// SPDX-License-Identifier: GPL-2.0
/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* The IP fragmentation functionality.
*
* Authors: Fred N. van Kempen <[email protected]>
* Alan Cox <[email protected]>
*
* Fixes:
* Alan Cox : Split from ip.c , see ip_input.c for history.
* David S. Miller : Begin massive cleanup...
* Andi Kleen : Add sysctls.
* xxxx : Overlapfrag bug.
* Ultima : ip_expire() kernel panic.
* Bill Hawes : Frag accounting and evictor fixes.
* John McDonald : 0 length frag bug.
* Alexey Kuznetsov: SMP races, threading, cleanup.
* Patrick McHardy : LRU queue of frag heads for evictor.
*/
#define pr_fmt(fmt) "IPv4: " fmt
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/jiffies.h>
#include <linux/skbuff.h>
#include <linux/list.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/netdevice.h>
#include <linux/jhash.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <net/route.h>
#include <net/dst.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/checksum.h>
#include <net/inetpeer.h>
#include <net/inet_frag.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/inet.h>
#include <linux/netfilter_ipv4.h>
#include <net/inet_ecn.h>
#include <net/l3mdev.h>
/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
* code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
* as well. Or notify me, at least. --ANK
*/
static const char ip_frag_cache_name[] = "ip4-frags";
/* Describe an entry in the "incomplete datagrams" queue. */
struct ipq {
struct inet_frag_queue q;
u8 ecn; /* RFC3168 support */
u16 max_df_size; /* largest frag with DF set seen */
int iif;
unsigned int rid;
struct inet_peer *peer;
};
static u8 ip4_frag_ecn(u8 tos)
{
return 1 << (tos & INET_ECN_MASK);
}
static struct inet_frags ip4_frags;
static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev);
static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
{
struct ipq *qp = container_of(q, struct ipq, q);
struct net *net = q->fqdir->net;
const struct frag_v4_compare_key *key = a;
q->key.v4 = *key;
qp->ecn = 0;
qp->peer = q->fqdir->max_dist ?
inet_getpeer_v4(net->ipv4.peers, key->saddr, key->vif, 1) :
NULL;
}
static void ip4_frag_free(struct inet_frag_queue *q)
{
struct ipq *qp;
qp = container_of(q, struct ipq, q);
if (qp->peer)
inet_putpeer(qp->peer);
}
/* Destruction primitives. */
static void ipq_put(struct ipq *ipq)
{
inet_frag_put(&ipq->q);
}
/* Kill ipq entry. It is not destroyed immediately,
* because caller (and someone more) holds reference count.
*/
static void ipq_kill(struct ipq *ipq)
{
inet_frag_kill(&ipq->q);
}
static bool frag_expire_skip_icmp(u32 user)
{
return user == IP_DEFRAG_AF_PACKET ||
ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
__IP_DEFRAG_CONNTRACK_IN_END) ||
ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
__IP_DEFRAG_CONNTRACK_BRIDGE_IN);
}
/*
* Oops, a fragment queue timed out. Kill it and send an ICMP reply.
*/
static void ip_expire(struct timer_list *t)
{
struct inet_frag_queue *frag = from_timer(frag, t, timer);
const struct iphdr *iph;
struct sk_buff *head = NULL;
struct net *net;
struct ipq *qp;
int err;
qp = container_of(frag, struct ipq, q);
net = qp->q.fqdir->net;
rcu_read_lock();
/* Paired with WRITE_ONCE() in fqdir_pre_exit(). */
if (READ_ONCE(qp->q.fqdir->dead))
goto out_rcu_unlock;
spin_lock(&qp->q.lock);
if (qp->q.flags & INET_FRAG_COMPLETE)
goto out;
qp->q.flags |= INET_FRAG_DROP;
ipq_kill(qp);
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
__IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
if (!(qp->q.flags & INET_FRAG_FIRST_IN))
goto out;
/* sk_buff::dev and sk_buff::rbnode are unionized. So we
* pull the head out of the tree in order to be able to
* deal with head->dev.
*/
head = inet_frag_pull_head(&qp->q);
if (!head)
goto out;
head->dev = dev_get_by_index_rcu(net, qp->iif);
if (!head->dev)
goto out;
/* skb has no dst, perform route lookup again */
iph = ip_hdr(head);
err = ip_route_input_noref(head, iph->daddr, iph->saddr,
iph->tos, head->dev);
if (err)
goto out;
/* Only an end host needs to send an ICMP
* "Fragment Reassembly Timeout" message, per RFC792.
*/
if (frag_expire_skip_icmp(qp->q.key.v4.user) &&
(skb_rtable(head)->rt_type != RTN_LOCAL))
goto out;
spin_unlock(&qp->q.lock);
icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
goto out_rcu_unlock;
out:
spin_unlock(&qp->q.lock);
out_rcu_unlock:
rcu_read_unlock();
kfree_skb_reason(head, SKB_DROP_REASON_FRAG_REASM_TIMEOUT);
ipq_put(qp);
}
/* Find the correct entry in the "incomplete datagrams" queue for
* this IP datagram, and create new one, if nothing is found.
*/
static struct ipq *ip_find(struct net *net, struct iphdr *iph,
u32 user, int vif)
{
struct frag_v4_compare_key key = {
.saddr = iph->saddr,
.daddr = iph->daddr,
.user = user,
.vif = vif,
.id = iph->id,
.protocol = iph->protocol,
};
struct inet_frag_queue *q;
q = inet_frag_find(net->ipv4.fqdir, &key);
if (!q)
return NULL;
return container_of(q, struct ipq, q);
}
/* Is the fragment too far ahead to be part of ipq? */
static int ip_frag_too_far(struct ipq *qp)
{
struct inet_peer *peer = qp->peer;
unsigned int max = qp->q.fqdir->max_dist;
unsigned int start, end;
int rc;
if (!peer || !max)
return 0;
start = qp->rid;
end = atomic_inc_return(&peer->rid);
qp->rid = end;
rc = qp->q.fragments_tail && (end - start) > max;
if (rc)
__IP_INC_STATS(qp->q.fqdir->net, IPSTATS_MIB_REASMFAILS);
return rc;
}
static int ip_frag_reinit(struct ipq *qp)
{
unsigned int sum_truesize = 0;
if (!mod_timer(&qp->q.timer, jiffies + qp->q.fqdir->timeout)) {
refcount_inc(&qp->q.refcnt);
return -ETIMEDOUT;
}
sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments,
SKB_DROP_REASON_FRAG_TOO_FAR);
sub_frag_mem_limit(qp->q.fqdir, sum_truesize);
qp->q.flags = 0;
qp->q.len = 0;
qp->q.meat = 0;
qp->q.rb_fragments = RB_ROOT;
qp->q.fragments_tail = NULL;
qp->q.last_run_head = NULL;
qp->iif = 0;
qp->ecn = 0;
return 0;
}
/* Add new segment to existing queue. */
static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
{
struct net *net = qp->q.fqdir->net;
int ihl, end, flags, offset;
struct sk_buff *prev_tail;
struct net_device *dev;
unsigned int fragsize;
int err = -ENOENT;
SKB_DR(reason);
u8 ecn;
/* If reassembly is already done, @skb must be a duplicate frag. */
if (qp->q.flags & INET_FRAG_COMPLETE) {
SKB_DR_SET(reason, DUP_FRAG);
goto err;
}
if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
unlikely(ip_frag_too_far(qp)) &&
unlikely(err = ip_frag_reinit(qp))) {
ipq_kill(qp);
goto err;
}
ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
offset = ntohs(ip_hdr(skb)->frag_off);
flags = offset & ~IP_OFFSET;
offset &= IP_OFFSET;
offset <<= 3; /* offset is in 8-byte chunks */
ihl = ip_hdrlen(skb);
/* Determine the position of this fragment. */
end = offset + skb->len - skb_network_offset(skb) - ihl;
err = -EINVAL;
/* Is this the final fragment? */
if ((flags & IP_MF) == 0) {
/* If we already have some bits beyond end
* or have different end, the segment is corrupted.
*/
if (end < qp->q.len ||
((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
goto discard_qp;
qp->q.flags |= INET_FRAG_LAST_IN;
qp->q.len = end;
} else {
if (end&7) {
end &= ~7;
if (skb->ip_summed != CHECKSUM_UNNECESSARY)
skb->ip_summed = CHECKSUM_NONE;
}
if (end > qp->q.len) {
/* Some bits beyond end -> corruption. */
if (qp->q.flags & INET_FRAG_LAST_IN)
goto discard_qp;
qp->q.len = end;
}
}
if (end == offset)
goto discard_qp;
err = -ENOMEM;
if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
goto discard_qp;
err = pskb_trim_rcsum(skb, end - offset);
if (err)
goto discard_qp;
/* Note : skb->rbnode and skb->dev share the same location. */
dev = skb->dev;
/* Makes sure compiler wont do silly aliasing games */
barrier();
prev_tail = qp->q.fragments_tail;
err = inet_frag_queue_insert(&qp->q, skb, offset, end);
if (err)
goto insert_error;
if (dev)
qp->iif = dev->ifindex;
qp->q.stamp = skb->tstamp;
qp->q.tstamp_type = skb->tstamp_type;
qp->q.meat += skb->len;
qp->ecn |= ecn;
add_frag_mem_limit(qp->q.fqdir, skb->truesize);
if (offset == 0)
qp->q.flags |= INET_FRAG_FIRST_IN;
fragsize = skb->len + ihl;
if (fragsize > qp->q.max_size)
qp->q.max_size = fragsize;
if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
fragsize > qp->max_df_size)
qp->max_df_size = fragsize;
if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
qp->q.meat == qp->q.len) {
unsigned long orefdst = skb->_skb_refdst;
skb->_skb_refdst = 0UL;
err = ip_frag_reasm(qp, skb, prev_tail, dev);
skb->_skb_refdst = orefdst;
if (err)
inet_frag_kill(&qp->q);
return err;
}
skb_dst_drop(skb);
skb_orphan(skb);
return -EINPROGRESS;
insert_error:
if (err == IPFRAG_DUP) {
SKB_DR_SET(reason, DUP_FRAG);
err = -EINVAL;
goto err;
}
err = -EINVAL;
__IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
discard_qp:
inet_frag_kill(&qp->q);
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
err:
kfree_skb_reason(skb, reason);
return err;
}
static bool ip_frag_coalesce_ok(const struct ipq *qp)
{
return qp->q.key.v4.user == IP_DEFRAG_LOCAL_DELIVER;
}
/* Build a new IP datagram from all its fragments. */
static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev)
{
struct net *net = qp->q.fqdir->net;
struct iphdr *iph;
void *reasm_data;
int len, err;
u8 ecn;
ipq_kill(qp);
ecn = ip_frag_ecn_table[qp->ecn];
if (unlikely(ecn == 0xff)) {
err = -EINVAL;
goto out_fail;
}
/* Make the one we just received the head. */
reasm_data = inet_frag_reasm_prepare(&qp->q, skb, prev_tail);
if (!reasm_data)
goto out_nomem;
len = ip_hdrlen(skb) + qp->q.len;
err = -E2BIG;
if (len > 65535)
goto out_oversize;
inet_frag_reasm_finish(&qp->q, skb, reasm_data,
ip_frag_coalesce_ok(qp));
skb->dev = dev;
IPCB(skb)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
iph = ip_hdr(skb);
iph->tot_len = htons(len);
iph->tos |= ecn;
/* When we set IP_DF on a refragmented skb we must also force a
* call to ip_fragment to avoid forwarding a DF-skb of size s while
* original sender only sent fragments of size f (where f < s).
*
* We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
* frag seen to avoid sending tiny DF-fragments in case skb was built
* from one very small df-fragment and one large non-df frag.
*/
if (qp->max_df_size == qp->q.max_size) {
IPCB(skb)->flags |= IPSKB_FRAG_PMTU;
iph->frag_off = htons(IP_DF);
} else {
iph->frag_off = 0;
}
ip_send_check(iph);
__IP_INC_STATS(net, IPSTATS_MIB_REASMOKS);
qp->q.rb_fragments = RB_ROOT;
qp->q.fragments_tail = NULL;
qp->q.last_run_head = NULL;
return 0;
out_nomem:
net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
err = -ENOMEM;
goto out_fail;
out_oversize:
net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->q.key.v4.saddr);
out_fail:
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
return err;
}
/* Process an incoming IP datagram fragment. */
int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
{
struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
int vif = l3mdev_master_ifindex_rcu(dev);
struct ipq *qp;
__IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);
/* Lookup (or create) queue header */
qp = ip_find(net, ip_hdr(skb), user, vif);
if (qp) {
int ret;
spin_lock(&qp->q.lock);
ret = ip_frag_queue(qp, skb);
spin_unlock(&qp->q.lock);
ipq_put(qp);
return ret;
}
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
kfree_skb(skb);
return -ENOMEM;
}
EXPORT_SYMBOL(ip_defrag);
struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
{
struct iphdr iph;
int netoff;
u32 len;
if (skb->protocol != htons(ETH_P_IP))
return skb;
netoff = skb_network_offset(skb);
if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
return skb;
if (iph.ihl < 5 || iph.version != 4)
return skb;
len = ntohs(iph.tot_len);
if (skb->len < netoff + len || len < (iph.ihl * 4))
return skb;
if (ip_is_fragment(&iph)) {
skb = skb_share_check(skb, GFP_ATOMIC);
if (skb) {
if (!pskb_may_pull(skb, netoff + iph.ihl * 4)) {
kfree_skb(skb);
return NULL;
}
if (pskb_trim_rcsum(skb, netoff + len)) {
kfree_skb(skb);
return NULL;
}
memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
if (ip_defrag(net, skb, user))
return NULL;
skb_clear_hash(skb);
}
}
return skb;
}
EXPORT_SYMBOL(ip_check_defrag);
#ifdef CONFIG_SYSCTL
static int dist_min;
static struct ctl_table ip4_frags_ns_ctl_table[] = {
{
.procname = "ipfrag_high_thresh",
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
{
.procname = "ipfrag_low_thresh",
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
{
.procname = "ipfrag_time",
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_jiffies,
},
{
.procname = "ipfrag_max_dist",
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &dist_min,
},
};
/* secret interval has been deprecated */
static int ip4_frags_secret_interval_unused;
static struct ctl_table ip4_frags_ctl_table[] = {
{
.procname = "ipfrag_secret_interval",
.data = &ip4_frags_secret_interval_unused,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_jiffies,
},
};
static int __net_init ip4_frags_ns_ctl_register(struct net *net)
{
struct ctl_table *table;
struct ctl_table_header *hdr;
table = ip4_frags_ns_ctl_table;
if (!net_eq(net, &init_net)) {
table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
if (!table)
goto err_alloc;
}
table[0].data = &net->ipv4.fqdir->high_thresh;
table[0].extra1 = &net->ipv4.fqdir->low_thresh;
table[1].data = &net->ipv4.fqdir->low_thresh;
table[1].extra2 = &net->ipv4.fqdir->high_thresh;
table[2].data = &net->ipv4.fqdir->timeout;
table[3].data = &net->ipv4.fqdir->max_dist;
hdr = register_net_sysctl_sz(net, "net/ipv4", table,
ARRAY_SIZE(ip4_frags_ns_ctl_table));
if (!hdr)
goto err_reg;
net->ipv4.frags_hdr = hdr;
return 0;
err_reg:
if (!net_eq(net, &init_net))
kfree(table);
err_alloc:
return -ENOMEM;
}
static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
{
const struct ctl_table *table;
table = net->ipv4.frags_hdr->ctl_table_arg;
unregister_net_sysctl_table(net->ipv4.frags_hdr);
kfree(table);
}
static void __init ip4_frags_ctl_register(void)
{
register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
}
#else
static int ip4_frags_ns_ctl_register(struct net *net)
{
return 0;
}
static void ip4_frags_ns_ctl_unregister(struct net *net)
{
}
static void __init ip4_frags_ctl_register(void)
{
}
#endif
static int __net_init ipv4_frags_init_net(struct net *net)
{
int res;
res = fqdir_init(&net->ipv4.fqdir, &ip4_frags, net);
if (res < 0)
return res;
/* Fragment cache limits.
*
* The fragment memory accounting code, (tries to) account for
* the real memory usage, by measuring both the size of frag
* queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
* and the SKB's truesize.
*
* A 64K fragment consumes 129736 bytes (44*2944)+200
* (1500 truesize == 2944, sizeof(struct ipq) == 200)
*
* We will commit 4MB at one time. Should we cross that limit
* we will prune down to 3MB, making room for approx 8 big 64K
* fragments 8x128k.
*/
net->ipv4.fqdir->high_thresh = 4 * 1024 * 1024;
net->ipv4.fqdir->low_thresh = 3 * 1024 * 1024;
/*
* Important NOTE! Fragment queue must be destroyed before MSL expires.
* RFC791 is wrong proposing to prolongate timer each fragment arrival
* by TTL.
*/
net->ipv4.fqdir->timeout = IP_FRAG_TIME;
net->ipv4.fqdir->max_dist = 64;
res = ip4_frags_ns_ctl_register(net);
if (res < 0)
fqdir_exit(net->ipv4.fqdir);
return res;
}
static void __net_exit ipv4_frags_pre_exit_net(struct net *net)
{
fqdir_pre_exit(net->ipv4.fqdir);
}
static void __net_exit ipv4_frags_exit_net(struct net *net)
{
ip4_frags_ns_ctl_unregister(net);
fqdir_exit(net->ipv4.fqdir);
}
static struct pernet_operations ip4_frags_ops = {
.init = ipv4_frags_init_net,
.pre_exit = ipv4_frags_pre_exit_net,
.exit = ipv4_frags_exit_net,
};
static u32 ip4_key_hashfn(const void *data, u32 len, u32 seed)
{
return jhash2(data,
sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
}
static u32 ip4_obj_hashfn(const void *data, u32 len, u32 seed)
{
const struct inet_frag_queue *fq = data;
return jhash2((const u32 *)&fq->key.v4,
sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
}
static int ip4_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
{
const struct frag_v4_compare_key *key = arg->key;
const struct inet_frag_queue *fq = ptr;
return !!memcmp(&fq->key, key, sizeof(*key));
}
static const struct rhashtable_params ip4_rhash_params = {
.head_offset = offsetof(struct inet_frag_queue, node),
.key_offset = offsetof(struct inet_frag_queue, key),
.key_len = sizeof(struct frag_v4_compare_key),
.hashfn = ip4_key_hashfn,
.obj_hashfn = ip4_obj_hashfn,
.obj_cmpfn = ip4_obj_cmpfn,
.automatic_shrinking = true,
};
void __init ipfrag_init(void)
{
ip4_frags.constructor = ip4_frag_init;
ip4_frags.destructor = ip4_frag_free;
ip4_frags.qsize = sizeof(struct ipq);
ip4_frags.frag_expire = ip_expire;
ip4_frags.frags_cache_name = ip_frag_cache_name;
ip4_frags.rhash_params = ip4_rhash_params;
if (inet_frags_init(&ip4_frags))
panic("IP: failed to allocate ip4_frags cache\n");
ip4_frags_ctl_register();
register_pernet_subsys(&ip4_frags_ops);
}
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