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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 
 33         mss = skb_shinfo(skb)->gso_size;
 34         if (unlikely(skb->len <= mss))
 35                 goto out;
 36 
 37         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
 38                 /* Packet is from an untrusted source, reset gso_segs. */
 39 
 40                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 41 
 42                 /* Set the IPv6 fragment id if not set yet */
 43                 if (!skb_shinfo(skb)->ip6_frag_id)
 44                         ipv6_proxy_select_ident(dev_net(skb->dev), skb);
 45 
 46                 segs = NULL;
 47                 goto out;
 48         }
 49 
 50         if (skb->encapsulation && skb_shinfo(skb)->gso_type &
 51             (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))
 52                 segs = skb_udp_tunnel_segment(skb, features, true);
 53         else {
 54                 const struct ipv6hdr *ipv6h;
 55                 struct udphdr *uh;
 56 
 57                 if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 58                         goto out;
 59 
 60                 /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
 61                  * do checksum of UDP packets sent as multiple IP fragments.
 62                  */
 63 
 64                 uh = udp_hdr(skb);
 65                 ipv6h = ipv6_hdr(skb);
 66 
 67                 uh->check = 0;
 68                 csum = skb_checksum(skb, 0, skb->len, 0);
 69                 uh->check = udp_v6_check(skb->len, &ipv6h->saddr,
 70                                           &ipv6h->daddr, csum);
 71                 if (uh->check == 0)
 72                         uh->check = CSUM_MANGLED_0;
 73 
 74                 skb->ip_summed = CHECKSUM_NONE;
 75 
 76                 /* If there is no outer header we can fake a checksum offload
 77                  * due to the fact that we have already done the checksum in
 78                  * software prior to segmenting the frame.
 79                  */
 80                 if (!skb->encap_hdr_csum)
 81                         features |= NETIF_F_HW_CSUM;
 82 
 83                 /* Check if there is enough headroom to insert fragment header. */
 84                 tnl_hlen = skb_tnl_header_len(skb);
 85                 if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
 86                         if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
 87                                 goto out;
 88                 }
 89 
 90                 /* Find the unfragmentable header and shift it left by frag_hdr_sz
 91                  * bytes to insert fragment header.
 92                  */
 93                 unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
 94                 nexthdr = *prevhdr;
 95                 *prevhdr = NEXTHDR_FRAGMENT;
 96                 unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
 97                              unfrag_ip6hlen + tnl_hlen;
 98                 packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
 99                 memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
100 
101                 SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
102                 skb->mac_header -= frag_hdr_sz;
103                 skb->network_header -= frag_hdr_sz;
104 
105                 fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
106                 fptr->nexthdr = nexthdr;
107                 fptr->reserved = 0;
108                 if (!skb_shinfo(skb)->ip6_frag_id)
109                         ipv6_proxy_select_ident(dev_net(skb->dev), skb);
110                 fptr->identification = skb_shinfo(skb)->ip6_frag_id;
111 
112                 /* Fragment the skb. ipv6 header and the remaining fields of the
113                  * fragment header are updated in ipv6_gso_segment()
114                  */
115                 segs = skb_segment(skb, features);
116         }
117 
118 out:
119         return segs;
120 }
121 
122 static struct sk_buff **udp6_gro_receive(struct sk_buff **head,
123                                          struct sk_buff *skb)
124 {
125         struct udphdr *uh = udp_gro_udphdr(skb);
126 
127         if (unlikely(!uh))
128                 goto flush;
129 
130         /* Don't bother verifying checksum if we're going to flush anyway. */
131         if (NAPI_GRO_CB(skb)->flush)
132                 goto skip;
133 
134         if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
135                                                  ip6_gro_compute_pseudo))
136                 goto flush;
137         else if (uh->check)
138                 skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
139                                              ip6_gro_compute_pseudo);
140 
141 skip:
142         NAPI_GRO_CB(skb)->is_ipv6 = 1;
143         return udp_gro_receive(head, skb, uh, udp6_lib_lookup_skb);
144 
145 flush:
146         NAPI_GRO_CB(skb)->flush = 1;
147         return NULL;
148 }
149 
150 static int udp6_gro_complete(struct sk_buff *skb, int nhoff)
151 {
152         const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
153         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
154 
155         if (uh->check) {
156                 skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
157                 uh->check = ~udp_v6_check(skb->len - nhoff, &ipv6h->saddr,
158                                           &ipv6h->daddr, 0);
159         } else {
160                 skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
161         }
162 
163         return udp_gro_complete(skb, nhoff, udp6_lib_lookup_skb);
164 }
165 
166 static const struct net_offload udpv6_offload = {
167         .callbacks = {
168                 .gso_segment    =       udp6_ufo_fragment,
169                 .gro_receive    =       udp6_gro_receive,
170                 .gro_complete   =       udp6_gro_complete,
171         },
172 };
173 
174 int udpv6_offload_init(void)
175 {
176         return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
177 }
178 
179 int udpv6_offload_exit(void)
180 {
181         return inet6_del_offload(&udpv6_offload, IPPROTO_UDP);
182 }
183 

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