1/*
  2 *	IPV6 GSO/GRO offload support
  3 *	Linux INET6 implementation
  4 *
  5 *	This program is free software; you can redistribute it and/or
  6 *      modify it under the terms of the GNU General Public License
  7 *      as published by the Free Software Foundation; either version
  8 *      2 of the License, or (at your option) any later version.
  9 *
 10 *      UDPv6 GSO support
 11 */
 12#include <linux/skbuff.h>
 13#include <linux/netdevice.h>
 14#include <net/protocol.h>
 15#include <net/ipv6.h>
 16#include <net/udp.h>
 17#include <net/ip6_checksum.h>
 18#include "ip6_offload.h"
 19
 20static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 21					 netdev_features_t features)
 22{
 23	struct sk_buff *segs = ERR_PTR(-EINVAL);
 24	unsigned int mss;
 25	unsigned int unfrag_ip6hlen, unfrag_len;
 26	struct frag_hdr *fptr;
 27	u8 *packet_start, *prevhdr;
 28	u8 nexthdr;
 29	u8 frag_hdr_sz = sizeof(struct frag_hdr);
 30	__wsum csum;
 31	int tnl_hlen;
 32	int err;
 33
 34	mss = skb_shinfo(skb)->gso_size;
 35	if (unlikely(skb->len <= mss))
 36		goto out;
 37
 38	if (skb->encapsulation && skb_shinfo(skb)->gso_type &
 39	    (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))
 40		segs = skb_udp_tunnel_segment(skb, features, true);
 41	else {
 42		const struct ipv6hdr *ipv6h;
 43		struct udphdr *uh;
 44
 45		if (!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP))
 46			goto out;
 47
 48		if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 49			goto out;
 50
 51		/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
 52		 * do checksum of UDP packets sent as multiple IP fragments.
 53		 */
 54
 55		uh = udp_hdr(skb);
 56		ipv6h = ipv6_hdr(skb);
 57
 58		uh->check = 0;
 59		csum = skb_checksum(skb, 0, skb->len, 0);
 60		uh->check = udp_v6_check(skb->len, &ipv6h->saddr,
 61					  &ipv6h->daddr, csum);
 62		if (uh->check == 0)
 63			uh->check = CSUM_MANGLED_0;
 64
 65		skb->ip_summed = CHECKSUM_UNNECESSARY;
 66
 67		/* If there is no outer header we can fake a checksum offload
 68		 * due to the fact that we have already done the checksum in
 69		 * software prior to segmenting the frame.
 70		 */
 71		if (!skb->encap_hdr_csum)
 72			features |= NETIF_F_HW_CSUM;
 73
 74		/* Check if there is enough headroom to insert fragment header. */
 75		tnl_hlen = skb_tnl_header_len(skb);
 76		if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
 77			if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
 78				goto out;
 79		}
 80
 81		/* Find the unfragmentable header and shift it left by frag_hdr_sz
 82		 * bytes to insert fragment header.
 83		 */
 84		err = ip6_find_1stfragopt(skb, &prevhdr);
 85		if (err < 0)
 86			return ERR_PTR(err);
 87		unfrag_ip6hlen = err;
 88		nexthdr = *prevhdr;
 89		*prevhdr = NEXTHDR_FRAGMENT;
 90		unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
 91			     unfrag_ip6hlen + tnl_hlen;
 92		packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
 93		memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
 94
 95		SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
 96		skb->mac_header -= frag_hdr_sz;
 97		skb->network_header -= frag_hdr_sz;
 98
 99		fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
100		fptr->nexthdr = nexthdr;
101		fptr->reserved = 0;
102		fptr->identification = ipv6_proxy_select_ident(dev_net(skb->dev), skb);
103
104		/* Fragment the skb. ipv6 header and the remaining fields of the
105		 * fragment header are updated in ipv6_gso_segment()
106		 */
107		segs = skb_segment(skb, features);
108	}
109
110out:
111	return segs;
112}
113
114static struct sk_buff **udp6_gro_receive(struct sk_buff **head,
115					 struct sk_buff *skb)
116{
117	struct udphdr *uh = udp_gro_udphdr(skb);
118
119	if (unlikely(!uh))
120		goto flush;
121
122	/* Don't bother verifying checksum if we're going to flush anyway. */
123	if (NAPI_GRO_CB(skb)->flush)
124		goto skip;
125
126	if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
127						 ip6_gro_compute_pseudo))
128		goto flush;
129	else if (uh->check)
130		skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
131					     ip6_gro_compute_pseudo);
132
133skip:
134	NAPI_GRO_CB(skb)->is_ipv6 = 1;
135	return udp_gro_receive(head, skb, uh, udp6_lib_lookup_skb);
136
137flush:
138	NAPI_GRO_CB(skb)->flush = 1;
139	return NULL;
140}
141
142static int udp6_gro_complete(struct sk_buff *skb, int nhoff)
143{
144	const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
145	struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
146
147	if (uh->check) {
148		skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
149		uh->check = ~udp_v6_check(skb->len - nhoff, &ipv6h->saddr,
150					  &ipv6h->daddr, 0);
151	} else {
152		skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
153	}
154
155	return udp_gro_complete(skb, nhoff, udp6_lib_lookup_skb);
156}
157
158static const struct net_offload udpv6_offload = {
159	.callbacks = {
160		.gso_segment	=	udp6_ufo_fragment,
161		.gro_receive	=	udp6_gro_receive,
162		.gro_complete	=	udp6_gro_complete,
163	},
164};
165
166int udpv6_offload_init(void)
167{
168	return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
169}
170
171int udpv6_offload_exit(void)
172{
173	return inet6_del_offload(&udpv6_offload, IPPROTO_UDP);
174}