diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
commit | 2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch) | |
tree | 848558de17fb3008cdf4d861b01ac7781903ce39 /net/ipv4/ip_fragment.c | |
parent | Initial commit. (diff) | |
download | linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip |
Adding upstream version 6.1.76.upstream/6.1.76upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | net/ipv4/ip_fragment.c | 753 |
1 files changed, 753 insertions, 0 deletions
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c new file mode 100644 index 000000000..fb1535698 --- /dev/null +++ b/net/ipv4/ip_fragment.c @@ -0,0 +1,753 @@ +// 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 <waltje@uWalt.NL.Mugnet.ORG> + * Alan Cox <alan@lxorguk.ukuu.org.uk> + * + * 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; + + 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(head); + 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); + 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; + u8 ecn; + + if (qp->q.flags & INET_FRAG_COMPLETE) + 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.mono_delivery_time = skb->mono_delivery_time; + 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); + return -EINPROGRESS; + +insert_error: + if (err == IPFRAG_DUP) { + kfree_skb(skb); + return -EINVAL; + } + 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(skb); + 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); + skb_orphan(skb); + + /* 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(net, "net/ipv4", 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) +{ + 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); +} |