 */
		if (vlan_id && last_handler)
			skb->pkt_type = PACKET_OTHERHOST;
		return false;
	}

	skb = *skbp = skb_share_check(skb, GFP_ATOMIC);
	if (unlikely(!skb))
		return false;

	skb->dev = vlan_dev;
	if (skb->pkt_type == PACKET_OTHERHOST) {
		/* Our lower layer thinks this is not local, let's make sure.
		 * This allows the VLAN to have a different MAC than the
		 * underlying device, and still route correctly. */
		if (ether_addr_equal(eth_hdr(skb)->h_dest, vlan_dev->dev_addr))
			skb->pkt_type = PACKET_HOST;
	}

	if (!(vlan_dev_priv(vlan_dev)->flags & VLAN_FLAG_REORDER_HDR)) {
		unsigned int offset = skb->data - skb_mac_header(skb);

		/*
		 * vlan_insert_tag expect skb->data pointing to mac header.
		 * So change skb->data before calling it and change back to
		 * original position later
		 */
		skb_push(skb, offset);
		skb = *skbp = vlan_insert_tag(skb, skb->vlan_tci);
		if (!skb)
			return false;
		skb_pull(skb, offset + VLAN_HLEN);
		skb_reset_mac_len(skb);
	}

	skb->priority = vlan_get_ingress_priority(vlan_dev, skb->vlan_tci);
	skb->vlan_tci = 0;

	rx_stats = this_cpu_ptr(vlan_dev_priv(vlan_dev)->vlan_pcpu_stats);

	u64_stats_update_begin(&rx_stats->syncp);
	rx_stats->rx_packets++;
	rx_stats->rx_bytes += skb->len;
	if (skb->pkt_type == PACKET_MULTICAST)
		rx_stats->rx_multicast++;
	u64_stats_update_end(&rx_stats->syncp);

	return true;
}

/* Must be called with rcu_read_lock. */
static void netdev_port_receive(struct vport *vport, struct sk_buff *skb)
{
	if (unlikely(!vport))
		goto error;

	if (unlikely(skb_warn_if_lro(skb)))
		goto error;

	/* Make our own copy of the packet.  Otherwise we will mangle the
	 * packet for anyone who came before us (e.g. tcpdump via AF_PACKET).
	 * (No one comes after us, since we tell handle_bridge() that we took
	 * the packet.)
	 */
	skb = skb_share_check(skb, GFP_ATOMIC);
	if (unlikely(!skb))
		return;

	skb_push(skb, ETH_HLEN);
	ovs_skb_postpush_rcsum(skb, skb->data, ETH_HLEN);

	ovs_vport_receive(vport, skb, NULL);
	return;

error:
	kfree_skb(skb);
}

int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
{
	struct ipv6hdr *hdr;
	u32 		pkt_len;

	if (skb->pkt_type == PACKET_OTHERHOST)
		goto drop;

	IP6_INC_STATS_BH(InReceives);

	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
		IP6_INC_STATS_BH(InDiscards);
		goto out;
	}

	/* Store incoming device index. When the packet will
	   be queued, we cannot refer to skb->dev anymore.
	 */
	IP6CB(skb)->iif = dev->ifindex;

	if (skb->len < sizeof(struct ipv6hdr))
		goto err;

	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr))) {
		IP6_INC_STATS_BH(InHdrErrors);
		goto drop;
	}

	hdr = skb->nh.ipv6h;

	if (hdr->version != 6)
		goto err;

	pkt_len = ntohs(hdr->payload_len);

	/* pkt_len may be zero if Jumbo payload option is present */
	if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
		if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
			goto truncated;
		if (pkt_len + sizeof(struct ipv6hdr) < skb->len) {
			if (__pskb_trim(skb, pkt_len + sizeof(struct ipv6hdr))){
				IP6_INC_STATS_BH(InHdrErrors);
				goto drop;
			}
			hdr = skb->nh.ipv6h;
			if (skb->ip_summed == CHECKSUM_HW)
				skb->ip_summed = CHECKSUM_NONE;
		}
	}

	if (hdr->nexthdr == NEXTHDR_HOP) {
		skb->h.raw = (u8*)(hdr+1);
		if (ipv6_parse_hopopts(skb, offsetof(struct ipv6hdr, nexthdr)) < 0) {
			IP6_INC_STATS_BH(InHdrErrors);
			return 0;
		}
		hdr = skb->nh.ipv6h;
	}

/*
 * Return NULL if skb is handled
 * note: already called with rcu_read_lock
 */
struct sk_buff *br_handle_frame(struct sk_buff *skb)
{
	struct net_bridge_port *p;
	const unsigned char *dest = eth_hdr(skb)->h_dest;
	int (*rhook)(struct sk_buff *skb);

	if (skb->pkt_type == PACKET_LOOPBACK)
		return skb;

	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
		goto drop;

	skb = skb_share_check(skb, GFP_ATOMIC);
	if (!skb)
		return NULL;

	p = br_port_get_rcu(skb->dev);

	if (unlikely(is_link_local(dest))) {
		/* Pause frames shouldn't be passed up by driver anyway */
		if (skb->protocol == htons(ETH_P_PAUSE))
			goto drop;

		/* If STP is turned off, then forward */
		if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
			goto forward;

		if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
			    NULL, br_handle_local_finish))
			return NULL;	/* frame consumed by filter */
		else
			return skb;	/* continue processing */
	}

forward:
	switch (p->state) {
	case BR_STATE_FORWARDING:
		rhook = rcu_dereference(br_should_route_hook);
		if (rhook != NULL) {
			if (rhook(skb))
				return skb;
			dest = eth_hdr(skb)->h_dest;
		}
		/* fall through */
	case BR_STATE_LEARNING:
		if (!compare_ether_addr(p->br->dev->dev_addr, dest))
			skb->pkt_type = PACKET_HOST;

		NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
			br_handle_frame_finish);
		break;
	default:
drop:
		kfree_skb(skb);
	}
	return NULL;
}

struct sk_buff *xip_trim_packet_if_needed(struct sk_buff *skb, u32 mtu)
{
	if (likely(skb->len <= mtu))
		return skb;

	BUG_ON(mtu < XIP_MIN_MTU);
	skb = skb_share_check(skb, GFP_ATOMIC);
	if (likely(skb))
		__skb_trim(skb, mtu);
	return skb;
}

static int vcan_tx(struct sk_buff *skb, struct net_device *dev)
{
	struct can_frame *cf = (struct can_frame *)skb->data;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,23)
	struct net_device_stats *stats = &dev->stats;
#else
	struct net_device_stats *stats = netdev_priv(dev);
#endif
	int loop;

	if (can_dropped_invalid_skb(dev, skb))
		return NETDEV_TX_OK;

	stats->tx_packets++;
	stats->tx_bytes += cf->can_dlc;

	/* set flag whether this packet has to be looped back */
	loop = skb->pkt_type == PACKET_LOOPBACK;

	if (!echo) {
		/* no echo handling available inside this driver */

		if (loop) {
			/*
			 * only count the packets here, because the
			 * CAN core already did the echo for us
			 */
			stats->rx_packets++;
			stats->rx_bytes += cf->can_dlc;
		}
		kfree_skb(skb);
		return NETDEV_TX_OK;
	}

	/* perform standard echo handling for CAN network interfaces */

	if (loop) {
		struct sock *srcsk = skb->sk;

		skb = skb_share_check(skb, GFP_ATOMIC);
		if (!skb)
			return NETDEV_TX_OK;

		/* receive with packet counting */
		skb->sk = srcsk;
		vcan_rx(skb, dev);
	} else {
		/* no looped packets => no counting */
		kfree_skb(skb);
	}
	return NETDEV_TX_OK;
}

/**
 *	llc_rcv - 802.2 entry point from net lower layers
 *	@skb: received pdu
 *	@dev: device that receive pdu
 *	@pt: packet type
 *
 *	When the system receives a 802.2 frame this function is called. It
 *	checks SAP and connection of received pdu and passes frame to
 *	llc_{station,sap,conn}_rcv for sending to proper state machine. If
 *	the frame is related to a busy connection (a connection is sending
 *	data now), it queues this frame in the connection's backlog.
 */
int llc_rcv(struct sk_buff *skb, struct net_device *dev,
	    struct packet_type *pt)
{
	struct llc_sap *sap;
	struct llc_pdu_sn *pdu;
	int dest;

	/*
	 * When the interface is in promisc. mode, drop all the crap that it
	 * receives, do not try to analyse it.
	 */
	if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
		dprintk("%s: PACKET_OTHERHOST\n", __FUNCTION__);
		goto drop;
	}
	skb = skb_share_check(skb, GFP_ATOMIC);
	if (unlikely(!skb))
		goto out;
	if (unlikely(!llc_fixup_skb(skb)))
		goto drop;
	pdu = llc_pdu_sn_hdr(skb);
	if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
	       goto handle_station;
	sap = llc_sap_find(pdu->dsap);
	if (unlikely(!sap)) {/* unknown SAP */
		dprintk("%s: llc_sap_find(%02X) failed!\n", __FUNCTION__,
		        pdu->dsap);
		goto drop;
	}
	/*
	 * First the upper layer protocols that don't need the full
	 * LLC functionality
	 */
	if (sap->rcv_func) {
		sap->rcv_func(skb, dev, pt);
		goto out;
	}
	dest = llc_pdu_type(skb);
	if (unlikely(!dest || !llc_type_handlers[dest - 1]))
		goto drop;
	llc_type_handlers[dest - 1](sap, skb);
out:
	return 0;
drop:
	kfree_skb(skb);
	goto out;
handle_station:
	if (!llc_station_handler)
		goto drop;
	llc_station_handler(skb);
	goto out;
}

/*
 * Called via br_handle_frame_hook.
 * Return NULL if skb is handled
 * note: already called with rcu_read_lock (preempt_disabled)
 */
struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
{
	const unsigned char *dest = eth_hdr(skb)->h_dest;
	int (*rhook)(struct sk_buff *skb);

	//源MAC地址为非法，返回错误，丢弃数据包
	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
		goto drop;

	skb = skb_share_check(skb, GFP_ATOMIC);
	if (!skb)
		return NULL;

	if (unlikely(is_link_local(dest))) 
	{
		/* Pause frames shouldn't be passed up by driver anyway */
		if (skb->protocol == htons(ETH_P_PAUSE))
			goto drop;

		/* Process STP BPDU's through normal netif_receive_skb() path */
		if (p->br->stp_enabled != BR_NO_STP)
		{
			if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev, NULL, br_handle_local_finish))
				return NULL;
			else
				return skb;
		}
	}

	switch (p->state) 
	{
	case BR_STATE_FORWARDING:
		rhook = rcu_dereference(br_should_route_hook);
		if (rhook != NULL) 
		{
			if (rhook(skb))
				return skb;
			dest = eth_hdr(skb)->h_dest;
		}
		/* fall through */
	case BR_STATE_LEARNING: //如果网桥状态处于学习状态，则更新数据库
		if (!compare_ether_addr(p->br->dev->dev_addr, dest))
			skb->pkt_type = PACKET_HOST;

		NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL, br_handle_frame_finish);
		break;
	default:
drop:
		kfree_skb(skb);
	}
	return NULL;
}

/* 
 * (1) len doesn't include the header by default.  I want this. 
 */
static int
aoenet_rcv(struct sk_buff *skb, struct net_device *ifp, struct packet_type *pt, struct net_device *orig_dev)
{
	struct aoe_hdr *h;
	u32 n;

	if (dev_net(ifp) != &init_net)
		goto exit;

	skb = skb_share_check(skb, GFP_ATOMIC);
	if (skb == NULL)
		return 0;
	if (skb_linearize(skb))
		goto exit;
	if (!is_aoe_netif(ifp))
		goto exit;
	skb_push(skb, ETH_HLEN);	/* (1) */

	h = (struct aoe_hdr *) skb_mac_header(skb);
	n = get_unaligned_be32(&h->tag);
	if ((h->verfl & AOEFL_RSP) == 0 || (n & 1<<31))
		goto exit;

	if (h->verfl & AOEFL_ERR) {
		n = h->err;
		if (n > NECODES)
			n = 0;
		if (net_ratelimit())
			printk(KERN_ERR
				"%s%d.%[email protected]%s; ecode=%d '%s'\n",
				"aoe: error packet from ",
				get_unaligned_be16(&h->major),
				h->minor, skb->dev->name,
				h->err, aoe_errlist[n]);
		goto exit;
	}

	switch (h->cmd) {
	case AOECMD_ATA:
		aoecmd_ata_rsp(skb);
		break;
	case AOECMD_CFG:
		aoecmd_cfg_rsp(skb);
		break;
	default:
		printk(KERN_INFO "aoe: unknown cmd %d\n", h->cmd);
	}
exit:
	dev_kfree_skb(skb);
	return 0;
}

static inline struct sk_buff *vlan_check_reorder_header(struct sk_buff *skb)
{
	if (VLAN_DEV_INFO(skb->dev)->flags & 1) {
		skb = skb_share_check(skb, GFP_ATOMIC);
		if (skb) {
			/* Lifted from Gleb's VLAN code... */
			memmove(skb->data - ETH_HLEN,
				skb->data - VLAN_ETH_HLEN, 12);
			skb->mac.raw += VLAN_HLEN;
		}
	}

	return skb;
}