diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 1e4adae2bde00308533fb4e6ca3ca603684af00b..666cf364df86dffbab3cd2b7b1ea66e72d3ac7a8 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -318,9 +318,7 @@ igmp_scount(struct ip_mc_list *pmc, int type, int gdeleted, int sdeleted)
 	return scount;
 }
 
-#define igmp_skb_size(skb) (*(unsigned int *)((skb)->cb))
-
-static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
+static struct sk_buff *igmpv3_newpack(struct net_device *dev, unsigned int mtu)
 {
 	struct sk_buff *skb;
 	struct rtable *rt;
@@ -330,6 +328,7 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
 	struct flowi4 fl4;
 	int hlen = LL_RESERVED_SPACE(dev);
 	int tlen = dev->needed_tailroom;
+	unsigned int size = mtu;
 
 	while (1) {
 		skb = alloc_skb(size + hlen + tlen,
@@ -341,7 +340,6 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
 			return NULL;
 	}
 	skb->priority = TC_PRIO_CONTROL;
-	igmp_skb_size(skb) = size;
 
 	rt = ip_route_output_ports(net, &fl4, NULL, IGMPV3_ALL_MCR, 0,
 				   0, 0,
@@ -354,6 +352,8 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
 	skb_dst_set(skb, &rt->dst);
 	skb->dev = dev;
 
+	skb->reserved_tailroom = skb_end_offset(skb) -
+				 min(mtu, skb_end_offset(skb));
 	skb_reserve(skb, hlen);
 
 	skb_reset_network_header(skb);
@@ -423,8 +423,7 @@ static struct sk_buff *add_grhead(struct sk_buff *skb, struct ip_mc_list *pmc,
 	return skb;
 }
 
-#define AVAILABLE(skb) ((skb) ? ((skb)->dev ? igmp_skb_size(skb) - (skb)->len : \
-	skb_tailroom(skb)) : 0)
+#define AVAILABLE(skb)	((skb) ? skb_availroom(skb) : 0)
 
 static struct sk_buff *add_grec(struct sk_buff *skb, struct ip_mc_list *pmc,
 	int type, int gdeleted, int sdeleted)
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index e04f184b783a1c2141a94bf6d8aad6c2f1bc8233..5ce107c8aab3477ba20c281c5eb859c572e7347f 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1550,7 +1550,7 @@ static void ip6_mc_hdr(struct sock *sk, struct sk_buff *skb,
 	hdr->daddr = *daddr;
 }
 
-static struct sk_buff *mld_newpack(struct inet6_dev *idev, int size)
+static struct sk_buff *mld_newpack(struct inet6_dev *idev, unsigned int mtu)
 {
 	struct net_device *dev = idev->dev;
 	struct net *net = dev_net(dev);
@@ -1561,13 +1561,13 @@ static struct sk_buff *mld_newpack(struct inet6_dev *idev, int size)
 	const struct in6_addr *saddr;
 	int hlen = LL_RESERVED_SPACE(dev);
 	int tlen = dev->needed_tailroom;
+	unsigned int size = mtu + hlen + tlen;
 	int err;
 	u8 ra[8] = { IPPROTO_ICMPV6, 0,
 		     IPV6_TLV_ROUTERALERT, 2, 0, 0,
 		     IPV6_TLV_PADN, 0 };
 
 	/* we assume size > sizeof(ra) here */
-	size += hlen + tlen;
 	/* limit our allocations to order-0 page */
 	size = min_t(int, size, SKB_MAX_ORDER(0, 0));
 	skb = sock_alloc_send_skb(sk, size, 1, &err);
@@ -1576,6 +1576,8 @@ static struct sk_buff *mld_newpack(struct inet6_dev *idev, int size)
 		return NULL;
 
 	skb->priority = TC_PRIO_CONTROL;
+	skb->reserved_tailroom = skb_end_offset(skb) -
+				 min(mtu, skb_end_offset(skb));
 	skb_reserve(skb, hlen);
 
 	if (__ipv6_get_lladdr(idev, &addr_buf, IFA_F_TENTATIVE)) {
@@ -1690,8 +1692,7 @@ static struct sk_buff *add_grhead(struct sk_buff *skb, struct ifmcaddr6 *pmc,
 	return skb;
 }
 
-#define AVAILABLE(skb) ((skb) ? ((skb)->dev ? (skb)->dev->mtu - (skb)->len : \
-	skb_tailroom(skb)) : 0)
+#define AVAILABLE(skb)	((skb) ? skb_availroom(skb) : 0)
 
 static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
 	int type, int gdeleted, int sdeleted, int crsend)