net/sched/sch_frag.c

   1 // SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
   2 #include <net/netlink.h>
   3 #include <net/sch_generic.h>
   4 #include <net/dst.h>
   5 #include <net/ip.h>
   6 #include <net/ip6_fib.h>
   7
   8 struct sch_frag_data {
   9         unsigned long dst;
  10         struct qdisc_skb_cb cb;
  11         __be16 inner_protocol;
  12         u16 vlan_tci;
  13         __be16 vlan_proto;
  14         unsigned int l2_len;
  15         u8 l2_data[VLAN_ETH_HLEN];
  16         int (*xmit)(struct sk_buff *skb);
  17 };
  18
  19 static DEFINE_PER_CPU(struct sch_frag_data, sch_frag_data_storage);
  20
  21 static int sch_frag_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
  22 {
  23         struct sch_frag_data *data = this_cpu_ptr(&sch_frag_data_storage);
  24
  25         if (skb_cow_head(skb, data->l2_len) < 0) {
  26                 kfree_skb(skb);
  27                 return -ENOMEM;
  28         }
  29
  30         __skb_dst_copy(skb, data->dst);
  31         *qdisc_skb_cb(skb) = data->cb;
  32         skb->inner_protocol = data->inner_protocol;
  33         if (data->vlan_tci & VLAN_CFI_MASK)
  34                 __vlan_hwaccel_put_tag(skb, data->vlan_proto,
  35                                        data->vlan_tci & ~VLAN_CFI_MASK);
  36         else
  37                 __vlan_hwaccel_clear_tag(skb);
  38
  39         /* Reconstruct the MAC header.  */
  40         skb_push(skb, data->l2_len);
  41         memcpy(skb->data, &data->l2_data, data->l2_len);
  42         skb_postpush_rcsum(skb, skb->data, data->l2_len);
  43         skb_reset_mac_header(skb);
  44
  45         return data->xmit(skb);
  46 }
  47
  48 static void sch_frag_prepare_frag(struct sk_buff *skb,
  49                                   int (*xmit)(struct sk_buff *skb))
  50 {
  51         unsigned int hlen = skb_network_offset(skb);
  52         struct sch_frag_data *data;
  53
  54         data = this_cpu_ptr(&sch_frag_data_storage);
  55         data->dst = skb->_skb_refdst;
  56         data->cb = *qdisc_skb_cb(skb);
  57         data->xmit = xmit;
  58         data->inner_protocol = skb->inner_protocol;
  59         if (skb_vlan_tag_present(skb))
  60                 data->vlan_tci = skb_vlan_tag_get(skb) | VLAN_CFI_MASK;
  61         else
  62                 data->vlan_tci = 0;
  63         data->vlan_proto = skb->vlan_proto;
  64         data->l2_len = hlen;
  65         memcpy(&data->l2_data, skb->data, hlen);
  66
  67         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
  68         skb_pull(skb, hlen);
  69 }
  70
  71 static unsigned int
  72 sch_frag_dst_get_mtu(const struct dst_entry *dst)
  73 {
  74         return dst->dev->mtu;
  75 }
  76
  77 static struct dst_ops sch_frag_dst_ops = {
  78         .family = AF_UNSPEC,
  79         .mtu = sch_frag_dst_get_mtu,
  80 };
  81
  82 static int sch_fragment(struct net *net, struct sk_buff *skb,
  83                         u16 mru, int (*xmit)(struct sk_buff *skb))
  84 {
  85         int ret = -1;
  86
  87         if (skb_network_offset(skb) > VLAN_ETH_HLEN) {
  88                 net_warn_ratelimited("L2 header too long to fragment\n");
  89                 goto err;
  90         }
  91
  92         if (skb_protocol(skb, true) == htons(ETH_P_IP)) {
  93                 struct rtable sch_frag_rt = { 0 };
  94                 unsigned long orig_dst;
  95
  96                 sch_frag_prepare_frag(skb, xmit);
  97                 dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL, 1,
  98                          DST_OBSOLETE_NONE, DST_NOCOUNT);
  99                 sch_frag_rt.dst.dev = skb->dev;
 100
 101                 orig_dst = skb->_skb_refdst;
 102                 skb_dst_set_noref(skb, &sch_frag_rt.dst);
 103                 IPCB(skb)->frag_max_size = mru;
 104
 105                 ret = ip_do_fragment(net, skb->sk, skb, sch_frag_xmit);
 106                 refdst_drop(orig_dst);
 107         } else if (skb_protocol(skb, true) == htons(ETH_P_IPV6)) {
 108                 unsigned long orig_dst;
 109                 struct rt6_info sch_frag_rt;
 110
 111                 sch_frag_prepare_frag(skb, xmit);
 112                 memset(&sch_frag_rt, 0, sizeof(sch_frag_rt));
 113                 dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL, 1,
 114                          DST_OBSOLETE_NONE, DST_NOCOUNT);
 115                 sch_frag_rt.dst.dev = skb->dev;
 116
 117                 orig_dst = skb->_skb_refdst;
 118                 skb_dst_set_noref(skb, &sch_frag_rt.dst);
 119                 IP6CB(skb)->frag_max_size = mru;
 120
 121                 ret = ipv6_stub->ipv6_fragment(net, skb->sk, skb,
 122                                                sch_frag_xmit);
 123                 refdst_drop(orig_dst);
 124         } else {
 125                 net_warn_ratelimited("Fail frag %s: eth=%x, MRU=%d, MTU=%d\n",
 126                                      netdev_name(skb->dev),
 127                                      ntohs(skb_protocol(skb, true)), mru,
 128                                      skb->dev->mtu);
 129                 goto err;
 130         }
 131
 132         return ret;
 133 err:
 134         kfree_skb(skb);
 135         return ret;
 136 }
 137
 138 int sch_frag_xmit_hook(struct sk_buff *skb, int (*xmit)(struct sk_buff *skb))
 139 {
 140         u16 mru = qdisc_skb_cb(skb)->mru;
 141         int err;
 142
 143         if (mru && skb->len > mru + skb->dev->hard_header_len)
 144                 err = sch_fragment(dev_net(skb->dev), skb, mru, xmit);
 145         else
 146                 err = xmit(skb);
 147
 148         return err;
 149 }
 150 EXPORT_SYMBOL_GPL(sch_frag_xmit_hook);