1// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
2#include <linux/if_vlan.h>
3#include <net/netlink.h>
4#include <net/sch_generic.h>
5#include <net/pkt_sched.h>
6#include <net/dst.h>
7#include <net/ip.h>
8#include <net/ip6_fib.h>
9
10struct sch_frag_data {
11	unsigned long dst;
12	struct qdisc_skb_cb cb;
13	__be16 inner_protocol;
14	u16 vlan_tci;
15	__be16 vlan_proto;
16	unsigned int l2_len;
17	u8 l2_data[VLAN_ETH_HLEN];
18	int (*xmit)(struct sk_buff *skb);
19};
20
21static DEFINE_PER_CPU(struct sch_frag_data, sch_frag_data_storage);
22
23static int sch_frag_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
24{
25	struct sch_frag_data *data = this_cpu_ptr(&sch_frag_data_storage);
26
27	if (skb_cow_head(skb, data->l2_len) < 0) {
28		kfree_skb(skb);
29		return -ENOMEM;
30	}
31
32	__skb_dst_copy(skb, data->dst);
33	*qdisc_skb_cb(skb) = data->cb;
34	skb->inner_protocol = data->inner_protocol;
35	if (data->vlan_tci & VLAN_CFI_MASK)
36		__vlan_hwaccel_put_tag(skb, data->vlan_proto,
37				       data->vlan_tci & ~VLAN_CFI_MASK);
38	else
39		__vlan_hwaccel_clear_tag(skb);
40
41	/* Reconstruct the MAC header.  */
42	skb_push(skb, data->l2_len);
43	memcpy(skb->data, &data->l2_data, data->l2_len);
44	skb_postpush_rcsum(skb, skb->data, data->l2_len);
45	skb_reset_mac_header(skb);
46
47	return data->xmit(skb);
48}
49
50static void sch_frag_prepare_frag(struct sk_buff *skb,
51				  int (*xmit)(struct sk_buff *skb))
52{
53	unsigned int hlen = skb_network_offset(skb);
54	struct sch_frag_data *data;
55
56	data = this_cpu_ptr(&sch_frag_data_storage);
57	data->dst = skb->_skb_refdst;
58	data->cb = *qdisc_skb_cb(skb);
59	data->xmit = xmit;
60	data->inner_protocol = skb->inner_protocol;
61	if (skb_vlan_tag_present(skb))
62		data->vlan_tci = skb_vlan_tag_get(skb) | VLAN_CFI_MASK;
63	else
64		data->vlan_tci = 0;
65	data->vlan_proto = skb->vlan_proto;
66	data->l2_len = hlen;
67	memcpy(&data->l2_data, skb->data, hlen);
68
69	memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
70	skb_pull(skb, hlen);
71}
72
73static unsigned int
74sch_frag_dst_get_mtu(const struct dst_entry *dst)
75{
76	return dst->dev->mtu;
77}
78
79static struct dst_ops sch_frag_dst_ops = {
80	.family = AF_UNSPEC,
81	.mtu = sch_frag_dst_get_mtu,
82};
83
84static int sch_fragment(struct net *net, struct sk_buff *skb,
85			u16 mru, int (*xmit)(struct sk_buff *skb))
86{
87	int ret = -1;
88
89	if (skb_network_offset(skb) > VLAN_ETH_HLEN) {
90		net_warn_ratelimited("L2 header too long to fragment\n");
91		goto err;
92	}
93
94	if (skb_protocol(skb, true) == htons(ETH_P_IP)) {
95		struct rtable sch_frag_rt = { 0 };
96		unsigned long orig_dst;
97
98		sch_frag_prepare_frag(skb, xmit);
99		dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL,
100			 DST_OBSOLETE_NONE, DST_NOCOUNT);
101		sch_frag_rt.dst.dev = skb->dev;
102
103		orig_dst = skb->_skb_refdst;
104		skb_dst_set_noref(skb, &sch_frag_rt.dst);
105		IPCB(skb)->frag_max_size = mru;
106
107		ret = ip_do_fragment(net, skb->sk, skb, sch_frag_xmit);
108		refdst_drop(orig_dst);
109	} else if (skb_protocol(skb, true) == htons(ETH_P_IPV6)) {
110		unsigned long orig_dst;
111		struct rt6_info sch_frag_rt;
112
113		sch_frag_prepare_frag(skb, xmit);
114		memset(&sch_frag_rt, 0, sizeof(sch_frag_rt));
115		dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL,
116			 DST_OBSOLETE_NONE, DST_NOCOUNT);
117		sch_frag_rt.dst.dev = skb->dev;
118
119		orig_dst = skb->_skb_refdst;
120		skb_dst_set_noref(skb, &sch_frag_rt.dst);
121		IP6CB(skb)->frag_max_size = mru;
122
123		ret = ipv6_stub->ipv6_fragment(net, skb->sk, skb,
124					       sch_frag_xmit);
125		refdst_drop(orig_dst);
126	} else {
127		net_warn_ratelimited("Fail frag %s: eth=%x, MRU=%d, MTU=%d\n",
128				     netdev_name(skb->dev),
129				     ntohs(skb_protocol(skb, true)), mru,
130				     skb->dev->mtu);
131		goto err;
132	}
133
134	return ret;
135err:
136	kfree_skb(skb);
137	return ret;
138}
139
140int sch_frag_xmit_hook(struct sk_buff *skb, int (*xmit)(struct sk_buff *skb))
141{
142	u16 mru = tc_skb_cb(skb)->mru;
143	int err;
144
145	if (mru && skb->len > mru + skb->dev->hard_header_len)
146		err = sch_fragment(dev_net(skb->dev), skb, mru, xmit);
147	else
148		err = xmit(skb);
149
150	return err;
151}
152EXPORT_SYMBOL_GPL(sch_frag_xmit_hook);
153