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/*
* Stream Parser
*
* Copyright (c) 2016 Tom Herbert <tom@herbertland.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*/
#include <linux/bpf.h>
#include <linux/errno.h>
#include <linux/errqueue.h>
#include <linux/file.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/poll.h>
#include <linux/rculist.h>
#include <linux/skbuff.h>
#include <linux/socket.h>
#include <linux/uaccess.h>
#include <linux/workqueue.h>
#include <net/strparser.h>
#include <net/netns/generic.h>
#include <net/sock.h>
static struct workqueue_struct *strp_wq;
struct _strp_msg {
/* Internal cb structure. struct strp_msg must be first for passing
* to upper layer.
*/
struct strp_msg strp;
int accum_len;
};
static inline struct _strp_msg *_strp_msg(struct sk_buff *skb)
{
return (struct _strp_msg *)((void *)skb->cb +
offsetof(struct qdisc_skb_cb, data));
}
/* Lower lock held */
static void strp_abort_strp(struct strparser *strp, int err)
{
/* Unrecoverable error in receive */
cancel_delayed_work(&strp->msg_timer_work);
if (strp->stopped)
return;
strp->stopped = 1;
if (strp->sk) {
struct sock *sk = strp->sk;
/* Report an error on the lower socket */
sk->sk_err = -err;
sk->sk_error_report(sk);
}
}
static void strp_start_timer(struct strparser *strp, long timeo)
{
if (timeo && timeo != LONG_MAX)
mod_delayed_work(strp_wq, &strp->msg_timer_work, timeo);
}
/* Lower lock held */
static void strp_parser_err(struct strparser *strp, int err,
read_descriptor_t *desc)
{
desc->error = err;
kfree_skb(strp->skb_head);
strp->skb_head = NULL;
strp->cb.abort_parser(strp, err);
}
static inline int strp_peek_len(struct strparser *strp)
{
if (strp->sk) {
struct socket *sock = strp->sk->sk_socket;
return sock->ops->peek_len(sock);
}
/* If we don't have an associated socket there's nothing to peek.
* Return int max to avoid stopping the strparser.
*/
return INT_MAX;
}
/* Lower socket lock held */
static int __strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
unsigned int orig_offset, size_t orig_len,
size_t max_msg_size, long timeo)
{
struct strparser *strp = (struct strparser *)desc->arg.data;
struct _strp_msg *stm;
struct sk_buff *head, *skb;
size_t eaten = 0, cand_len;
ssize_t extra;
int err;
bool cloned_orig = false;
if (strp->paused)
return 0;
head = strp->skb_head;
if (head) {
/* Message already in progress */
if (unlikely(orig_offset)) {
/* Getting data with a non-zero offset when a message is
* in progress is not expected. If it does happen, we
* need to clone and pull since we can't deal with
* offsets in the skbs for a message expect in the head.
*/
orig_skb = skb_clone(orig_skb, GFP_ATOMIC);
if (!orig_skb) {
STRP_STATS_INCR(strp->stats.mem_fail);
desc->error = -ENOMEM;
return 0;
}
if (!pskb_pull(orig_skb, orig_offset)) {
STRP_STATS_INCR(strp->stats.mem_fail);
kfree_skb(orig_skb);
desc->error = -ENOMEM;
return 0;
}
cloned_orig = true;
orig_offset = 0;
}
if (!strp->skb_nextp) {
/* We are going to append to the frags_list of head.
* Need to unshare the frag_list.
*/
err = skb_unclone(head, GFP_ATOMIC);
if (err) {
STRP_STATS_INCR(strp->stats.mem_fail);
desc->error = err;
return 0;
}
if (unlikely(skb_shinfo(head)->frag_list)) {
/* We can't append to an sk_buff that already
* has a frag_list. We create a new head, point
* the frag_list of that to the old head, and
* then are able to use the old head->next for
* appending to the message.
*/
if (WARN_ON(head->next)) {
desc->error = -EINVAL;
return 0;
}
skb = alloc_skb(0, GFP_ATOMIC);
if (!skb) {
STRP_STATS_INCR(strp->stats.mem_fail);
desc->error = -ENOMEM;
return 0;
}
skb->len = head->len;
skb->data_len = head->len;
skb->truesize = head->truesize;
*_strp_msg(skb) = *_strp_msg(head);
strp->skb_nextp = &head->next;
skb_shinfo(skb)->frag_list = head;
strp->skb_head = skb;
head = skb;
} else {
strp->skb_nextp =
&skb_shinfo(head)->frag_list;
}
}
}
while (eaten < orig_len) {
/* Always clone since we will consume something */
skb = skb_clone(orig_skb, GFP_ATOMIC);
if (!skb) {
STRP_STATS_INCR(strp->stats.mem_fail);
desc->error = -ENOMEM;
break;
}
cand_len = orig_len - eaten;
head = strp->skb_head;
if (!head) {
head = skb;
strp->skb_head = head;
/* Will set skb_nextp on next packet if needed */
strp->skb_nextp = NULL;
stm = _strp_msg(head);
memset(stm, 0, sizeof(*stm));
stm->strp.offset = orig_offset + eaten;
} else {
/* Unclone if we are appending to an skb that we
* already share a frag_list with.
*/
if (skb_has_frag_list(skb)) {
err = skb_unclone(skb, GFP_ATOMIC);
if (err) {
STRP_STATS_INCR(strp->stats.mem_fail);
desc->error = err;
break;
}
}
stm = _strp_msg(head);
*strp->skb_nextp = skb;
strp->skb_nextp = &skb->next;
head->data_len += skb->len;
head->len += skb->len;
head->truesize += skb->truesize;
}
if (!stm->strp.full_len) {
ssize_t len;
len = (*strp->cb.parse_msg)(strp, head);
if (!len) {
/* Need more header to determine length */
if (!stm->accum_len) {
/* Start RX timer for new message */
strp_start_timer(strp, timeo);
}
stm->accum_len += cand_len;
eaten += cand_len;
STRP_STATS_INCR(strp->stats.need_more_hdr);
WARN_ON(eaten != orig_len);
break;
} else if (len < 0) {
if (len == -ESTRPIPE && stm->accum_len) {
len = -ENODATA;
strp->unrecov_intr = 1;
} else {
strp->interrupted = 1;
}
strp_parser_err(strp, len, desc);
break;
} else if (len > max_msg_size) {
/* Message length exceeds maximum allowed */
STRP_STATS_INCR(strp->stats.msg_too_big);
strp_parser_err(strp, -EMSGSIZE, desc);
break;
} else if (len <= (ssize_t)head->len -
skb->len - stm->strp.offset) {
/* Length must be into new skb (and also
* greater than zero)
*/
STRP_STATS_INCR(strp->stats.bad_hdr_len);
strp_parser_err(strp, -EPROTO, desc);
break;
}
stm->strp.full_len = len;
}
extra = (ssize_t)(stm->accum_len + cand_len) -
stm->strp.full_len;
if (extra < 0) {
/* Message not complete yet. */
if (stm->strp.full_len - stm->accum_len >
strp_peek_len(strp)) {
/* Don't have the whole message in the socket
* buffer. Set strp->need_bytes to wait for
* the rest of the message. Also, set "early
* eaten" since we've already buffered the skb
* but don't consume yet per strp_read_sock.
*/
if (!stm->accum_len) {
/* Start RX timer for new message */
strp_start_timer(strp, timeo);
}
stm->accum_len += cand_len;
eaten += cand_len;
strp->need_bytes = stm->strp.full_len -
stm->accum_len;
STRP_STATS_ADD(strp->stats.bytes, cand_len);
desc->count = 0; /* Stop reading socket */
break;
}
stm->accum_len += cand_len;
eaten += cand_len;
WARN_ON(eaten != orig_len);
break;
}
/* Positive extra indicates more bytes than needed for the
* message
*/
WARN_ON(extra > cand_len);
eaten += (cand_len - extra);
/* Hurray, we have a new message! */
cancel_delayed_work(&strp->msg_timer_work);
strp->skb_head = NULL;
strp->need_bytes = 0;
STRP_STATS_INCR(strp->stats.msgs);
/* Give skb to upper layer */
strp->cb.rcv_msg(strp, head);
if (unlikely(strp->paused)) {
/* Upper layer paused strp */
break;
}
}
if (cloned_orig)
kfree_skb(orig_skb);
STRP_STATS_ADD(strp->stats.bytes, eaten);
return eaten;
}
int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
unsigned int orig_offset, size_t orig_len,
size_t max_msg_size, long timeo)
{
read_descriptor_t desc; /* Dummy arg to strp_recv */
desc.arg.data = strp;
return __strp_recv(&desc, orig_skb, orig_offset, orig_len,
max_msg_size, timeo);
}
EXPORT_SYMBOL_GPL(strp_process);
static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
unsigned int orig_offset, size_t orig_len)
{
struct strparser *strp = (struct strparser *)desc->arg.data;
return __strp_recv(desc, orig_skb, orig_offset, orig_len,
strp->sk->sk_rcvbuf, strp->sk->sk_rcvtimeo);
}
static int default_read_sock_done(struct strparser *strp, int err)
{
return err;
}
/* Called with lock held on lower socket */
static int strp_read_sock(struct strparser *strp)
{
struct socket *sock = strp->sk->sk_socket;
read_descriptor_t desc;
if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
return -EBUSY;
desc.arg.data = strp;
desc.error = 0;
desc.count = 1; /* give more than one skb per call */
/* sk should be locked here, so okay to do read_sock */
sock->ops->read_sock(strp->sk, &desc, strp_recv);
desc.error = strp->cb.read_sock_done(strp, desc.error);
return desc.error;
}
/* Lower sock lock held */
void strp_data_ready(struct strparser *strp)
{
if (unlikely(strp->stopped) || strp->paused)
return;
/* This check is needed to synchronize with do_strp_work.
* do_strp_work acquires a process lock (lock_sock) whereas
* the lock held here is bh_lock_sock. The two locks can be
* held by different threads at the same time, but bh_lock_sock
* allows a thread in BH context to safely check if the process
* lock is held. In this case, if the lock is held, queue work.
*/
if (sock_owned_by_user_nocheck(strp->sk)) {
queue_work(strp_wq, &strp->work);
return;
}
if (strp->need_bytes) {
if (strp_peek_len(strp) < strp->need_bytes)
return;
}
if (strp_read_sock(strp) == -ENOMEM)
queue_work(strp_wq, &strp->work);
}
EXPORT_SYMBOL_GPL(strp_data_ready);
static void do_strp_work(struct strparser *strp)
{
/* We need the read lock to synchronize with strp_data_ready. We
* need the socket lock for calling strp_read_sock.
*/
strp->cb.lock(strp);
if (unlikely(strp->stopped))
goto out;
if (strp->paused)
goto out;
if (strp_read_sock(strp) == -ENOMEM)
queue_work(strp_wq, &strp->work);
out:
strp->cb.unlock(strp);
}
static void strp_work(struct work_struct *w)
{
do_strp_work(container_of(w, struct strparser, work));
}
static void strp_msg_timeout(struct work_struct *w)
{
struct strparser *strp = container_of(w, struct strparser,
msg_timer_work.work);
/* Message assembly timed out */
STRP_STATS_INCR(strp->stats.msg_timeouts);
strp->cb.lock(strp);
strp->cb.abort_parser(strp, -ETIMEDOUT);
strp->cb.unlock(strp);
}
static void strp_sock_lock(struct strparser *strp)
{
lock_sock(strp->sk);
}
static void strp_sock_unlock(struct strparser *strp)
{
release_sock(strp->sk);
}
int strp_init(struct strparser *strp, struct sock *sk,
const struct strp_callbacks *cb)
{
if (!cb || !cb->rcv_msg || !cb->parse_msg)
return -EINVAL;
/* The sk (sock) arg determines the mode of the stream parser.
*
* If the sock is set then the strparser is in receive callback mode.
* The upper layer calls strp_data_ready to kick receive processing
* and strparser calls the read_sock function on the socket to
* get packets.
*
* If the sock is not set then the strparser is in general mode.
* The upper layer calls strp_process for each skb to be parsed.
*/
if (!sk) {
if (!cb->lock || !cb->unlock)
return -EINVAL;
}
memset(strp, 0, sizeof(*strp));
strp->sk = sk;
strp->cb.lock = cb->lock ? : strp_sock_lock;
strp->cb.unlock = cb->unlock ? : strp_sock_unlock;
strp->cb.rcv_msg = cb->rcv_msg;
strp->cb.parse_msg = cb->parse_msg;
strp->cb.read_sock_done = cb->read_sock_done ? : default_read_sock_done;
strp->cb.abort_parser = cb->abort_parser ? : strp_abort_strp;
INIT_DELAYED_WORK(&strp->msg_timer_work, strp_msg_timeout);
INIT_WORK(&strp->work, strp_work);
return 0;
}
EXPORT_SYMBOL_GPL(strp_init);
/* Sock process lock held (lock_sock) */
void __strp_unpause(struct strparser *strp)
{
strp->paused = 0;
if (strp->need_bytes) {
if (strp_peek_len(strp) < strp->need_bytes)
return;
}
strp_read_sock(strp);
}
EXPORT_SYMBOL_GPL(__strp_unpause);
void strp_unpause(struct strparser *strp)
{
strp->paused = 0;
/* Sync setting paused with RX work */
smp_mb();
queue_work(strp_wq, &strp->work);
}
EXPORT_SYMBOL_GPL(strp_unpause);
/* strp must already be stopped so that strp_recv will no longer be called.
* Note that strp_done is not called with the lower socket held.
*/
void strp_done(struct strparser *strp)
{
WARN_ON(!strp->stopped);
cancel_delayed_work_sync(&strp->msg_timer_work);
cancel_work_sync(&strp->work);
if (strp->skb_head) {
kfree_skb(strp->skb_head);
strp->skb_head = NULL;
}
}
EXPORT_SYMBOL_GPL(strp_done);
void strp_stop(struct strparser *strp)
{
strp->stopped = 1;
}
EXPORT_SYMBOL_GPL(strp_stop);
void strp_check_rcv(struct strparser *strp)
{
queue_work(strp_wq, &strp->work);
}
EXPORT_SYMBOL_GPL(strp_check_rcv);
static int __init strp_mod_init(void)
{
strp_wq = create_singlethread_workqueue("kstrp");
if (unlikely(!strp_wq))
return -ENOMEM;
return 0;
}
static void __exit strp_mod_exit(void)
{
destroy_workqueue(strp_wq);
}
module_init(strp_mod_init);
module_exit(strp_mod_exit);
MODULE_LICENSE("GPL");
|