// SPDX-License-Identifier: GPL-2.0-or-later
/* 6LoWPAN fragment reassembly
*
* Authors:
* Alexander Aring <[email protected]>
*
* Based on: net/ipv6/reassembly.c
*/
#define pr_fmt(fmt) "6LoWPAN: " fmt
#include <linux/net.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <net/ieee802154_netdev.h>
#include <net/6lowpan.h>
#include <net/ipv6_frag.h>
#include <net/inet_frag.h>
#include <net/ip.h>
#include "6lowpan_i.h"
static const char lowpan_frags_cache_name[] = "lowpan-frags";
static struct inet_frags lowpan_frags;
static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev, struct net_device *ldev);
static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
{
const struct frag_lowpan_compare_key *key = a;
BUILD_BUG_ON(sizeof(*key) > sizeof(q->key));
memcpy(&q->key, key, sizeof(*key));
}
static void lowpan_frag_expire(struct timer_list *t)
{
struct inet_frag_queue *frag = from_timer(frag, t, timer);
struct frag_queue *fq;
fq = container_of(frag, struct frag_queue, q);
spin_lock(&fq->q.lock);
if (fq->q.flags & INET_FRAG_COMPLETE)
goto out;
inet_frag_kill(&fq->q);
out:
spin_unlock(&fq->q.lock);
inet_frag_put(&fq->q);
}
static inline struct lowpan_frag_queue *
fq_find(struct net *net, const struct lowpan_802154_cb *cb,
const struct ieee802154_addr *src,
const struct ieee802154_addr *dst)
{
struct netns_ieee802154_lowpan *ieee802154_lowpan =
net_ieee802154_lowpan(net);
struct frag_lowpan_compare_key key = {};
struct inet_frag_queue *q;
key.tag = cb->d_tag;
key.d_size = cb->d_size;
key.src = *src;
key.dst = *dst;
q = inet_frag_find(ieee802154_lowpan->fqdir, &key);
if (!q)
return NULL;
return container_of(q, struct lowpan_frag_queue, q);
}
static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
struct sk_buff *skb, u8 frag_type)
{
struct sk_buff *prev_tail;
struct net_device *ldev;
int end, offset, err;
/* inet_frag_queue_* functions use skb->cb; see struct ipfrag_skb_cb
* in inet_fragment.c
*/
BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(struct inet_skb_parm));
BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(struct inet6_skb_parm));
if (fq->q.flags & INET_FRAG_COMPLETE)
goto err;
offset = lowpan_802154_cb(skb)->d_offset << 3;
end = lowpan_802154_cb(skb)->d_size;
/* Is this the final fragment? */
if (offset + skb->len == end) {
/* If we already have some bits beyond end
* or have different end, the segment is corrupted.
*/
if (end < fq->q.len ||
((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
goto err;
fq->q.flags |= INET_FRAG_LAST_IN;
fq->q.len = end;
} else {
if (end > fq->q.len) {
/* Some bits beyond end -> corruption. */
if (fq->q.flags & INET_FRAG_LAST_IN)
goto err;
fq->q.len = end;
}
}
ldev = skb->dev;
if (ldev)
skb->dev = NULL;
barrier();
prev_tail = fq->q.fragments_tail;
err = inet_frag_queue_insert(&fq->q, skb, offset, end);
if (err)
goto err;
fq->q.stamp = skb->tstamp;
fq->q.tstamp_type = skb->tstamp_type;
if (frag_type == LOWPAN_DISPATCH_FRAG1)
fq->q.flags |= INET_FRAG_FIRST_IN;
fq->q.meat += skb->len;
add_frag_mem_limit(fq->q.fqdir, skb->truesize);
if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
fq->q.meat == fq->q.len) {
int res;
unsigned long orefdst = skb->_skb_refdst;
skb->_skb_refdst = 0UL;
res = lowpan_frag_reasm(fq, skb, prev_tail, ldev);
skb->_skb_refdst = orefdst;
return res;
}
skb_dst_drop(skb);
return -1;
err:
kfree_skb(skb);
return -1;
}
/* Check if this packet is complete.
*
* It is called with locked fq, and caller must check that
* queue is eligible for reassembly i.e. it is not COMPLETE,
* the last and the first frames arrived and all the bits are here.
*/
static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *ldev)
{
void *reasm_data;
inet_frag_kill(&fq->q);
reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
if (!reasm_data)
goto out_oom;
inet_frag_reasm_finish(&fq->q, skb, reasm_data, false);
skb->dev = ldev;
skb->tstamp = fq->q.stamp;
fq->q.rb_fragments = RB_ROOT;
fq->q.fragments_tail = NULL;
fq->q.last_run_head = NULL;
return 1;
out_oom:
net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
return -1;
}
static int lowpan_frag_rx_handlers_result(struct sk_buff *skb,
lowpan_rx_result res)
{
switch (res) {
case RX_QUEUED:
return NET_RX_SUCCESS;
case RX_CONTINUE:
/* nobody cared about this packet */
net_warn_ratelimited("%s: received unknown dispatch\n",
__func__);
fallthrough;
default:
/* all others failure */
return NET_RX_DROP;
}
}
static lowpan_rx_result lowpan_frag_rx_h_iphc(struct sk_buff *skb)
{
int ret;
if (!lowpan_is_iphc(*skb_network_header(skb)))
return RX_CONTINUE;
ret = lowpan_iphc_decompress(skb);
if (ret < 0)
return RX_DROP;
return RX_QUEUED;
}
static int lowpan_invoke_frag_rx_handlers(struct sk_buff *skb)
{
lowpan_rx_result res;
#define CALL_RXH(rxh) \
do { \
res = rxh(skb); \
if (res != RX_CONTINUE) \
goto rxh_next; \
} while (0)
/* likely at first */
CALL_RXH(lowpan_frag_rx_h_iphc);
CALL_RXH(lowpan_rx_h_ipv6);
rxh_next:
return lowpan_frag_rx_handlers_result(skb, res);
#undef CALL_RXH
}
#define LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK 0x07
#define LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT 8
static int lowpan_get_cb(struct sk_buff *skb, u8 frag_type,
struct lowpan_802154_cb *cb)
{
bool fail;
u8 high = 0, low = 0;
__be16 d_tag = 0;
fail = lowpan_fetch_skb(skb, &high, 1);
fail |= lowpan_fetch_skb(skb, &low, 1);
/* remove the dispatch value and use first three bits as high value
* for the datagram size
*/
cb->d_size = (high & LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK) <<
LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT | low;
fail |= lowpan_fetch_skb(skb, &d_tag, 2);
cb->d_tag = ntohs(d_tag);
if (frag_type == LOWPAN_DISPATCH_FRAGN) {
fail |= lowpan_fetch_skb(skb, &cb->d_offset, 1);
} else {
skb_reset_network_header(skb);
cb->d_offset = 0;
/* check if datagram_size has ipv6hdr on FRAG1 */
fail |= cb->d_size < sizeof(struct ipv6hdr);
/* check if we can dereference the dispatch value */
fail |= !skb->len;
}
if (unlikely(fail))
return -EIO;
return 0;
}
int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
{
struct lowpan_frag_queue *fq;
struct net *net = dev_net(skb->dev);
struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
struct ieee802154_hdr hdr = {};
int err;
if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
goto err;
err = lowpan_get_cb(skb, frag_type, cb);
if (err < 0)
goto err;
if (frag_type == LOWPAN_DISPATCH_FRAG1) {
err = lowpan_invoke_frag_rx_handlers(skb);
if (err == NET_RX_DROP)
goto err;
}
if (cb->d_size > IPV6_MIN_MTU) {
net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
goto err;
}
fq = fq_find(net, cb, &hdr.source, &hdr.dest);
if (fq != NULL) {
int ret;
spin_lock(&fq->q.lock);
ret = lowpan_frag_queue(fq, skb, frag_type);
spin_unlock(&fq->q.lock);
inet_frag_put(&fq->q);
return ret;
}
err:
kfree_skb(skb);
return -1;
}
#ifdef CONFIG_SYSCTL
static struct ctl_table lowpan_frags_ns_ctl_table[] = {
{
.procname = "6lowpanfrag_high_thresh",
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
{
.procname = "6lowpanfrag_low_thresh",
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
{
.procname = "6lowpanfrag_time",
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_jiffies,
},
};
/* secret interval has been deprecated */
static int lowpan_frags_secret_interval_unused;
static struct ctl_table lowpan_frags_ctl_table[] = {
{
.procname = "6lowpanfrag_secret_interval",
.data = &lowpan_frags_secret_interval_unused,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_jiffies,
},
};
static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
{
struct ctl_table *table;
struct ctl_table_header *hdr;
struct netns_ieee802154_lowpan *ieee802154_lowpan =
net_ieee802154_lowpan(net);
size_t table_size = ARRAY_SIZE(lowpan_frags_ns_ctl_table);
table = lowpan_frags_ns_ctl_table;
if (!net_eq(net, &init_net)) {
table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
GFP_KERNEL);
if (table == NULL)
goto err_alloc;
/* Don't export sysctls to unprivileged users */
if (net->user_ns != &init_user_ns)
table_size = 0;
}
table[0].data = &ieee802154_lowpan->fqdir->high_thresh;
table[0].extra1 = &ieee802154_lowpan->fqdir->low_thresh;
table[1].data = &ieee802154_lowpan->fqdir->low_thresh;
table[1].extra2 = &ieee802154_lowpan->fqdir->high_thresh;
table[2].data = &ieee802154_lowpan->fqdir->timeout;
hdr = register_net_sysctl_sz(net, "net/ieee802154/6lowpan", table,
table_size);
if (hdr == NULL)
goto err_reg;
ieee802154_lowpan->sysctl.frags_hdr = hdr;
return 0;
err_reg:
if (!net_eq(net, &init_net))
kfree(table);
err_alloc:
return -ENOMEM;
}
static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
{
const struct ctl_table *table;
struct netns_ieee802154_lowpan *ieee802154_lowpan =
net_ieee802154_lowpan(net);
table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
if (!net_eq(net, &init_net))
kfree(table);
}
static struct ctl_table_header *lowpan_ctl_header;
static int __init lowpan_frags_sysctl_register(void)
{
lowpan_ctl_header = register_net_sysctl(&init_net,
"net/ieee802154/6lowpan",
lowpan_frags_ctl_table);
return lowpan_ctl_header == NULL ? -ENOMEM : 0;
}
static void lowpan_frags_sysctl_unregister(void)
{
unregister_net_sysctl_table(lowpan_ctl_header);
}
#else
static inline int lowpan_frags_ns_sysctl_register(struct net *net)
{
return 0;
}
static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
{
}
static inline int __init lowpan_frags_sysctl_register(void)
{
return 0;
}
static inline void lowpan_frags_sysctl_unregister(void)
{
}
#endif
static int __net_init lowpan_frags_init_net(struct net *net)
{
struct netns_ieee802154_lowpan *ieee802154_lowpan =
net_ieee802154_lowpan(net);
int res;
res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags, net);
if (res < 0)
return res;
ieee802154_lowpan->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
ieee802154_lowpan->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
ieee802154_lowpan->fqdir->timeout = IPV6_FRAG_TIMEOUT;
res = lowpan_frags_ns_sysctl_register(net);
if (res < 0)
fqdir_exit(ieee802154_lowpan->fqdir);
return res;
}
static void __net_exit lowpan_frags_pre_exit_net(struct net *net)
{
struct netns_ieee802154_lowpan *ieee802154_lowpan =
net_ieee802154_lowpan(net);
fqdir_pre_exit(ieee802154_lowpan->fqdir);
}
static void __net_exit lowpan_frags_exit_net(struct net *net)
{
struct netns_ieee802154_lowpan *ieee802154_lowpan =
net_ieee802154_lowpan(net);
lowpan_frags_ns_sysctl_unregister(net);
fqdir_exit(ieee802154_lowpan->fqdir);
}
static struct pernet_operations lowpan_frags_ops = {
.init = lowpan_frags_init_net,
.pre_exit = lowpan_frags_pre_exit_net,
.exit = lowpan_frags_exit_net,
};
static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)
{
return jhash2(data,
sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
}
static u32 lowpan_obj_hashfn(const void *data, u32 len, u32 seed)
{
const struct inet_frag_queue *fq = data;
return jhash2((const u32 *)&fq->key,
sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
}
static int lowpan_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
{
const struct frag_lowpan_compare_key *key = arg->key;
const struct inet_frag_queue *fq = ptr;
return !!memcmp(&fq->key, key, sizeof(*key));
}
static const struct rhashtable_params lowpan_rhash_params = {
.head_offset = offsetof(struct inet_frag_queue, node),
.hashfn = lowpan_key_hashfn,
.obj_hashfn = lowpan_obj_hashfn,
.obj_cmpfn = lowpan_obj_cmpfn,
.automatic_shrinking = true,
};
int __init lowpan_net_frag_init(void)
{
int ret;
lowpan_frags.constructor = lowpan_frag_init;
lowpan_frags.destructor = NULL;
lowpan_frags.qsize = sizeof(struct frag_queue);
lowpan_frags.frag_expire = lowpan_frag_expire;
lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
lowpan_frags.rhash_params = lowpan_rhash_params;
ret = inet_frags_init(&lowpan_frags);
if (ret)
goto out;
ret = lowpan_frags_sysctl_register();
if (ret)
goto err_sysctl;
ret = register_pernet_subsys(&lowpan_frags_ops);
if (ret)
goto err_pernet;
out:
return ret;
err_pernet:
lowpan_frags_sysctl_unregister();
err_sysctl:
inet_frags_fini(&lowpan_frags);
return ret;
}
void lowpan_net_frag_exit(void)
{
lowpan_frags_sysctl_unregister();
unregister_pernet_subsys(&lowpan_frags_ops);
inet_frags_fini(&lowpan_frags);
}
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