Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1663 insertions, 0 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
new file mode 100644
index 0000000000..4ab877cf6d
--- /dev/null
+++ b/net/ipv4/ip_output.c
@@ -0,0 +1,1663 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		The Internet Protocol (IP) output module.
+ *
+ * Authors:	Ross Biro
+ *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
+ *		Donald Becker, <becker@super.org>
+ *		Alan Cox, <Alan.Cox@linux.org>
+ *		Richard Underwood
+ *		Stefan Becker, <stefanb@yello.ping.de>
+ *		Jorge Cwik, <jorge@laser.satlink.net>
+ *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
+ *		Hirokazu Takahashi, <taka@valinux.co.jp>
+ *
+ *	See ip_input.c for original log
+ *
+ *	Fixes:
+ *		Alan Cox	:	Missing nonblock feature in ip_build_xmit.
+ *		Mike Kilburn	:	htons() missing in ip_build_xmit.
+ *		Bradford Johnson:	Fix faulty handling of some frames when
+ *					no route is found.
+ *		Alexander Demenshin:	Missing sk/skb free in ip_queue_xmit
+ *					(in case if packet not accepted by
+ *					output firewall rules)
+ *		Mike McLagan	:	Routing by source
+ *		Alexey Kuznetsov:	use new route cache
+ *		Andi Kleen:		Fix broken PMTU recovery and remove
+ *					some redundant tests.
+ *	Vitaly E. Lavrov	:	Transparent proxy revived after year coma.
+ *		Andi Kleen	: 	Replace ip_reply with ip_send_reply.
+ *		Andi Kleen	:	Split fast and slow ip_build_xmit path
+ *					for decreased register pressure on x86
+ *					and more readability.
+ *		Marc Boucher	:	When call_out_firewall returns FW_QUEUE,
+ *					silently drop skb instead of failing with -EPERM.
+ *		Detlev Wengorz	:	Copy protocol for fragments.
+ *		Hirokazu Takahashi:	HW checksumming for outgoing UDP
+ *					datagrams.
+ *		Hirokazu Takahashi:	sendfile() on UDP works now.
+ */
+
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/slab.h>
+
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/in.h>
+#include <linux/inet.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/proc_fs.h>
+#include <linux/stat.h>
+#include <linux/init.h>
+
+#include <net/snmp.h>
+#include <net/ip.h>
+#include <net/protocol.h>
+#include <net/route.h>
+#include <net/xfrm.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/arp.h>
+#include <net/icmp.h>
+#include <net/checksum.h>
+#include <net/gso.h>
+#include <net/inetpeer.h>
+#include <net/inet_ecn.h>
+#include <net/lwtunnel.h>
+#include <linux/bpf-cgroup.h>
+#include <linux/igmp.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_bridge.h>
+#include <linux/netlink.h>
+#include <linux/tcp.h>
+
+static int
+ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
+	    unsigned int mtu,
+	    int (*output)(struct net *, struct sock *, struct sk_buff *));
+
+/* Generate a checksum for an outgoing IP datagram. */
+void ip_send_check(struct iphdr *iph)
+{
+	iph->check = 0;
+	iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
+}
+EXPORT_SYMBOL(ip_send_check);
+
+int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	struct iphdr *iph = ip_hdr(skb);
+
+	iph_set_totlen(iph, skb->len);
+	ip_send_check(iph);
+
+	/* if egress device is enslaved to an L3 master device pass the
+	 * skb to its handler for processing
+	 */
+	skb = l3mdev_ip_out(sk, skb);
+	if (unlikely(!skb))
+		return 0;
+
+	skb->protocol = htons(ETH_P_IP);
+
+	return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
+		       net, sk, skb, NULL, skb_dst(skb)->dev,
+		       dst_output);
+}
+
+int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	int err;
+
+	err = __ip_local_out(net, sk, skb);
+	if (likely(err == 1))
+		err = dst_output(net, sk, skb);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(ip_local_out);
+
+static inline int ip_select_ttl(const struct inet_sock *inet,
+				const struct dst_entry *dst)
+{
+	int ttl = READ_ONCE(inet->uc_ttl);
+
+	if (ttl < 0)
+		ttl = ip4_dst_hoplimit(dst);
+	return ttl;
+}
+
+/*
+ *		Add an ip header to a skbuff and send it out.
+ *
+ */
+int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
+			  __be32 saddr, __be32 daddr, struct ip_options_rcu *opt,
+			  u8 tos)
+{
+	const struct inet_sock *inet = inet_sk(sk);
+	struct rtable *rt = skb_rtable(skb);
+	struct net *net = sock_net(sk);
+	struct iphdr *iph;
+
+	/* Build the IP header. */
+	skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
+	skb_reset_network_header(skb);
+	iph = ip_hdr(skb);
+	iph->version  = 4;
+	iph->ihl      = 5;
+	iph->tos      = tos;
+	iph->ttl      = ip_select_ttl(inet, &rt->dst);
+	iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
+	iph->saddr    = saddr;
+	iph->protocol = sk->sk_protocol;
+	/* Do not bother generating IPID for small packets (eg SYNACK) */
+	if (skb->len <= IPV4_MIN_MTU || ip_dont_fragment(sk, &rt->dst)) {
+		iph->frag_off = htons(IP_DF);
+		iph->id = 0;
+	} else {
+		iph->frag_off = 0;
+		/* TCP packets here are SYNACK with fat IPv4/TCP options.
+		 * Avoid using the hashed IP ident generator.
+		 */
+		if (sk->sk_protocol == IPPROTO_TCP)
+			iph->id = (__force __be16)get_random_u16();
+		else
+			__ip_select_ident(net, iph, 1);
+	}
+
+	if (opt && opt->opt.optlen) {
+		iph->ihl += opt->opt.optlen>>2;
+		ip_options_build(skb, &opt->opt, daddr, rt);
+	}
+
+	skb->priority = READ_ONCE(sk->sk_priority);
+	if (!skb->mark)
+		skb->mark = READ_ONCE(sk->sk_mark);
+
+	/* Send it out. */
+	return ip_local_out(net, skb->sk, skb);
+}
+EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
+
+static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	struct rtable *rt = (struct rtable *)dst;
+	struct net_device *dev = dst->dev;
+	unsigned int hh_len = LL_RESERVED_SPACE(dev);
+	struct neighbour *neigh;
+	bool is_v6gw = false;
+
+	if (rt->rt_type == RTN_MULTICAST) {
+		IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
+	} else if (rt->rt_type == RTN_BROADCAST)
+		IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
+
+	/* OUTOCTETS should be counted after fragment */
+	IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
+
+	if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
+		skb = skb_expand_head(skb, hh_len);
+		if (!skb)
+			return -ENOMEM;
+	}
+
+	if (lwtunnel_xmit_redirect(dst->lwtstate)) {
+		int res = lwtunnel_xmit(skb);
+
+		if (res != LWTUNNEL_XMIT_CONTINUE)
+			return res;
+	}
+
+	rcu_read_lock();
+	neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
+	if (!IS_ERR(neigh)) {
+		int res;
+
+		sock_confirm_neigh(skb, neigh);
+		/* if crossing protocols, can not use the cached header */
+		res = neigh_output(neigh, skb, is_v6gw);
+		rcu_read_unlock();
+		return res;
+	}
+	rcu_read_unlock();
+
+	net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
+			    __func__);
+	kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_CREATEFAIL);
+	return PTR_ERR(neigh);
+}
+
+static int ip_finish_output_gso(struct net *net, struct sock *sk,
+				struct sk_buff *skb, unsigned int mtu)
+{
+	struct sk_buff *segs, *nskb;
+	netdev_features_t features;
+	int ret = 0;
+
+	/* common case: seglen is <= mtu
+	 */
+	if (skb_gso_validate_network_len(skb, mtu))
+		return ip_finish_output2(net, sk, skb);
+
+	/* Slowpath -  GSO segment length exceeds the egress MTU.
+	 *
+	 * This can happen in several cases:
+	 *  - Forwarding of a TCP GRO skb, when DF flag is not set.
+	 *  - Forwarding of an skb that arrived on a virtualization interface
+	 *    (virtio-net/vhost/tap) with TSO/GSO size set by other network
+	 *    stack.
+	 *  - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
+	 *    interface with a smaller MTU.
+	 *  - Arriving GRO skb (or GSO skb in a virtualized environment) that is
+	 *    bridged to a NETIF_F_TSO tunnel stacked over an interface with an
+	 *    insufficient MTU.
+	 */
+	features = netif_skb_features(skb);
+	BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_GSO_CB_OFFSET);
+	segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
+	if (IS_ERR_OR_NULL(segs)) {
+		kfree_skb(skb);
+		return -ENOMEM;
+	}
+
+	consume_skb(skb);
+
+	skb_list_walk_safe(segs, segs, nskb) {
+		int err;
+
+		skb_mark_not_on_list(segs);
+		err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
+
+		if (err && ret == 0)
+			ret = err;
+	}
+
+	return ret;
+}
+
+static int __ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	unsigned int mtu;
+
+#if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
+	/* Policy lookup after SNAT yielded a new policy */
+	if (skb_dst(skb)->xfrm) {
+		IPCB(skb)->flags |= IPSKB_REROUTED;
+		return dst_output(net, sk, skb);
+	}
+#endif
+	mtu = ip_skb_dst_mtu(sk, skb);
+	if (skb_is_gso(skb))
+		return ip_finish_output_gso(net, sk, skb, mtu);
+
+	if (skb->len > mtu || IPCB(skb)->frag_max_size)
+		return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
+
+	return ip_finish_output2(net, sk, skb);
+}
+
+static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	int ret;
+
+	ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
+	switch (ret) {
+	case NET_XMIT_SUCCESS:
+		return __ip_finish_output(net, sk, skb);
+	case NET_XMIT_CN:
+		return __ip_finish_output(net, sk, skb) ? : ret;
+	default:
+		kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS);
+		return ret;
+	}
+}
+
+static int ip_mc_finish_output(struct net *net, struct sock *sk,
+			       struct sk_buff *skb)
+{
+	struct rtable *new_rt;
+	bool do_cn = false;
+	int ret, err;
+
+	ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
+	switch (ret) {
+	case NET_XMIT_CN:
+		do_cn = true;
+		fallthrough;
+	case NET_XMIT_SUCCESS:
+		break;
+	default:
+		kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS);
+		return ret;
+	}
+
+	/* Reset rt_iif so that inet_iif() will return skb->skb_iif. Setting
+	 * this to non-zero causes ipi_ifindex in in_pktinfo to be overwritten,
+	 * see ipv4_pktinfo_prepare().
+	 */
+	new_rt = rt_dst_clone(net->loopback_dev, skb_rtable(skb));
+	if (new_rt) {
+		new_rt->rt_iif = 0;
+		skb_dst_drop(skb);
+		skb_dst_set(skb, &new_rt->dst);
+	}
+
+	err = dev_loopback_xmit(net, sk, skb);
+	return (do_cn && err) ? ret : err;
+}
+
+int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	struct rtable *rt = skb_rtable(skb);
+	struct net_device *dev = rt->dst.dev;
+
+	/*
+	 *	If the indicated interface is up and running, send the packet.
+	 */
+	skb->dev = dev;
+	skb->protocol = htons(ETH_P_IP);
+
+	/*
+	 *	Multicasts are looped back for other local users
+	 */
+
+	if (rt->rt_flags&RTCF_MULTICAST) {
+		if (sk_mc_loop(sk)
+#ifdef CONFIG_IP_MROUTE
+		/* Small optimization: do not loopback not local frames,
+		   which returned after forwarding; they will be  dropped
+		   by ip_mr_input in any case.
+		   Note, that local frames are looped back to be delivered
+		   to local recipients.
+
+		   This check is duplicated in ip_mr_input at the moment.
+		 */
+		    &&
+		    ((rt->rt_flags & RTCF_LOCAL) ||
+		     !(IPCB(skb)->flags & IPSKB_FORWARDED))
+#endif
+		   ) {
+			struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
+			if (newskb)
+				NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
+					net, sk, newskb, NULL, newskb->dev,
+					ip_mc_finish_output);
+		}
+
+		/* Multicasts with ttl 0 must not go beyond the host */
+
+		if (ip_hdr(skb)->ttl == 0) {
+			kfree_skb(skb);
+			return 0;
+		}
+	}
+
+	if (rt->rt_flags&RTCF_BROADCAST) {
+		struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
+		if (newskb)
+			NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
+				net, sk, newskb, NULL, newskb->dev,
+				ip_mc_finish_output);
+	}
+
+	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
+			    net, sk, skb, NULL, skb->dev,
+			    ip_finish_output,
+			    !(IPCB(skb)->flags & IPSKB_REROUTED));
+}
+
+int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	struct net_device *dev = skb_dst(skb)->dev, *indev = skb->dev;
+
+	skb->dev = dev;
+	skb->protocol = htons(ETH_P_IP);
+
+	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
+			    net, sk, skb, indev, dev,
+			    ip_finish_output,
+			    !(IPCB(skb)->flags & IPSKB_REROUTED));
+}
+EXPORT_SYMBOL(ip_output);
+
+/*
+ * copy saddr and daddr, possibly using 64bit load/stores
+ * Equivalent to :
+ *   iph->saddr = fl4->saddr;
+ *   iph->daddr = fl4->daddr;
+ */
+static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
+{
+	BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
+		     offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
+
+	iph->saddr = fl4->saddr;
+	iph->daddr = fl4->daddr;
+}
+
+/* Note: skb->sk can be different from sk, in case of tunnels */
+int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
+		    __u8 tos)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct net *net = sock_net(sk);
+	struct ip_options_rcu *inet_opt;
+	struct flowi4 *fl4;
+	struct rtable *rt;
+	struct iphdr *iph;
+	int res;
+
+	/* Skip all of this if the packet is already routed,
+	 * f.e. by something like SCTP.
+	 */
+	rcu_read_lock();
+	inet_opt = rcu_dereference(inet->inet_opt);
+	fl4 = &fl->u.ip4;
+	rt = skb_rtable(skb);
+	if (rt)
+		goto packet_routed;
+
+	/* Make sure we can route this packet. */
+	rt = (struct rtable *)__sk_dst_check(sk, 0);
+	if (!rt) {
+		__be32 daddr;
+
+		/* Use correct destination address if we have options. */
+		daddr = inet->inet_daddr;
+		if (inet_opt && inet_opt->opt.srr)
+			daddr = inet_opt->opt.faddr;
+
+		/* If this fails, retransmit mechanism of transport layer will
+		 * keep trying until route appears or the connection times
+		 * itself out.
+		 */
+		rt = ip_route_output_ports(net, fl4, sk,
+					   daddr, inet->inet_saddr,
+					   inet->inet_dport,
+					   inet->inet_sport,
+					   sk->sk_protocol,
+					   RT_CONN_FLAGS_TOS(sk, tos),
+					   sk->sk_bound_dev_if);
+		if (IS_ERR(rt))
+			goto no_route;
+		sk_setup_caps(sk, &rt->dst);
+	}
+	skb_dst_set_noref(skb, &rt->dst);
+
+packet_routed:
+	if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
+		goto no_route;
+
+	/* OK, we know where to send it, allocate and build IP header. */
+	skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
+	skb_reset_network_header(skb);
+	iph = ip_hdr(skb);
+	*((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (tos & 0xff));
+	if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
+		iph->frag_off = htons(IP_DF);
+	else
+		iph->frag_off = 0;
+	iph->ttl      = ip_select_ttl(inet, &rt->dst);
+	iph->protocol = sk->sk_protocol;
+	ip_copy_addrs(iph, fl4);
+
+	/* Transport layer set skb->h.foo itself. */
+
+	if (inet_opt && inet_opt->opt.optlen) {
+		iph->ihl += inet_opt->opt.optlen >> 2;
+		ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt);
+	}
+
+	ip_select_ident_segs(net, skb, sk,
+			     skb_shinfo(skb)->gso_segs ?: 1);
+
+	/* TODO : should we use skb->sk here instead of sk ? */
+	skb->priority = READ_ONCE(sk->sk_priority);
+	skb->mark = READ_ONCE(sk->sk_mark);
+
+	res = ip_local_out(net, sk, skb);
+	rcu_read_unlock();
+	return res;
+
+no_route:
+	rcu_read_unlock();
+	IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
+	kfree_skb_reason(skb, SKB_DROP_REASON_IP_OUTNOROUTES);
+	return -EHOSTUNREACH;
+}
+EXPORT_SYMBOL(__ip_queue_xmit);
+
+int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
+{
+	return __ip_queue_xmit(sk, skb, fl, inet_sk(sk)->tos);
+}
+EXPORT_SYMBOL(ip_queue_xmit);
+
+static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
+{
+	to->pkt_type = from->pkt_type;
+	to->priority = from->priority;
+	to->protocol = from->protocol;
+	to->skb_iif = from->skb_iif;
+	skb_dst_drop(to);
+	skb_dst_copy(to, from);
+	to->dev = from->dev;
+	to->mark = from->mark;
+
+	skb_copy_hash(to, from);
+
+#ifdef CONFIG_NET_SCHED
+	to->tc_index = from->tc_index;
+#endif
+	nf_copy(to, from);
+	skb_ext_copy(to, from);
+#if IS_ENABLED(CONFIG_IP_VS)
+	to->ipvs_property = from->ipvs_property;
+#endif
+	skb_copy_secmark(to, from);
+}
+
+static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
+		       unsigned int mtu,
+		       int (*output)(struct net *, struct sock *, struct sk_buff *))
+{
+	struct iphdr *iph = ip_hdr(skb);
+
+	if ((iph->frag_off & htons(IP_DF)) == 0)
+		return ip_do_fragment(net, sk, skb, output);
+
+	if (unlikely(!skb->ignore_df ||
+		     (IPCB(skb)->frag_max_size &&
+		      IPCB(skb)->frag_max_size > mtu))) {
+		IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
+		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
+			  htonl(mtu));
+		kfree_skb(skb);
+		return -EMSGSIZE;
+	}
+
+	return ip_do_fragment(net, sk, skb, output);
+}
+
+void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph,
+		      unsigned int hlen, struct ip_fraglist_iter *iter)
+{
+	unsigned int first_len = skb_pagelen(skb);
+
+	iter->frag = skb_shinfo(skb)->frag_list;
+	skb_frag_list_init(skb);
+
+	iter->offset = 0;
+	iter->iph = iph;
+	iter->hlen = hlen;
+
+	skb->data_len = first_len - skb_headlen(skb);
+	skb->len = first_len;
+	iph->tot_len = htons(first_len);
+	iph->frag_off = htons(IP_MF);
+	ip_send_check(iph);
+}
+EXPORT_SYMBOL(ip_fraglist_init);
+
+void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter)
+{
+	unsigned int hlen = iter->hlen;
+	struct iphdr *iph = iter->iph;
+	struct sk_buff *frag;
+
+	frag = iter->frag;
+	frag->ip_summed = CHECKSUM_NONE;
+	skb_reset_transport_header(frag);
+	__skb_push(frag, hlen);
+	skb_reset_network_header(frag);
+	memcpy(skb_network_header(frag), iph, hlen);
+	iter->iph = ip_hdr(frag);
+	iph = iter->iph;
+	iph->tot_len = htons(frag->len);
+	ip_copy_metadata(frag, skb);
+	iter->offset += skb->len - hlen;
+	iph->frag_off = htons(iter->offset >> 3);
+	if (frag->next)
+		iph->frag_off |= htons(IP_MF);
+	/* Ready, complete checksum */
+	ip_send_check(iph);
+}
+EXPORT_SYMBOL(ip_fraglist_prepare);
+
+void ip_frag_init(struct sk_buff *skb, unsigned int hlen,
+		  unsigned int ll_rs, unsigned int mtu, bool DF,
+		  struct ip_frag_state *state)
+{
+	struct iphdr *iph = ip_hdr(skb);
+
+	state->DF = DF;
+	state->hlen = hlen;
+	state->ll_rs = ll_rs;
+	state->mtu = mtu;
+
+	state->left = skb->len - hlen;	/* Space per frame */
+	state->ptr = hlen;		/* Where to start from */
+
+	state->offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
+	state->not_last_frag = iph->frag_off & htons(IP_MF);
+}
+EXPORT_SYMBOL(ip_frag_init);
+
+static void ip_frag_ipcb(struct sk_buff *from, struct sk_buff *to,
+			 bool first_frag)
+{
+	/* Copy the flags to each fragment. */
+	IPCB(to)->flags = IPCB(from)->flags;
+
+	/* ANK: dirty, but effective trick. Upgrade options only if
+	 * the segment to be fragmented was THE FIRST (otherwise,
+	 * options are already fixed) and make it ONCE
+	 * on the initial skb, so that all the following fragments
+	 * will inherit fixed options.
+	 */
+	if (first_frag)
+		ip_options_fragment(from);
+}
+
+struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state)
+{
+	unsigned int len = state->left;
+	struct sk_buff *skb2;
+	struct iphdr *iph;
+
+	/* IF: it doesn't fit, use 'mtu' - the data space left */
+	if (len > state->mtu)
+		len = state->mtu;
+	/* IF: we are not sending up to and including the packet end
+	   then align the next start on an eight byte boundary */
+	if (len < state->left)	{
+		len &= ~7;
+	}
+
+	/* Allocate buffer */
+	skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC);
+	if (!skb2)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 *	Set up data on packet
+	 */
+
+	ip_copy_metadata(skb2, skb);
+	skb_reserve(skb2, state->ll_rs);
+	skb_put(skb2, len + state->hlen);
+	skb_reset_network_header(skb2);
+	skb2->transport_header = skb2->network_header + state->hlen;
+
+	/*
+	 *	Charge the memory for the fragment to any owner
+	 *	it might possess
+	 */
+
+	if (skb->sk)
+		skb_set_owner_w(skb2, skb->sk);
+
+	/*
+	 *	Copy the packet header into the new buffer.
+	 */
+
+	skb_copy_from_linear_data(skb, skb_network_header(skb2), state->hlen);
+
+	/*
+	 *	Copy a block of the IP datagram.
+	 */
+	if (skb_copy_bits(skb, state->ptr, skb_transport_header(skb2), len))
+		BUG();
+	state->left -= len;
+
+	/*
+	 *	Fill in the new header fields.
+	 */
+	iph = ip_hdr(skb2);
+	iph->frag_off = htons((state->offset >> 3));
+	if (state->DF)
+		iph->frag_off |= htons(IP_DF);
+
+	/*
+	 *	Added AC : If we are fragmenting a fragment that's not the
+	 *		   last fragment then keep MF on each bit
+	 */
+	if (state->left > 0 || state->not_last_frag)
+		iph->frag_off |= htons(IP_MF);
+	state->ptr += len;
+	state->offset += len;
+
+	iph->tot_len = htons(len + state->hlen);
+
+	ip_send_check(iph);
+
+	return skb2;
+}
+EXPORT_SYMBOL(ip_frag_next);
+
+/*
+ *	This IP datagram is too large to be sent in one piece.  Break it up into
+ *	smaller pieces (each of size equal to IP header plus
+ *	a block of the data of the original IP data part) that will yet fit in a
+ *	single device frame, and queue such a frame for sending.
+ */
+
+int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
+		   int (*output)(struct net *, struct sock *, struct sk_buff *))
+{
+	struct iphdr *iph;
+	struct sk_buff *skb2;
+	bool mono_delivery_time = skb->mono_delivery_time;
+	struct rtable *rt = skb_rtable(skb);
+	unsigned int mtu, hlen, ll_rs;
+	struct ip_fraglist_iter iter;
+	ktime_t tstamp = skb->tstamp;
+	struct ip_frag_state state;
+	int err = 0;
+
+	/* for offloaded checksums cleanup checksum before fragmentation */
+	if (skb->ip_summed == CHECKSUM_PARTIAL &&
+	    (err = skb_checksum_help(skb)))
+		goto fail;
+
+	/*
+	 *	Point into the IP datagram header.
+	 */
+
+	iph = ip_hdr(skb);
+
+	mtu = ip_skb_dst_mtu(sk, skb);
+	if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
+		mtu = IPCB(skb)->frag_max_size;
+
+	/*
+	 *	Setup starting values.
+	 */
+
+	hlen = iph->ihl * 4;
+	mtu = mtu - hlen;	/* Size of data space */
+	IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
+	ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
+
+	/* When frag_list is given, use it. First, check its validity:
+	 * some transformers could create wrong frag_list or break existing
+	 * one, it is not prohibited. In this case fall back to copying.
+	 *
+	 * LATER: this step can be merged to real generation of fragments,
+	 * we can switch to copy when see the first bad fragment.
+	 */
+	if (skb_has_frag_list(skb)) {
+		struct sk_buff *frag, *frag2;
+		unsigned int first_len = skb_pagelen(skb);
+
+		if (first_len - hlen > mtu ||
+		    ((first_len - hlen) & 7) ||
+		    ip_is_fragment(iph) ||
+		    skb_cloned(skb) ||
+		    skb_headroom(skb) < ll_rs)
+			goto slow_path;
+
+		skb_walk_frags(skb, frag) {
+			/* Correct geometry. */
+			if (frag->len > mtu ||
+			    ((frag->len & 7) && frag->next) ||
+			    skb_headroom(frag) < hlen + ll_rs)
+				goto slow_path_clean;
+
+			/* Partially cloned skb? */
+			if (skb_shared(frag))
+				goto slow_path_clean;
+
+			BUG_ON(frag->sk);
+			if (skb->sk) {
+				frag->sk = skb->sk;
+				frag->destructor = sock_wfree;
+			}
+			skb->truesize -= frag->truesize;
+		}
+
+		/* Everything is OK. Generate! */
+		ip_fraglist_init(skb, iph, hlen, &iter);
+
+		for (;;) {
+			/* Prepare header of the next frame,
+			 * before previous one went down. */
+			if (iter.frag) {
+				bool first_frag = (iter.offset == 0);
+
+				IPCB(iter.frag)->flags = IPCB(skb)->flags;
+				ip_fraglist_prepare(skb, &iter);
+				if (first_frag && IPCB(skb)->opt.optlen) {
+					/* ipcb->opt is not populated for frags
+					 * coming from __ip_make_skb(),
+					 * ip_options_fragment() needs optlen
+					 */
+					IPCB(iter.frag)->opt.optlen =
+						IPCB(skb)->opt.optlen;
+					ip_options_fragment(iter.frag);
+					ip_send_check(iter.iph);
+				}
+			}
+
+			skb_set_delivery_time(skb, tstamp, mono_delivery_time);
+			err = output(net, sk, skb);
+
+			if (!err)
+				IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
+			if (err || !iter.frag)
+				break;
+
+			skb = ip_fraglist_next(&iter);
+		}
+
+		if (err == 0) {
+			IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
+			return 0;
+		}
+
+		kfree_skb_list(iter.frag);
+
+		IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
+		return err;
+
+slow_path_clean:
+		skb_walk_frags(skb, frag2) {
+			if (frag2 == frag)
+				break;
+			frag2->sk = NULL;
+			frag2->destructor = NULL;
+			skb->truesize += frag2->truesize;
+		}
+	}
+
+slow_path:
+	/*
+	 *	Fragment the datagram.
+	 */
+
+	ip_frag_init(skb, hlen, ll_rs, mtu, IPCB(skb)->flags & IPSKB_FRAG_PMTU,
+		     &state);
+
+	/*
+	 *	Keep copying data until we run out.
+	 */
+
+	while (state.left > 0) {
+		bool first_frag = (state.offset == 0);
+
+		skb2 = ip_frag_next(skb, &state);
+		if (IS_ERR(skb2)) {
+			err = PTR_ERR(skb2);
+			goto fail;
+		}
+		ip_frag_ipcb(skb, skb2, first_frag);
+
+		/*
+		 *	Put this fragment into the sending queue.
+		 */
+		skb_set_delivery_time(skb2, tstamp, mono_delivery_time);
+		err = output(net, sk, skb2);
+		if (err)
+			goto fail;
+
+		IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
+	}
+	consume_skb(skb);
+	IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
+	return err;
+
+fail:
+	kfree_skb(skb);
+	IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
+	return err;
+}
+EXPORT_SYMBOL(ip_do_fragment);
+
+int
+ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
+{
+	struct msghdr *msg = from;
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		if (!copy_from_iter_full(to, len, &msg->msg_iter))
+			return -EFAULT;
+	} else {
+		__wsum csum = 0;
+		if (!csum_and_copy_from_iter_full(to, len, &csum, &msg->msg_iter))
+			return -EFAULT;
+		skb->csum = csum_block_add(skb->csum, csum, odd);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(ip_generic_getfrag);
+
+static int __ip_append_data(struct sock *sk,
+			    struct flowi4 *fl4,
+			    struct sk_buff_head *queue,
+			    struct inet_cork *cork,
+			    struct page_frag *pfrag,
+			    int getfrag(void *from, char *to, int offset,
+					int len, int odd, struct sk_buff *skb),
+			    void *from, int length, int transhdrlen,
+			    unsigned int flags)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct ubuf_info *uarg = NULL;
+	struct sk_buff *skb;
+	struct ip_options *opt = cork->opt;
+	int hh_len;
+	int exthdrlen;
+	int mtu;
+	int copy;
+	int err;
+	int offset = 0;
+	bool zc = false;
+	unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
+	int csummode = CHECKSUM_NONE;
+	struct rtable *rt = (struct rtable *)cork->dst;
+	unsigned int wmem_alloc_delta = 0;
+	bool paged, extra_uref = false;
+	u32 tskey = 0;
+
+	skb = skb_peek_tail(queue);
+
+	exthdrlen = !skb ? rt->dst.header_len : 0;
+	mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
+	paged = !!cork->gso_size;
+
+	if (cork->tx_flags & SKBTX_ANY_TSTAMP &&
+	    READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_OPT_ID)
+		tskey = atomic_inc_return(&sk->sk_tskey) - 1;
+
+	hh_len = LL_RESERVED_SPACE(rt->dst.dev);
+
+	fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
+	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
+	maxnonfragsize = ip_sk_ignore_df(sk) ? IP_MAX_MTU : mtu;
+
+	if (cork->length + length > maxnonfragsize - fragheaderlen) {
+		ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
+			       mtu - (opt ? opt->optlen : 0));
+		return -EMSGSIZE;
+	}
+
+	/*
+	 * transhdrlen > 0 means that this is the first fragment and we wish
+	 * it won't be fragmented in the future.
+	 */
+	if (transhdrlen &&
+	    length + fragheaderlen <= mtu &&
+	    rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) &&
+	    (!(flags & MSG_MORE) || cork->gso_size) &&
+	    (!exthdrlen || (rt->dst.dev->features & NETIF_F_HW_ESP_TX_CSUM)))
+		csummode = CHECKSUM_PARTIAL;
+
+	if ((flags & MSG_ZEROCOPY) && length) {
+		struct msghdr *msg = from;
+
+		if (getfrag == ip_generic_getfrag && msg->msg_ubuf) {
+			if (skb_zcopy(skb) && msg->msg_ubuf != skb_zcopy(skb))
+				return -EINVAL;
+
+			/* Leave uarg NULL if can't zerocopy, callers should
+			 * be able to handle it.
+			 */
+			if ((rt->dst.dev->features & NETIF_F_SG) &&
+			    csummode == CHECKSUM_PARTIAL) {
+				paged = true;
+				zc = true;
+				uarg = msg->msg_ubuf;
+			}
+		} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
+			uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
+			if (!uarg)
+				return -ENOBUFS;
+			extra_uref = !skb_zcopy(skb);	/* only ref on new uarg */
+			if (rt->dst.dev->features & NETIF_F_SG &&
+			    csummode == CHECKSUM_PARTIAL) {
+				paged = true;
+				zc = true;
+			} else {
+				uarg_to_msgzc(uarg)->zerocopy = 0;
+				skb_zcopy_set(skb, uarg, &extra_uref);
+			}
+		}
+	} else if ((flags & MSG_SPLICE_PAGES) && length) {
+		if (inet_test_bit(HDRINCL, sk))
+			return -EPERM;
+		if (rt->dst.dev->features & NETIF_F_SG &&
+		    getfrag == ip_generic_getfrag)
+			/* We need an empty buffer to attach stuff to */
+			paged = true;
+		else
+			flags &= ~MSG_SPLICE_PAGES;
+	}
+
+	cork->length += length;
+
+	/* So, what's going on in the loop below?
+	 *
+	 * We use calculated fragment length to generate chained skb,
+	 * each of segments is IP fragment ready for sending to network after
+	 * adding appropriate IP header.
+	 */
+
+	if (!skb)
+		goto alloc_new_skb;
+
+	while (length > 0) {
+		/* Check if the remaining data fits into current packet. */
+		copy = mtu - skb->len;
+		if (copy < length)
+			copy = maxfraglen - skb->len;
+		if (copy <= 0) {
+			char *data;
+			unsigned int datalen;
+			unsigned int fraglen;
+			unsigned int fraggap;
+			unsigned int alloclen, alloc_extra;
+			unsigned int pagedlen;
+			struct sk_buff *skb_prev;
+alloc_new_skb:
+			skb_prev = skb;
+			if (skb_prev)
+				fraggap = skb_prev->len - maxfraglen;
+			else
+				fraggap = 0;
+
+			/*
+			 * If remaining data exceeds the mtu,
+			 * we know we need more fragment(s).
+			 */
+			datalen = length + fraggap;
+			if (datalen > mtu - fragheaderlen)
+				datalen = maxfraglen - fragheaderlen;
+			fraglen = datalen + fragheaderlen;
+			pagedlen = 0;
+
+			alloc_extra = hh_len + 15;
+			alloc_extra += exthdrlen;
+
+			/* The last fragment gets additional space at tail.
+			 * Note, with MSG_MORE we overallocate on fragments,
+			 * because we have no idea what fragment will be
+			 * the last.
+			 */
+			if (datalen == length + fraggap)
+				alloc_extra += rt->dst.trailer_len;
+
+			if ((flags & MSG_MORE) &&
+			    !(rt->dst.dev->features&NETIF_F_SG))
+				alloclen = mtu;
+			else if (!paged &&
+				 (fraglen + alloc_extra < SKB_MAX_ALLOC ||
+				  !(rt->dst.dev->features & NETIF_F_SG)))
+				alloclen = fraglen;
+			else {
+				alloclen = fragheaderlen + transhdrlen;
+				pagedlen = datalen - transhdrlen;
+			}
+
+			alloclen += alloc_extra;
+
+			if (transhdrlen) {
+				skb = sock_alloc_send_skb(sk, alloclen,
+						(flags & MSG_DONTWAIT), &err);
+			} else {
+				skb = NULL;
+				if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <=
+				    2 * sk->sk_sndbuf)
+					skb = alloc_skb(alloclen,
+							sk->sk_allocation);
+				if (unlikely(!skb))
+					err = -ENOBUFS;
+			}
+			if (!skb)
+				goto error;
+
+			/*
+			 *	Fill in the control structures
+			 */
+			skb->ip_summed = csummode;
+			skb->csum = 0;
+			skb_reserve(skb, hh_len);
+
+			/*
+			 *	Find where to start putting bytes.
+			 */
+			data = skb_put(skb, fraglen + exthdrlen - pagedlen);
+			skb_set_network_header(skb, exthdrlen);
+			skb->transport_header = (skb->network_header +
+						 fragheaderlen);
+			data += fragheaderlen + exthdrlen;
+
+			if (fraggap) {
+				skb->csum = skb_copy_and_csum_bits(
+					skb_prev, maxfraglen,
+					data + transhdrlen, fraggap);
+				skb_prev->csum = csum_sub(skb_prev->csum,
+							  skb->csum);
+				data += fraggap;
+				pskb_trim_unique(skb_prev, maxfraglen);
+			}
+
+			copy = datalen - transhdrlen - fraggap - pagedlen;
+			/* [!] NOTE: copy will be negative if pagedlen>0
+			 * because then the equation reduces to -fraggap.
+			 */
+			if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
+				err = -EFAULT;
+				kfree_skb(skb);
+				goto error;
+			} else if (flags & MSG_SPLICE_PAGES) {
+				copy = 0;
+			}
+
+			offset += copy;
+			length -= copy + transhdrlen;
+			transhdrlen = 0;
+			exthdrlen = 0;
+			csummode = CHECKSUM_NONE;
+
+			/* only the initial fragment is time stamped */
+			skb_shinfo(skb)->tx_flags = cork->tx_flags;
+			cork->tx_flags = 0;
+			skb_shinfo(skb)->tskey = tskey;
+			tskey = 0;
+			skb_zcopy_set(skb, uarg, &extra_uref);
+
+			if ((flags & MSG_CONFIRM) && !skb_prev)
+				skb_set_dst_pending_confirm(skb, 1);
+
+			/*
+			 * Put the packet on the pending queue.
+			 */
+			if (!skb->destructor) {
+				skb->destructor = sock_wfree;
+				skb->sk = sk;
+				wmem_alloc_delta += skb->truesize;
+			}
+			__skb_queue_tail(queue, skb);
+			continue;
+		}
+
+		if (copy > length)
+			copy = length;
+
+		if (!(rt->dst.dev->features&NETIF_F_SG) &&
+		    skb_tailroom(skb) >= copy) {
+			unsigned int off;
+
+			off = skb->len;
+			if (getfrag(from, skb_put(skb, copy),
+					offset, copy, off, skb) < 0) {
+				__skb_trim(skb, off);
+				err = -EFAULT;
+				goto error;
+			}
+		} else if (flags & MSG_SPLICE_PAGES) {
+			struct msghdr *msg = from;
+
+			err = -EIO;
+			if (WARN_ON_ONCE(copy > msg->msg_iter.count))
+				goto error;
+
+			err = skb_splice_from_iter(skb, &msg->msg_iter, copy,
+						   sk->sk_allocation);
+			if (err < 0)
+				goto error;
+			copy = err;
+			wmem_alloc_delta += copy;
+		} else if (!zc) {
+			int i = skb_shinfo(skb)->nr_frags;
+
+			err = -ENOMEM;
+			if (!sk_page_frag_refill(sk, pfrag))
+				goto error;
+
+			skb_zcopy_downgrade_managed(skb);
+			if (!skb_can_coalesce(skb, i, pfrag->page,
+					      pfrag->offset)) {
+				err = -EMSGSIZE;
+				if (i == MAX_SKB_FRAGS)
+					goto error;
+
+				__skb_fill_page_desc(skb, i, pfrag->page,
+						     pfrag->offset, 0);
+				skb_shinfo(skb)->nr_frags = ++i;
+				get_page(pfrag->page);
+			}
+			copy = min_t(int, copy, pfrag->size - pfrag->offset);
+			if (getfrag(from,
+				    page_address(pfrag->page) + pfrag->offset,
+				    offset, copy, skb->len, skb) < 0)
+				goto error_efault;
+
+			pfrag->offset += copy;
+			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
+			skb_len_add(skb, copy);
+			wmem_alloc_delta += copy;
+		} else {
+			err = skb_zerocopy_iter_dgram(skb, from, copy);
+			if (err < 0)
+				goto error;
+		}
+		offset += copy;
+		length -= copy;
+	}
+
+	if (wmem_alloc_delta)
+		refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
+	return 0;
+
+error_efault:
+	err = -EFAULT;
+error:
+	net_zcopy_put_abort(uarg, extra_uref);
+	cork->length -= length;
+	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
+	refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
+	return err;
+}
+
+static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
+			 struct ipcm_cookie *ipc, struct rtable **rtp)
+{
+	struct ip_options_rcu *opt;
+	struct rtable *rt;
+
+	rt = *rtp;
+	if (unlikely(!rt))
+		return -EFAULT;
+
+	/*
+	 * setup for corking.
+	 */
+	opt = ipc->opt;
+	if (opt) {
+		if (!cork->opt) {
+			cork->opt = kmalloc(sizeof(struct ip_options) + 40,
+					    sk->sk_allocation);
+			if (unlikely(!cork->opt))
+				return -ENOBUFS;
+		}
+		memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
+		cork->flags |= IPCORK_OPT;
+		cork->addr = ipc->addr;
+	}
+
+	cork->fragsize = ip_sk_use_pmtu(sk) ?
+			 dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
+
+	if (!inetdev_valid_mtu(cork->fragsize))
+		return -ENETUNREACH;
+
+	cork->gso_size = ipc->gso_size;
+
+	cork->dst = &rt->dst;
+	/* We stole this route, caller should not release it. */
+	*rtp = NULL;
+
+	cork->length = 0;
+	cork->ttl = ipc->ttl;
+	cork->tos = ipc->tos;
+	cork->mark = ipc->sockc.mark;
+	cork->priority = ipc->priority;
+	cork->transmit_time = ipc->sockc.transmit_time;
+	cork->tx_flags = 0;
+	sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags);
+
+	return 0;
+}
+
+/*
+ *	ip_append_data() can make one large IP datagram from many pieces of
+ *	data.  Each piece will be held on the socket until
+ *	ip_push_pending_frames() is called. Each piece can be a page or
+ *	non-page data.
+ *
+ *	Not only UDP, other transport protocols - e.g. raw sockets - can use
+ *	this interface potentially.
+ *
+ *	LATER: length must be adjusted by pad at tail, when it is required.
+ */
+int ip_append_data(struct sock *sk, struct flowi4 *fl4,
+		   int getfrag(void *from, char *to, int offset, int len,
+			       int odd, struct sk_buff *skb),
+		   void *from, int length, int transhdrlen,
+		   struct ipcm_cookie *ipc, struct rtable **rtp,
+		   unsigned int flags)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	int err;
+
+	if (flags&MSG_PROBE)
+		return 0;
+
+	if (skb_queue_empty(&sk->sk_write_queue)) {
+		err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
+		if (err)
+			return err;
+	} else {
+		transhdrlen = 0;
+	}
+
+	return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
+				sk_page_frag(sk), getfrag,
+				from, length, transhdrlen, flags);
+}
+
+static void ip_cork_release(struct inet_cork *cork)
+{
+	cork->flags &= ~IPCORK_OPT;
+	kfree(cork->opt);
+	cork->opt = NULL;
+	dst_release(cork->dst);
+	cork->dst = NULL;
+}
+
+/*
+ *	Combined all pending IP fragments on the socket as one IP datagram
+ *	and push them out.
+ */
+struct sk_buff *__ip_make_skb(struct sock *sk,
+			      struct flowi4 *fl4,
+			      struct sk_buff_head *queue,
+			      struct inet_cork *cork)
+{
+	struct sk_buff *skb, *tmp_skb;
+	struct sk_buff **tail_skb;
+	struct inet_sock *inet = inet_sk(sk);
+	struct net *net = sock_net(sk);
+	struct ip_options *opt = NULL;
+	struct rtable *rt = (struct rtable *)cork->dst;
+	struct iphdr *iph;
+	__be16 df = 0;
+	__u8 ttl;
+
+	skb = __skb_dequeue(queue);
+	if (!skb)
+		goto out;
+	tail_skb = &(skb_shinfo(skb)->frag_list);
+
+	/* move skb->data to ip header from ext header */
+	if (skb->data < skb_network_header(skb))
+		__skb_pull(skb, skb_network_offset(skb));
+	while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
+		__skb_pull(tmp_skb, skb_network_header_len(skb));
+		*tail_skb = tmp_skb;
+		tail_skb = &(tmp_skb->next);
+		skb->len += tmp_skb->len;
+		skb->data_len += tmp_skb->len;
+		skb->truesize += tmp_skb->truesize;
+		tmp_skb->destructor = NULL;
+		tmp_skb->sk = NULL;
+	}
+
+	/* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
+	 * to fragment the frame generated here. No matter, what transforms
+	 * how transforms change size of the packet, it will come out.
+	 */
+	skb->ignore_df = ip_sk_ignore_df(sk);
+
+	/* DF bit is set when we want to see DF on outgoing frames.
+	 * If ignore_df is set too, we still allow to fragment this frame
+	 * locally. */
+	if (inet->pmtudisc == IP_PMTUDISC_DO ||
+	    inet->pmtudisc == IP_PMTUDISC_PROBE ||
+	    (skb->len <= dst_mtu(&rt->dst) &&
+	     ip_dont_fragment(sk, &rt->dst)))
+		df = htons(IP_DF);
+
+	if (cork->flags & IPCORK_OPT)
+		opt = cork->opt;
+
+	if (cork->ttl != 0)
+		ttl = cork->ttl;
+	else if (rt->rt_type == RTN_MULTICAST)
+		ttl = inet->mc_ttl;
+	else
+		ttl = ip_select_ttl(inet, &rt->dst);
+
+	iph = ip_hdr(skb);
+	iph->version = 4;
+	iph->ihl = 5;
+	iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
+	iph->frag_off = df;
+	iph->ttl = ttl;
+	iph->protocol = sk->sk_protocol;
+	ip_copy_addrs(iph, fl4);
+	ip_select_ident(net, skb, sk);
+
+	if (opt) {
+		iph->ihl += opt->optlen >> 2;
+		ip_options_build(skb, opt, cork->addr, rt);
+	}
+
+	skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
+	skb->mark = cork->mark;
+	skb->tstamp = cork->transmit_time;
+	/*
+	 * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
+	 * on dst refcount
+	 */
+	cork->dst = NULL;
+	skb_dst_set(skb, &rt->dst);
+
+	if (iph->protocol == IPPROTO_ICMP) {
+		u8 icmp_type;
+
+		/* For such sockets, transhdrlen is zero when do ip_append_data(),
+		 * so icmphdr does not in skb linear region and can not get icmp_type
+		 * by icmp_hdr(skb)->type.
+		 */
+		if (sk->sk_type == SOCK_RAW &&
+		    !inet_test_bit(HDRINCL, sk))
+			icmp_type = fl4->fl4_icmp_type;
+		else
+			icmp_type = icmp_hdr(skb)->type;
+		icmp_out_count(net, icmp_type);
+	}
+
+	ip_cork_release(cork);
+out:
+	return skb;
+}
+
+int ip_send_skb(struct net *net, struct sk_buff *skb)
+{
+	int err;
+
+	err = ip_local_out(net, skb->sk, skb);
+	if (err) {
+		if (err > 0)
+			err = net_xmit_errno(err);
+		if (err)
+			IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
+	}
+
+	return err;
+}
+
+int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
+{
+	struct sk_buff *skb;
+
+	skb = ip_finish_skb(sk, fl4);
+	if (!skb)
+		return 0;
+
+	/* Netfilter gets whole the not fragmented skb. */
+	return ip_send_skb(sock_net(sk), skb);
+}
+
+/*
+ *	Throw away all pending data on the socket.
+ */
+static void __ip_flush_pending_frames(struct sock *sk,
+				      struct sk_buff_head *queue,
+				      struct inet_cork *cork)
+{
+	struct sk_buff *skb;
+
+	while ((skb = __skb_dequeue_tail(queue)) != NULL)
+		kfree_skb(skb);
+
+	ip_cork_release(cork);
+}
+
+void ip_flush_pending_frames(struct sock *sk)
+{
+	__ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
+}
+
+struct sk_buff *ip_make_skb(struct sock *sk,
+			    struct flowi4 *fl4,
+			    int getfrag(void *from, char *to, int offset,
+					int len, int odd, struct sk_buff *skb),
+			    void *from, int length, int transhdrlen,
+			    struct ipcm_cookie *ipc, struct rtable **rtp,
+			    struct inet_cork *cork, unsigned int flags)
+{
+	struct sk_buff_head queue;
+	int err;
+
+	if (flags & MSG_PROBE)
+		return NULL;
+
+	__skb_queue_head_init(&queue);
+
+	cork->flags = 0;
+	cork->addr = 0;
+	cork->opt = NULL;
+	err = ip_setup_cork(sk, cork, ipc, rtp);
+	if (err)
+		return ERR_PTR(err);
+
+	err = __ip_append_data(sk, fl4, &queue, cork,
+			       &current->task_frag, getfrag,
+			       from, length, transhdrlen, flags);
+	if (err) {
+		__ip_flush_pending_frames(sk, &queue, cork);
+		return ERR_PTR(err);
+	}
+
+	return __ip_make_skb(sk, fl4, &queue, cork);
+}
+
+/*
+ *	Fetch data from kernel space and fill in checksum if needed.
+ */
+static int ip_reply_glue_bits(void *dptr, char *to, int offset,
+			      int len, int odd, struct sk_buff *skb)
+{
+	__wsum csum;
+
+	csum = csum_partial_copy_nocheck(dptr+offset, to, len);
+	skb->csum = csum_block_add(skb->csum, csum, odd);
+	return 0;
+}
+
+/*
+ *	Generic function to send a packet as reply to another packet.
+ *	Used to send some TCP resets/acks so far.
+ */
+void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
+			   const struct ip_options *sopt,
+			   __be32 daddr, __be32 saddr,
+			   const struct ip_reply_arg *arg,
+			   unsigned int len, u64 transmit_time, u32 txhash)
+{
+	struct ip_options_data replyopts;
+	struct ipcm_cookie ipc;
+	struct flowi4 fl4;
+	struct rtable *rt = skb_rtable(skb);
+	struct net *net = sock_net(sk);
+	struct sk_buff *nskb;
+	int err;
+	int oif;
+
+	if (__ip_options_echo(net, &replyopts.opt.opt, skb, sopt))
+		return;
+
+	ipcm_init(&ipc);
+	ipc.addr = daddr;
+	ipc.sockc.transmit_time = transmit_time;
+
+	if (replyopts.opt.opt.optlen) {
+		ipc.opt = &replyopts.opt;
+
+		if (replyopts.opt.opt.srr)
+			daddr = replyopts.opt.opt.faddr;
+	}
+
+	oif = arg->bound_dev_if;
+	if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
+		oif = skb->skb_iif;
+
+	flowi4_init_output(&fl4, oif,
+			   IP4_REPLY_MARK(net, skb->mark) ?: sk->sk_mark,
+			   RT_TOS(arg->tos),
+			   RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
+			   ip_reply_arg_flowi_flags(arg),
+			   daddr, saddr,
+			   tcp_hdr(skb)->source, tcp_hdr(skb)->dest,
+			   arg->uid);
+	security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
+	rt = ip_route_output_flow(net, &fl4, sk);
+	if (IS_ERR(rt))
+		return;
+
+	inet_sk(sk)->tos = arg->tos & ~INET_ECN_MASK;
+
+	sk->sk_protocol = ip_hdr(skb)->protocol;
+	sk->sk_bound_dev_if = arg->bound_dev_if;
+	sk->sk_sndbuf = READ_ONCE(sysctl_wmem_default);
+	ipc.sockc.mark = fl4.flowi4_mark;
+	err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
+			     len, 0, &ipc, &rt, MSG_DONTWAIT);
+	if (unlikely(err)) {
+		ip_flush_pending_frames(sk);
+		goto out;
+	}
+
+	nskb = skb_peek(&sk->sk_write_queue);
+	if (nskb) {
+		if (arg->csumoffset >= 0)
+			*((__sum16 *)skb_transport_header(nskb) +
+			  arg->csumoffset) = csum_fold(csum_add(nskb->csum,
+								arg->csum));
+		nskb->ip_summed = CHECKSUM_NONE;
+		nskb->mono_delivery_time = !!transmit_time;
+		if (txhash)
+			skb_set_hash(nskb, txhash, PKT_HASH_TYPE_L4);
+		ip_push_pending_frames(sk, &fl4);
+	}
+out:
+	ip_rt_put(rt);
+}
+
+void __init ip_init(void)
+{
+	ip_rt_init();
+	inet_initpeers();
+
+#if defined(CONFIG_IP_MULTICAST)
+	igmp_mc_init();
+#endif
+}