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 <net/protocol.h>
 14#include <net/ipv6.h>
 15#include <net/udp.h>
 16#include <net/ip6_checksum.h>
 17#include "ip6_offload.h"
 18
 19static int udp6_ufo_send_check(struct sk_buff *skb)
 20{
 21	const struct ipv6hdr *ipv6h;
 22	struct udphdr *uh;
 23
 24	if (!pskb_may_pull(skb, sizeof(*uh)))
 25		return -EINVAL;
 26
 27	if (likely(!skb->encapsulation)) {
 28		ipv6h = ipv6_hdr(skb);
 29		uh = udp_hdr(skb);
 30
 31		uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
 32					     IPPROTO_UDP, 0);
 33		skb->csum_start = skb_transport_header(skb) - skb->head;
 34		skb->csum_offset = offsetof(struct udphdr, check);
 35		skb->ip_summed = CHECKSUM_PARTIAL;
 36	}
 37
 38	return 0;
 39}
 40
 41static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 42					 netdev_features_t features)
 43{
 44	struct sk_buff *segs = ERR_PTR(-EINVAL);
 45	unsigned int mss;
 46	unsigned int unfrag_ip6hlen, unfrag_len;
 47	struct frag_hdr *fptr;
 48	u8 *packet_start, *prevhdr;
 49	u8 nexthdr;
 50	u8 frag_hdr_sz = sizeof(struct frag_hdr);
 51	int offset;
 52	__wsum csum;
 53	int tnl_hlen;
 54
 55	mss = skb_shinfo(skb)->gso_size;
 56	if (unlikely(skb->len <= mss))
 57		goto out;
 58
 59	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
 60		/* Packet is from an untrusted source, reset gso_segs. */
 61		int type = skb_shinfo(skb)->gso_type;
 62
 63		if (unlikely(type & ~(SKB_GSO_UDP |
 64				      SKB_GSO_DODGY |
 65				      SKB_GSO_UDP_TUNNEL |
 66				      SKB_GSO_GRE |
 67				      SKB_GSO_IPIP |
 68				      SKB_GSO_SIT |
 69				      SKB_GSO_MPLS) ||
 70			     !(type & (SKB_GSO_UDP))))
 71			goto out;
 72
 73		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 74
 75		segs = NULL;
 76		goto out;
 77	}
 78
 79	if (skb->encapsulation && skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL)
 80		segs = skb_udp_tunnel_segment(skb, features);
 81	else {
 82		/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
 83		 * do checksum of UDP packets sent as multiple IP fragments.
 84		 */
 85		offset = skb_checksum_start_offset(skb);
 86		csum = skb_checksum(skb, offset, skb->len - offset, 0);
 87		offset += skb->csum_offset;
 88		*(__sum16 *)(skb->data + offset) = csum_fold(csum);
 89		skb->ip_summed = CHECKSUM_NONE;
 90
 91		/* Check if there is enough headroom to insert fragment header. */
 92		tnl_hlen = skb_tnl_header_len(skb);
 93		if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
 94			if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
 95				goto out;
 96		}
 97
 98		/* Find the unfragmentable header and shift it left by frag_hdr_sz
 99		 * bytes to insert fragment header.
100		 */
101		unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
102		nexthdr = *prevhdr;
103		*prevhdr = NEXTHDR_FRAGMENT;
104		unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
105			     unfrag_ip6hlen + tnl_hlen;
106		packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
107		memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
108
109		SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
110		skb->mac_header -= frag_hdr_sz;
111		skb->network_header -= frag_hdr_sz;
112
113		fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
114		fptr->nexthdr = nexthdr;
115		fptr->reserved = 0;
116		fptr->identification = skb_shinfo(skb)->ip6_frag_id;
117
118		/* Fragment the skb. ipv6 header and the remaining fields of the
119		 * fragment header are updated in ipv6_gso_segment()
120		 */
121		segs = skb_segment(skb, features);
122	}
123
124out:
125	return segs;
126}
127static const struct net_offload udpv6_offload = {
128	.callbacks = {
129		.gso_send_check =	udp6_ufo_send_check,
130		.gso_segment	=	udp6_ufo_fragment,
131	},
132};
133
134int __init udp_offload_init(void)
135{
136	return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
137}