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Linux/net/ipv6/udp_offload.c

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  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 
 19 static int udp6_ufo_send_check(struct sk_buff *skb)
 20 {
 21         const struct ipv6hdr *ipv6h;
 22         struct udphdr *uh;
 23 
 24         /* UDP Tunnel offload on ipv6 is not yet supported. */
 25         if (skb->encapsulation)
 26                 return -EINVAL;
 27 
 28         if (!pskb_may_pull(skb, sizeof(*uh)))
 29                 return -EINVAL;
 30 
 31         ipv6h = ipv6_hdr(skb);
 32         uh = udp_hdr(skb);
 33 
 34         uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
 35                                      IPPROTO_UDP, 0);
 36         skb->csum_start = skb_transport_header(skb) - skb->head;
 37         skb->csum_offset = offsetof(struct udphdr, check);
 38         skb->ip_summed = CHECKSUM_PARTIAL;
 39         return 0;
 40 }
 41 
 42 static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 43         netdev_features_t features)
 44 {
 45         struct sk_buff *segs = ERR_PTR(-EINVAL);
 46         unsigned int mss;
 47         unsigned int unfrag_ip6hlen, unfrag_len;
 48         struct frag_hdr *fptr;
 49         u8 *packet_start, *prevhdr;
 50         u8 nexthdr;
 51         u8 frag_hdr_sz = sizeof(struct frag_hdr);
 52         int offset;
 53         __wsum csum;
 54         int tnl_hlen;
 55 
 56         mss = skb_shinfo(skb)->gso_size;
 57         if (unlikely(skb->len <= mss))
 58                 goto out;
 59 
 60         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
 61                 /* Packet is from an untrusted source, reset gso_segs. */
 62                 int type = skb_shinfo(skb)->gso_type;
 63 
 64                 if (unlikely(type & ~(SKB_GSO_UDP |
 65                                       SKB_GSO_DODGY |
 66                                       SKB_GSO_UDP_TUNNEL |
 67                                       SKB_GSO_GRE |
 68                                       SKB_GSO_MPLS) ||
 69                              !(type & (SKB_GSO_UDP))))
 70                         goto out;
 71 
 72                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 73 
 74                 segs = NULL;
 75                 goto out;
 76         }
 77 
 78         /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
 79          * do checksum of UDP packets sent as multiple IP fragments.
 80          */
 81         offset = skb_checksum_start_offset(skb);
 82         csum = skb_checksum(skb, offset, skb->len - offset, 0);
 83         offset += skb->csum_offset;
 84         *(__sum16 *)(skb->data + offset) = csum_fold(csum);
 85         skb->ip_summed = CHECKSUM_NONE;
 86 
 87         /* Check if there is enough headroom to insert fragment header. */
 88         tnl_hlen = skb_tnl_header_len(skb);
 89         if (skb_headroom(skb) < (tnl_hlen + frag_hdr_sz)) {
 90                 if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
 91                         goto out;
 92         }
 93 
 94         /* Find the unfragmentable header and shift it left by frag_hdr_sz
 95          * bytes to insert fragment header.
 96          */
 97         unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
 98         nexthdr = *prevhdr;
 99         *prevhdr = NEXTHDR_FRAGMENT;
100         unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
101                      unfrag_ip6hlen + tnl_hlen;
102         packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
103         memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
104 
105         SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
106         skb->mac_header -= frag_hdr_sz;
107         skb->network_header -= frag_hdr_sz;
108 
109         fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
110         fptr->nexthdr = nexthdr;
111         fptr->reserved = 0;
112         ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
113 
114         /* Fragment the skb. ipv6 header and the remaining fields of the
115          * fragment header are updated in ipv6_gso_segment()
116          */
117         segs = skb_segment(skb, features);
118 
119 out:
120         return segs;
121 }
122 static const struct net_offload udpv6_offload = {
123         .callbacks = {
124                 .gso_send_check =       udp6_ufo_send_check,
125                 .gso_segment    =       udp6_ufo_fragment,
126         },
127 };
128 
129 int __init udp_offload_init(void)
130 {
131         return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
132 }
133 

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