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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 <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 
 20 static 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_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
 39                 /* Packet is from an untrusted source, reset gso_segs. */
 40 
 41                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 42 
 43                 /* Set the IPv6 fragment id if not set yet */
 44                 if (!skb_shinfo(skb)->ip6_frag_id)
 45                         ipv6_proxy_select_ident(dev_net(skb->dev), skb);
 46 
 47                 segs = NULL;
 48                 goto out;
 49         }
 50 
 51         if (skb->encapsulation && skb_shinfo(skb)->gso_type &
 52             (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))
 53                 segs = skb_udp_tunnel_segment(skb, features, true);
 54         else {
 55                 const struct ipv6hdr *ipv6h;
 56                 struct udphdr *uh;
 57 
 58                 if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 59                         goto out;
 60 
 61                 /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
 62                  * do checksum of UDP packets sent as multiple IP fragments.
 63                  */
 64 
 65                 uh = udp_hdr(skb);
 66                 ipv6h = ipv6_hdr(skb);
 67 
 68                 uh->check = 0;
 69                 csum = skb_checksum(skb, 0, skb->len, 0);
 70                 uh->check = udp_v6_check(skb->len, &ipv6h->saddr,
 71                                           &ipv6h->daddr, csum);
 72                 if (uh->check == 0)
 73                         uh->check = CSUM_MANGLED_0;
 74 
 75                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 76 
 77                 /* If there is no outer header we can fake a checksum offload
 78                  * due to the fact that we have already done the checksum in
 79                  * software prior to segmenting the frame.
 80                  */
 81                 if (!skb->encap_hdr_csum)
 82                         features |= NETIF_F_HW_CSUM;
 83 
 84                 /* Check if there is enough headroom to insert fragment header. */
 85                 tnl_hlen = skb_tnl_header_len(skb);
 86                 if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
 87                         if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
 88                                 goto out;
 89                 }
 90 
 91                 /* Find the unfragmentable header and shift it left by frag_hdr_sz
 92                  * bytes to insert fragment header.
 93                  */
 94                 err = ip6_find_1stfragopt(skb, &prevhdr);
 95                 if (err < 0)
 96                         return ERR_PTR(err);
 97                 unfrag_ip6hlen = err;
 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                 if (!skb_shinfo(skb)->ip6_frag_id)
113                         ipv6_proxy_select_ident(dev_net(skb->dev), skb);
114                 fptr->identification = skb_shinfo(skb)->ip6_frag_id;
115 
116                 /* Fragment the skb. ipv6 header and the remaining fields of the
117                  * fragment header are updated in ipv6_gso_segment()
118                  */
119                 segs = skb_segment(skb, features);
120         }
121 
122 out:
123         return segs;
124 }
125 
126 static struct sk_buff **udp6_gro_receive(struct sk_buff **head,
127                                          struct sk_buff *skb)
128 {
129         struct udphdr *uh = udp_gro_udphdr(skb);
130 
131         if (unlikely(!uh))
132                 goto flush;
133 
134         /* Don't bother verifying checksum if we're going to flush anyway. */
135         if (NAPI_GRO_CB(skb)->flush)
136                 goto skip;
137 
138         if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
139                                                  ip6_gro_compute_pseudo))
140                 goto flush;
141         else if (uh->check)
142                 skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
143                                              ip6_gro_compute_pseudo);
144 
145 skip:
146         NAPI_GRO_CB(skb)->is_ipv6 = 1;
147         return udp_gro_receive(head, skb, uh, udp6_lib_lookup_skb);
148 
149 flush:
150         NAPI_GRO_CB(skb)->flush = 1;
151         return NULL;
152 }
153 
154 static int udp6_gro_complete(struct sk_buff *skb, int nhoff)
155 {
156         const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
157         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
158 
159         if (uh->check) {
160                 skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
161                 uh->check = ~udp_v6_check(skb->len - nhoff, &ipv6h->saddr,
162                                           &ipv6h->daddr, 0);
163         } else {
164                 skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
165         }
166 
167         return udp_gro_complete(skb, nhoff, udp6_lib_lookup_skb);
168 }
169 
170 static const struct net_offload udpv6_offload = {
171         .callbacks = {
172                 .gso_segment    =       udp6_ufo_fragment,
173                 .gro_receive    =       udp6_gro_receive,
174                 .gro_complete   =       udp6_gro_complete,
175         },
176 };
177 
178 int udpv6_offload_init(void)
179 {
180         return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
181 }
182 
183 int udpv6_offload_exit(void)
184 {
185         return inet6_del_offload(&udpv6_offload, IPPROTO_UDP);
186 }
187 

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