ipv4: Don't do expensive useless work during inetdev destroy.

When an inetdev is destroyed, every address assigned to the interface
is removed.  And in this scenerio we do two pointless things which can
be very expensive if the number of assigned interfaces is large:

1) Address promotion.  We are deleting all addresses, so there is no
   point in doing this.

2) A full nf conntrack table purge for every address.  We only need to
   do this once, as is already caught by the existing
   masq_dev_notifier so masq_inet_event() can skip this.

Reported-by: Solar Designer <solar@openwall.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
			     struct nlmsghdr *nlh, struct fib_config *cfg)
{
	struct nlattr *attr;
	int err, remaining;
	struct rtmsg *rtm;

	err = nlmsg_validate(nlh, sizeof(*rtm), RTA_MAX, rtm_ipv4_policy);
	if (err < 0)
		goto errout;

	memset(cfg, 0, sizeof(*cfg));

	rtm = nlmsg_data(nlh);
	cfg->fc_dst_len = rtm->rtm_dst_len;
	cfg->fc_tos = rtm->rtm_tos;
	cfg->fc_table = rtm->rtm_table;
	cfg->fc_protocol = rtm->rtm_protocol;
	cfg->fc_scope = rtm->rtm_scope;
	cfg->fc_type = rtm->rtm_type;
	cfg->fc_flags = rtm->rtm_flags;
	cfg->fc_nlflags = nlh->nlmsg_flags;

	cfg->fc_nlinfo.portid = NETLINK_CB(skb).portid;
	cfg->fc_nlinfo.nlh = nlh;
	cfg->fc_nlinfo.nl_net = net;

	if (cfg->fc_type > RTN_MAX) {
		err = -EINVAL;
		goto errout;
	}

	nlmsg_for_each_attr(attr, nlh, sizeof(struct rtmsg), remaining) {
		switch (nla_type(attr)) {
		case RTA_DST:
			cfg->fc_dst = nla_get_be32(attr);
			break;
		case RTA_OIF:
			cfg->fc_oif = nla_get_u32(attr);
			break;
		case RTA_GATEWAY:
			cfg->fc_gw = nla_get_be32(attr);
			break;
		case RTA_PRIORITY:
			cfg->fc_priority = nla_get_u32(attr);
			break;
		case RTA_PREFSRC:
			cfg->fc_prefsrc = nla_get_be32(attr);
			break;
		case RTA_METRICS:
			cfg->fc_mx = nla_data(attr);
			cfg->fc_mx_len = nla_len(attr);
			break;
		case RTA_MULTIPATH:
			cfg->fc_mp = nla_data(attr);
			cfg->fc_mp_len = nla_len(attr);
			break;
		case RTA_FLOW:
			cfg->fc_flow = nla_get_u32(attr);
			break;
		case RTA_TABLE:
			cfg->fc_table = nla_get_u32(attr);
			break;
		case RTA_ENCAP:
			cfg->fc_encap = attr;
			break;
		case RTA_ENCAP_TYPE:
			cfg->fc_encap_type = nla_get_u16(attr);
			break;
		}
	}

	return 0;
errout:
	return err;
}

static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
			     struct nlmsghdr *nlh, struct fib_config *cfg)
{
	struct nlattr *attr;
	int err, remaining;
	struct rtmsg *rtm;

	err = nlmsg_validate(nlh, sizeof(*rtm), RTA_MAX, rtm_ipv4_policy);
	if (err < 0)
		goto errout;

	memset(cfg, 0, sizeof(*cfg));

	rtm = nlmsg_data(nlh);
	cfg->fc_dst_len = rtm->rtm_dst_len;
	cfg->fc_tos = rtm->rtm_tos;
	cfg->fc_table = rtm->rtm_table;
	cfg->fc_protocol = rtm->rtm_protocol;
	cfg->fc_scope = rtm->rtm_scope;
	cfg->fc_type = rtm->rtm_type;
	cfg->fc_flags = rtm->rtm_flags;
	cfg->fc_nlflags = nlh->nlmsg_flags;

	cfg->fc_nlinfo.portid = NETLINK_CB(skb).portid;
	cfg->fc_nlinfo.nlh = nlh;
	cfg->fc_nlinfo.nl_net = net;

	if (cfg->fc_type > RTN_MAX) {
		err = -EINVAL;
		goto errout;
	}

	nlmsg_for_each_attr(attr, nlh, sizeof(struct rtmsg), remaining) {
		switch (nla_type(attr)) {
		case RTA_DST:
			cfg->fc_dst = nla_get_be32(attr);
			break;
		case RTA_OIF:
			cfg->fc_oif = nla_get_u32(attr);
			break;
		case RTA_GATEWAY:
			cfg->fc_gw = nla_get_be32(attr);
			break;
		case RTA_PRIORITY:
			cfg->fc_priority = nla_get_u32(attr);
			break;
		case RTA_PREFSRC:
			cfg->fc_prefsrc = nla_get_be32(attr);
			break;
		case RTA_METRICS:
			cfg->fc_mx = nla_data(attr);
			cfg->fc_mx_len = nla_len(attr);
			break;
		case RTA_MULTIPATH:
			cfg->fc_mp = nla_data(attr);
			cfg->fc_mp_len = nla_len(attr);
			break;
		case RTA_FLOW:
			cfg->fc_flow = nla_get_u32(attr);
			break;
		case RTA_TABLE:
			cfg->fc_table = nla_get_u32(attr);
			break;
		case RTA_ENCAP:
			cfg->fc_encap = attr;
			break;
		case RTA_ENCAP_TYPE:
			cfg->fc_encap_type = nla_get_u16(attr);
			break;
		}
	}

	return 0;
errout:
	return err;
}
