C++ dev_hold函数代码示例

static
struct net_device *ipmr_new_tunnel(struct vifctl *v)
{
	struct net_device  *dev;

	dev = __dev_get_by_name(&init_net, "tunl0");

	if (dev) {
		const struct net_device_ops *ops = dev->netdev_ops;
		int err;
		struct ifreq ifr;
		struct ip_tunnel_parm p;
		struct in_device  *in_dev;

		memset(&p, 0, sizeof(p));
		p.iph.daddr = v->vifc_rmt_addr.s_addr;
		p.iph.saddr = v->vifc_lcl_addr.s_addr;
		p.iph.version = 4;
		p.iph.ihl = 5;
		p.iph.protocol = IPPROTO_IPIP;
		sprintf(p.name, "dvmrp%d", v->vifc_vifi);
		ifr.ifr_ifru.ifru_data = (__force void __user *)&p;

		if (ops->ndo_do_ioctl) {
			mm_segment_t oldfs = get_fs();

			set_fs(KERNEL_DS);
			err = ops->ndo_do_ioctl(dev, &ifr, SIOCADDTUNNEL);
			set_fs(oldfs);
		} else
			err = -EOPNOTSUPP;

		dev = NULL;

		if (err == 0 && (dev = __dev_get_by_name(&init_net, p.name)) != NULL) {
			dev->flags |= IFF_MULTICAST;

			in_dev = __in_dev_get_rtnl(dev);
			if (in_dev == NULL)
				goto failure;

			ipv4_devconf_setall(in_dev);
			IPV4_DEVCONF(in_dev->cnf, RP_FILTER) = 0;

			if (dev_open(dev))
				goto failure;
			dev_hold(dev);
		}
	}
	return dev;

failure:
	/* allow the register to be completed before unregistering. */
	rtnl_unlock();
	rtnl_lock();

	unregister_netdevice(dev);
	return NULL;
}

static struct ip_tunnel * ipip_tunnel_locate(struct ip_tunnel_parm *parms, int create)
{
    u32 remote = parms->iph.daddr;
    u32 local = parms->iph.saddr;
    struct ip_tunnel *t, **tp, *nt;
    struct net_device *dev;
    unsigned h = 0;
    int prio = 0;
    char name[IFNAMSIZ];

    if (remote) {
        prio |= 2;
        h ^= HASH(remote);
    }
    if (local) {
        prio |= 1;
        h ^= HASH(local);
    }
    for (tp = &tunnels[prio][h]; (t = *tp) != NULL; tp = &t->next) {
        if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr)
            return t;
    }
    if (!create)
        return NULL;

    if (parms->name[0])
        strlcpy(name, parms->name, IFNAMSIZ);
    else {
        int i;
        for (i=1; i<100; i++) {
            sprintf(name, "tunl%d", i);
            if (__dev_get_by_name(name) == NULL)
                break;
        }
        if (i==100)
            goto failed;
    }

    dev = alloc_netdev(sizeof(*t), name, ipip_tunnel_setup);
    if (dev == NULL)
        return NULL;

    nt = dev->priv;
    SET_MODULE_OWNER(dev);
    dev->init = ipip_tunnel_init;
    nt->parms = *parms;

    if (register_netdevice(dev) < 0) {
        free_netdev(dev);
        goto failed;
    }

    dev_hold(dev);
    ipip_tunnel_link(nt);
    return nt;

failed:
    return NULL;
}

int register_vlan_dev(struct net_device *dev)
{
	struct vlan_dev_info *vlan = vlan_dev_info(dev);
	struct net_device *real_dev = vlan->real_dev;
	const struct net_device_ops *ops = real_dev->netdev_ops;
	u16 vlan_id = vlan->vlan_id;
	struct vlan_group *grp, *ngrp = NULL;
	int err;

	grp = rtnl_dereference(real_dev->vlgrp);
	if (!grp) {
		ngrp = grp = vlan_group_alloc(real_dev);
		if (!grp)
			return -ENOBUFS;
		err = vlan_gvrp_init_applicant(real_dev);
		if (err < 0)
			goto out_free_group;
	}

	err = vlan_group_prealloc_vid(grp, vlan_id);
	if (err < 0)
		goto out_uninit_applicant;

	err = register_netdevice(dev);
	if (err < 0)
		goto out_uninit_applicant;

	/* Account for reference in struct vlan_dev_info */
	dev_hold(real_dev);

	netif_stacked_transfer_operstate(real_dev, dev);
	linkwatch_fire_event(dev); /* _MUST_ call rfc2863_policy() */

	/* So, got the sucker initialized, now lets place
	 * it into our local structure.
	 */
	vlan_group_set_device(grp, vlan_id, dev);
	grp->nr_vlans++;

	if (ngrp) {
		if (ops->ndo_vlan_rx_register)
			ops->ndo_vlan_rx_register(real_dev, ngrp);
		rcu_assign_pointer(real_dev->vlgrp, ngrp);
	}
	if (real_dev->features & NETIF_F_HW_VLAN_FILTER)
		ops->ndo_vlan_rx_add_vid(real_dev, vlan_id);

	return 0;

out_uninit_applicant:
	if (ngrp)
		vlan_gvrp_uninit_applicant(real_dev);
out_free_group:
	if (ngrp) {
		/* Free the group, after all cpu's are done. */
		call_rcu(&ngrp->rcu, vlan_rcu_free);
	}
	return err;
}

static int pim6_rcv(struct sk_buff *skb)
{
	struct pimreghdr *pim;
	struct ipv6hdr   *encap;
	struct net_device  *reg_dev = NULL;
	struct net *net = dev_net(skb->dev);
	int reg_vif_num = net->ipv6.mroute_reg_vif_num;

	if (!pskb_may_pull(skb, sizeof(*pim) + sizeof(*encap)))
		goto drop;

	pim = (struct pimreghdr *)skb_transport_header(skb);
	if (pim->type != ((PIM_VERSION << 4) | PIM_REGISTER) ||
	    (pim->flags & PIM_NULL_REGISTER) ||
	    (csum_ipv6_magic(&ipv6_hdr(skb)->saddr, &ipv6_hdr(skb)->daddr,
			     sizeof(*pim), IPPROTO_PIM,
			     csum_partial((void *)pim, sizeof(*pim), 0)) &&
	     csum_fold(skb_checksum(skb, 0, skb->len, 0))))
		goto drop;

	/* check if the inner packet is destined to mcast group */
	encap = (struct ipv6hdr *)(skb_transport_header(skb) +
				   sizeof(*pim));

	if (!ipv6_addr_is_multicast(&encap->daddr) ||
	    encap->payload_len == 0 ||
	    ntohs(encap->payload_len) + sizeof(*pim) > skb->len)
		goto drop;

	read_lock(&mrt_lock);
	if (reg_vif_num >= 0)
		reg_dev = net->ipv6.vif6_table[reg_vif_num].dev;
	if (reg_dev)
		dev_hold(reg_dev);
	read_unlock(&mrt_lock);

	if (reg_dev == NULL)
		goto drop;

	skb->mac_header = skb->network_header;
	skb_pull(skb, (u8 *)encap - skb->data);
	skb_reset_network_header(skb);
	skb->dev = reg_dev;
	skb->protocol = htons(ETH_P_IPV6);
	skb->ip_summed = 0;
	skb->pkt_type = PACKET_HOST;
	skb_dst_drop(skb);
	reg_dev->stats.rx_bytes += skb->len;
	reg_dev->stats.rx_packets++;
	nf_reset(skb);
	netif_rx(skb);
	dev_put(reg_dev);
	return 0;
 drop:
	kfree_skb(skb);
	return 0;
}

static int
ip6ip6_fb_tnl_dev_init(struct net_device *dev)
{
	struct ip6_tnl *t = netdev_priv(dev);
	ip6ip6_tnl_dev_init_gen(dev);
	dev_hold(dev);
	tnls_wc[0] = t;
	return 0;
}

void __netdev_watchdog_up(struct net_device *dev)
{
	if (dev->tx_timeout) {
		if (dev->watchdog_timeo <= 0)
			dev->watchdog_timeo = 5*HZ;
		if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
			dev_hold(dev);
	}
}

int ipv6_sock_mc_join(struct sock *sk, int ifindex, struct in6_addr *addr)
{
	struct net_device *dev = NULL;
	struct ipv6_mc_socklist *mc_lst;
	struct ipv6_pinfo *np = &sk->net_pinfo.af_inet6;
	int err;

	if (!(ipv6_addr_type(addr) & IPV6_ADDR_MULTICAST))
		return -EINVAL;

	mc_lst = sock_kmalloc(sk, sizeof(struct ipv6_mc_socklist), GFP_KERNEL);

	if (mc_lst == NULL)
		return -ENOMEM;

	mc_lst->next = NULL;
	memcpy(&mc_lst->addr, addr, sizeof(struct in6_addr));
	mc_lst->ifindex = ifindex;

	if (ifindex == 0) {
		struct rt6_info *rt;
		rt = rt6_lookup(addr, NULL, 0, 0);
		if (rt) {
			dev = rt->rt6i_dev;
			dev_hold(dev);
			dst_release(&rt->u.dst);
		}
	} else
		dev = dev_get_by_index(ifindex);

	if (dev == NULL) {
		sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
		return -ENODEV;
	}

	/*
	 *	now add/increase the group membership on the device
	 */

	err = ipv6_dev_mc_inc(dev, addr);

	if (err) {
		sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
		dev_put(dev);
		return err;
	}

	write_lock_bh(&ipv6_sk_mc_lock);
	mc_lst->next = np->ipv6_mc_list;
	np->ipv6_mc_list = mc_lst;
	write_unlock_bh(&ipv6_sk_mc_lock);

	dev_put(dev);

	return 0;
}

void __netdev_watchdog_up(struct net_device *dev)
{
	if (dev->netdev_ops->ndo_tx_timeout) {
		if (dev->watchdog_timeo <= 0)
			dev->watchdog_timeo = 5*HZ;
		if (!mod_timer(&dev->watchdog_timer,
			       round_jiffies(jiffies + dev->watchdog_timeo)))
			dev_hold(dev);
	}
}

static struct ip_tunnel * ipip6_tunnel_locate(struct net *net,
		struct ip_tunnel_parm *parms, int create)
{
	__be32 remote = parms->iph.daddr;
	__be32 local = parms->iph.saddr;
	struct ip_tunnel *t, **tp, *nt;
	struct net_device *dev;
	char name[IFNAMSIZ];
	struct sit_net *sitn = net_generic(net, sit_net_id);

	for (tp = __ipip6_bucket(sitn, parms); (t = *tp) != NULL; tp = &t->next) {
		if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr)
			return t;
	}
	if (!create)
		goto failed;

	if (parms->name[0])
		strlcpy(name, parms->name, IFNAMSIZ);
	else
		sprintf(name, "sit%%d");

	dev = alloc_netdev(sizeof(*t), name, ipip6_tunnel_setup);
	if (dev == NULL)
		return NULL;

	dev_net_set(dev, net);

	if (strchr(name, '%')) {
		if (dev_alloc_name(dev, name) < 0)
			goto failed_free;
	}

	nt = netdev_priv(dev);

	nt->parms = *parms;
	ipip6_tunnel_init(dev);
	ipip6_tunnel_clone_6rd(dev, sitn);

	if (parms->i_flags & SIT_ISATAP)
		dev->priv_flags |= IFF_ISATAP;

	if (register_netdevice(dev) < 0)
		goto failed_free;

	dev_hold(dev);

	ipip6_tunnel_link(sitn, nt);
	return nt;

failed_free:
	free_netdev(dev);
failed:
	return NULL;
}

int xfrm_dev_state_add(struct net *net, struct xfrm_state *x,
		       struct xfrm_user_offload *xuo)
{
	int err;
	struct dst_entry *dst;
	struct net_device *dev;
	struct xfrm_state_offload *xso = &x->xso;
	xfrm_address_t *saddr;
	xfrm_address_t *daddr;

	if (!x->type_offload)
		return -EINVAL;

	/* We don't yet support UDP encapsulation, TFC padding and ESN. */
	if (x->encap || x->tfcpad || (x->props.flags & XFRM_STATE_ESN))
		return 0;

	dev = dev_get_by_index(net, xuo->ifindex);
	if (!dev) {
		if (!(xuo->flags & XFRM_OFFLOAD_INBOUND)) {
			saddr = &x->props.saddr;
			daddr = &x->id.daddr;
		} else {
			saddr = &x->id.daddr;
			daddr = &x->props.saddr;
		}

		dst = __xfrm_dst_lookup(net, 0, 0, saddr, daddr,
					x->props.family, x->props.output_mark);
		if (IS_ERR(dst))
			return 0;

		dev = dst->dev;

		dev_hold(dev);
		dst_release(dst);
	}

	if (!dev->xfrmdev_ops || !dev->xfrmdev_ops->xdo_dev_state_add) {
		dev_put(dev);
		return 0;
	}

	xso->dev = dev;
	xso->num_exthdrs = 1;
	xso->flags = xuo->flags;

	err = dev->xfrmdev_ops->xdo_dev_state_add(x);
	if (err) {
		dev_put(dev);
		return err;
	}

	return 0;
}

static void ip6_fb_tnl_dev_init(struct net_device *dev)
{
	struct ip6_tnl *t = netdev_priv(dev);
	struct net *net = dev_net(dev);
	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

	ip6_tnl_dev_init_gen(dev);
	t->parms.proto = IPPROTO_IPV6;
	dev_hold(dev);
	ip6n->tnls_wc[0] = t;
}

static int pim6_rcv(struct sk_buff *skb)
{
	struct pimreghdr *pim;
	struct ipv6hdr   *encap;
	struct net_device  *reg_dev = NULL;

	if (!pskb_may_pull(skb, sizeof(*pim) + sizeof(*encap)))
		goto drop;

	pim = (struct pimreghdr *)skb_transport_header(skb);
	if (pim->type != ((PIM_VERSION << 4) | PIM_REGISTER) ||
	    (pim->flags & PIM_NULL_REGISTER) ||
	    (ip_compute_csum((void *)pim, sizeof(*pim)) != 0 &&
	     csum_fold(skb_checksum(skb, 0, skb->len, 0))))
		goto drop;

	/* check if the inner packet is destined to mcast group */
	encap = (struct ipv6hdr *)(skb_transport_header(skb) +
				   sizeof(*pim));

	if (!ipv6_addr_is_multicast(&encap->daddr) ||
	    encap->payload_len == 0 ||
	    ntohs(encap->payload_len) + sizeof(*pim) > skb->len)
		goto drop;

	read_lock(&mrt_lock);
	if (reg_vif_num >= 0)
		reg_dev = vif6_table[reg_vif_num].dev;
	if (reg_dev)
		dev_hold(reg_dev);
	read_unlock(&mrt_lock);

	if (reg_dev == NULL)
		goto drop;

	skb->mac_header = skb->network_header;
	skb_pull(skb, (u8 *)encap - skb->data);
	skb_reset_network_header(skb);
	skb->dev = reg_dev;
	skb->protocol = htons(ETH_P_IP);
	skb->ip_summed = 0;
	skb->pkt_type = PACKET_HOST;
	dst_release(skb->dst);
	((struct net_device_stats *)netdev_priv(reg_dev))->rx_bytes += skb->len;
	((struct net_device_stats *)netdev_priv(reg_dev))->rx_packets++;
	skb->dst = NULL;
	nf_reset(skb);
	netif_rx(skb);
	dev_put(reg_dev);
	return 0;
 drop:
	kfree_skb(skb);
	return 0;
}

static void linkwatch_add_event(struct net_device *dev)
{
	unsigned long flags;

	spin_lock_irqsave(&lweventlist_lock, flags);
	if (list_empty(&dev->link_watch_list)) {
		list_add_tail(&dev->link_watch_list, &lweventlist);
		dev_hold(dev);
	}
	spin_unlock_irqrestore(&lweventlist_lock, flags);
}

static struct net_device *rxe_get_netdev(struct ib_device *device,
					 u8 port_num)
{
	struct rxe_dev *rxe = to_rdev(device);

	if (rxe->ndev) {
		dev_hold(rxe->ndev);
		return rxe->ndev;
	}

	return NULL;
}

int register_vlan_dev(struct net_device *dev)
{
	struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
	struct net_device *real_dev = vlan->real_dev;
	u16 vlan_id = vlan->vlan_id;
	struct vlan_info *vlan_info;
	struct vlan_group *grp;
	int err;

	err = vlan_vid_add(real_dev, vlan_id);
	if (err)
		return err;

	vlan_info = rtnl_dereference(real_dev->vlan_info);
	/* vlan_info should be there now. vlan_vid_add took care of it */
	BUG_ON(!vlan_info);

	grp = &vlan_info->grp;
	if (grp->nr_vlan_devs == 0) {
		err = vlan_gvrp_init_applicant(real_dev);
		if (err < 0)
			goto out_vid_del;
	}

	err = vlan_group_prealloc_vid(grp, vlan_id);
	if (err < 0)
		goto out_uninit_applicant;

	err = register_netdevice(dev);
	if (err < 0)
		goto out_uninit_applicant;

	/* Account for reference in struct vlan_dev_priv */
	dev_hold(real_dev);

	netif_stacked_transfer_operstate(real_dev, dev);
	linkwatch_fire_event(dev); /* _MUST_ call rfc2863_policy() */

	/* So, got the sucker initialized, now lets place
	 * it into our local structure.
	 */
	vlan_group_set_device(grp, vlan_id, dev);
	grp->nr_vlan_devs++;

	return 0;

out_uninit_applicant:
	if (grp->nr_vlan_devs == 0)
		vlan_gvrp_uninit_applicant(real_dev);
out_vid_del:
	vlan_vid_del(real_dev, vlan_id);
	return err;
}