net/ipv6/output_core.c

   1 /*
   2  * IPv6 library code, needed by static components when full IPv6 support is
   3  * not configured or static.  These functions are needed by GSO/GRO implementation.
   4  */
   5 #include <linux/export.h>
   6 #include <net/ip.h>
   7 #include <net/ipv6.h>
   8 #include <net/ip6_fib.h>
   9 #include <net/addrconf.h>
  10 #include <net/secure_seq.h>
  11 #include <linux/netfilter.h>
  12
  13 static u32 __ipv6_select_ident(struct net *net,
  14                                const struct in6_addr *dst,
  15                                const struct in6_addr *src)
  16 {
  17         const struct {
  18                 struct in6_addr dst;
  19                 struct in6_addr src;
  20         } __aligned(SIPHASH_ALIGNMENT) combined = {
  21                 .dst = *dst,
  22                 .src = *src,
  23         };
  24         u32 hash, id;
  25
  26         /* Note the following code is not safe, but this is okay. */
  27         if (unlikely(siphash_key_is_zero(&net->ipv4.ip_id_key)))
  28                 get_random_bytes(&net->ipv4.ip_id_key,
  29                                  sizeof(net->ipv4.ip_id_key));
  30
  31         hash = siphash(&combined, sizeof(combined), &net->ipv4.ip_id_key);
  32
  33         /* Treat id of 0 as unset and if we get 0 back from ip_idents_reserve,
  34          * set the hight order instead thus minimizing possible future
  35          * collisions.
  36          */
  37         id = ip_idents_reserve(hash, 1);
  38         if (unlikely(!id))
  39                 id = 1 << 31;
  40
  41         return id;
  42 }
  43
  44 /* This function exists only for tap drivers that must support broken
  45  * clients requesting UFO without specifying an IPv6 fragment ID.
  46  *
  47  * This is similar to ipv6_select_ident() but we use an independent hash
  48  * seed to limit information leakage.
  49  *
  50  * The network header must be set before calling this.
  51  */
  52 __be32 ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb)
  53 {
  54         struct in6_addr buf[2];
  55         struct in6_addr *addrs;
  56         u32 id;
  57
  58         addrs = skb_header_pointer(skb,
  59                                    skb_network_offset(skb) +
  60                                    offsetof(struct ipv6hdr, saddr),
  61                                    sizeof(buf), buf);
  62         if (!addrs)
  63                 return 0;
  64
  65         id = __ipv6_select_ident(net, &addrs[1], &addrs[0]);
  66         return htonl(id);
  67 }
  68 EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident);
  69
  70 __be32 ipv6_select_ident(struct net *net,
  71                          const struct in6_addr *daddr,
  72                          const struct in6_addr *saddr)
  73 {
  74         u32 id;
  75
  76         id = __ipv6_select_ident(net, daddr, saddr);
  77         return htonl(id);
  78 }
  79 EXPORT_SYMBOL(ipv6_select_ident);
  80
  81 int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
  82 {
  83         unsigned int offset = sizeof(struct ipv6hdr);
  84         unsigned int packet_len = skb_tail_pointer(skb) -
  85                 skb_network_header(skb);
  86         int found_rhdr = 0;
  87         *nexthdr = &ipv6_hdr(skb)->nexthdr;
  88
  89         while (offset <= packet_len) {
  90                 struct ipv6_opt_hdr *exthdr;
  91
  92                 switch (**nexthdr) {
  93
  94                 case NEXTHDR_HOP:
  95                         break;
  96                 case NEXTHDR_ROUTING:
  97                         found_rhdr = 1;
  98                         break;
  99                 case NEXTHDR_DEST:
 100 #if IS_ENABLED(CONFIG_IPV6_MIP6)
 101                         if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0)
 102                                 break;
 103 #endif
 104                         if (found_rhdr)
 105                                 return offset;
 106                         break;
 107                 default:
 108                         return offset;
 109                 }
 110
 111                 if (offset + sizeof(struct ipv6_opt_hdr) > packet_len)
 112                         return -EINVAL;
 113
 114                 exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
 115                                                  offset);
 116                 offset += ipv6_optlen(exthdr);
 117                 if (offset > IPV6_MAXPLEN)
 118                         return -EINVAL;
 119                 *nexthdr = &exthdr->nexthdr;
 120         }
 121
 122         return -EINVAL;
 123 }
 124 EXPORT_SYMBOL(ip6_find_1stfragopt);
 125
 126 #if IS_ENABLED(CONFIG_IPV6)
 127 int ip6_dst_hoplimit(struct dst_entry *dst)
 128 {
 129         int hoplimit = dst_metric_raw(dst, RTAX_HOPLIMIT);
 130         if (hoplimit == 0) {
 131                 struct net_device *dev = dst->dev;
 132                 struct inet6_dev *idev;
 133
 134                 rcu_read_lock();
 135                 idev = __in6_dev_get(dev);
 136                 if (idev)
 137                         hoplimit = idev->cnf.hop_limit;
 138                 else
 139                         hoplimit = dev_net(dev)->ipv6.devconf_all->hop_limit;
 140                 rcu_read_unlock();
 141         }
 142         return hoplimit;
 143 }
 144 EXPORT_SYMBOL(ip6_dst_hoplimit);
 145 #endif
 146
 147 int __ip6_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
 148 {
 149         int len;
 150
 151         len = skb->len - sizeof(struct ipv6hdr);
 152         if (len > IPV6_MAXPLEN)
 153                 len = 0;
 154         ipv6_hdr(skb)->payload_len = htons(len);
 155         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
 156
 157         /* if egress device is enslaved to an L3 master device pass the
 158          * skb to its handler for processing
 159          */
 160         skb = l3mdev_ip6_out(sk, skb);
 161         if (unlikely(!skb))
 162                 return 0;
 163
 164         skb->protocol = htons(ETH_P_IPV6);
 165
 166         return nf_hook(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
 167                        net, sk, skb, NULL, skb_dst(skb)->dev,
 168                        dst_output);
 169 }
 170 EXPORT_SYMBOL_GPL(__ip6_local_out);
 171
 172 int ip6_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
 173 {
 174         int err;
 175
 176         err = __ip6_local_out(net, sk, skb);
 177         if (likely(err == 1))
 178                 err = dst_output(net, sk, skb);
 179
 180         return err;
 181 }
 182 EXPORT_SYMBOL_GPL(ip6_local_out);