net/sched/sch_frag.c

0001 // SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
0002 #include <linux/if_vlan.h>
0003 #include <net/netlink.h>
0004 #include <net/sch_generic.h>
0005 #include <net/pkt_sched.h>
0006 #include <net/dst.h>
0007 #include <net/ip.h>
0008 #include <net/ip6_fib.h>
0009
0010 struct sch_frag_data {
0011     unsigned long dst;
0012     struct qdisc_skb_cb cb;
0013     __be16 inner_protocol;
0014     u16 vlan_tci;
0015     __be16 vlan_proto;
0016     unsigned int l2_len;
0017     u8 l2_data[VLAN_ETH_HLEN];
0018     int (*xmit)(struct sk_buff *skb);
0019 };
0020
0021 static DEFINE_PER_CPU(struct sch_frag_data, sch_frag_data_storage);
0022
0023 static int sch_frag_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
0024 {
0025     struct sch_frag_data *data = this_cpu_ptr(&sch_frag_data_storage);
0026
0027     if (skb_cow_head(skb, data->l2_len) < 0) {
0028         kfree_skb(skb);
0029         return -ENOMEM;
0030     }
0031
0032     __skb_dst_copy(skb, data->dst);
0033     *qdisc_skb_cb(skb) = data->cb;
0034     skb->inner_protocol = data->inner_protocol;
0035     if (data->vlan_tci & VLAN_CFI_MASK)
0036         __vlan_hwaccel_put_tag(skb, data->vlan_proto,
0037                        data->vlan_tci & ~VLAN_CFI_MASK);
0038     else
0039         __vlan_hwaccel_clear_tag(skb);
0040
0041     /* Reconstruct the MAC header.  */
0042     skb_push(skb, data->l2_len);
0043     memcpy(skb->data, &data->l2_data, data->l2_len);
0044     skb_postpush_rcsum(skb, skb->data, data->l2_len);
0045     skb_reset_mac_header(skb);
0046
0047     return data->xmit(skb);
0048 }
0049
0050 static void sch_frag_prepare_frag(struct sk_buff *skb,
0051                   int (*xmit)(struct sk_buff *skb))
0052 {
0053     unsigned int hlen = skb_network_offset(skb);
0054     struct sch_frag_data *data;
0055
0056     data = this_cpu_ptr(&sch_frag_data_storage);
0057     data->dst = skb->_skb_refdst;
0058     data->cb = *qdisc_skb_cb(skb);
0059     data->xmit = xmit;
0060     data->inner_protocol = skb->inner_protocol;
0061     if (skb_vlan_tag_present(skb))
0062         data->vlan_tci = skb_vlan_tag_get(skb) | VLAN_CFI_MASK;
0063     else
0064         data->vlan_tci = 0;
0065     data->vlan_proto = skb->vlan_proto;
0066     data->l2_len = hlen;
0067     memcpy(&data->l2_data, skb->data, hlen);
0068
0069     memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
0070     skb_pull(skb, hlen);
0071 }
0072
0073 static unsigned int
0074 sch_frag_dst_get_mtu(const struct dst_entry *dst)
0075 {
0076     return dst->dev->mtu;
0077 }
0078
0079 static struct dst_ops sch_frag_dst_ops = {
0080     .family = AF_UNSPEC,
0081     .mtu = sch_frag_dst_get_mtu,
0082 };
0083
0084 static int sch_fragment(struct net *net, struct sk_buff *skb,
0085             u16 mru, int (*xmit)(struct sk_buff *skb))
0086 {
0087     int ret = -1;
0088
0089     if (skb_network_offset(skb) > VLAN_ETH_HLEN) {
0090         net_warn_ratelimited("L2 header too long to fragment\n");
0091         goto err;
0092     }
0093
0094     if (skb_protocol(skb, true) == htons(ETH_P_IP)) {
0095         struct rtable sch_frag_rt = { 0 };
0096         unsigned long orig_dst;
0097
0098         sch_frag_prepare_frag(skb, xmit);
0099         dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL, 1,
0100              DST_OBSOLETE_NONE, DST_NOCOUNT);
0101         sch_frag_rt.dst.dev = skb->dev;
0102
0103         orig_dst = skb->_skb_refdst;
0104         skb_dst_set_noref(skb, &sch_frag_rt.dst);
0105         IPCB(skb)->frag_max_size = mru;
0106
0107         ret = ip_do_fragment(net, skb->sk, skb, sch_frag_xmit);
0108         refdst_drop(orig_dst);
0109     } else if (skb_protocol(skb, true) == htons(ETH_P_IPV6)) {
0110         unsigned long orig_dst;
0111         struct rt6_info sch_frag_rt;
0112
0113         sch_frag_prepare_frag(skb, xmit);
0114         memset(&sch_frag_rt, 0, sizeof(sch_frag_rt));
0115         dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL, 1,
0116              DST_OBSOLETE_NONE, DST_NOCOUNT);
0117         sch_frag_rt.dst.dev = skb->dev;
0118
0119         orig_dst = skb->_skb_refdst;
0120         skb_dst_set_noref(skb, &sch_frag_rt.dst);
0121         IP6CB(skb)->frag_max_size = mru;
0122
0123         ret = ipv6_stub->ipv6_fragment(net, skb->sk, skb,
0124                            sch_frag_xmit);
0125         refdst_drop(orig_dst);
0126     } else {
0127         net_warn_ratelimited("Fail frag %s: eth=%x, MRU=%d, MTU=%d\n",
0128                      netdev_name(skb->dev),
0129                      ntohs(skb_protocol(skb, true)), mru,
0130                      skb->dev->mtu);
0131         goto err;
0132     }
0133
0134     return ret;
0135 err:
0136     kfree_skb(skb);
0137     return ret;
0138 }
0139
0140 int sch_frag_xmit_hook(struct sk_buff *skb, int (*xmit)(struct sk_buff *skb))
0141 {
0142     u16 mru = tc_skb_cb(skb)->mru;
0143     int err;
0144
0145     if (mru && skb->len > mru + skb->dev->hard_header_len)
0146         err = sch_fragment(dev_net(skb->dev), skb, mru, xmit);
0147     else
0148         err = xmit(skb);
0149
0150     return err;
0151 }
0152 EXPORT_SYMBOL_GPL(sch_frag_xmit_hook);