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Merge branch 'l2tp-mtu'

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Guillaume Nault says:

====================
l2tp: sanitise MTU handling on sessions

Most of the code handling sessions' MTU has no effect. The ->mtu field
in struct l2tp_session might be used at session creation time, but
neither PPP nor Ethernet pseudo-wires take updates into account.

L2TP sessions don't have a concept of MTU, which is the reason why
->mtu is mostly ignored. MTU should remain a network device thing.
Therefore this patch set does not try to propagate/update ->mtu to/from
the device. That would complicate the code unnecessarily. Instead this
field and the associated ioctl commands and netlink attributes are
removed.

Patch #1 defines l2tp_tunnel_dst_mtu() in order to simplify the
following patches. Then patches #2 and #3 remove MTU handling from PPP
and Ethernet pseudo-wires respectively.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2018-08-03 10:03:57 -07:00
commit 723a00436a
7 changed files with 47 additions and 87 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/uapi/linux/l2tp.h
View File

@ -119,7 +119,7 @@ enum {
L2TP_ATTR_IP_DADDR, /* u32 */
L2TP_ATTR_UDP_SPORT, /* u16 */
L2TP_ATTR_UDP_DPORT, /* u16 */
L2TP_ATTR_MTU, /* u16 */
L2TP_ATTR_MTU, /* u16 (not used) */
L2TP_ATTR_MRU, /* u16 (not used) */
L2TP_ATTR_STATS, /* nested */
L2TP_ATTR_IP6_SADDR, /* struct in6_addr */

1
net/l2tp/l2tp_core.c
View File

@ -1674,7 +1674,6 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
if (cfg) {
session->pwtype = cfg->pw_type;
session->debug = cfg->debug;
session->mtu = cfg->mtu;
session->send_seq = cfg->send_seq;
session->recv_seq = cfg->recv_seq;
session->lns_mode = cfg->lns_mode;

20
net/l2tp/l2tp_core.h
View File

@ -12,6 +12,9 @@
#ifndef _L2TP_CORE_H_
#define _L2TP_CORE_H_
#include <net/dst.h>
#include <net/sock.h>
/* Just some random numbers */
#define L2TP_TUNNEL_MAGIC 0x42114DDA
#define L2TP_SESSION_MAGIC 0x0C04EB7D
@ -61,7 +64,6 @@ struct l2tp_session_cfg {
int peer_cookie_len; /* 0, 4 or 8 bytes */
int reorder_timeout; /* configured reorder timeout
* (in jiffies) */
int mtu;
char *ifname;
};
@ -105,7 +107,6 @@ struct l2tp_session {
int reorder_timeout; /* configured reorder timeout
* (in jiffies) */
int reorder_skip; /* set if skip to next nr */
int mtu;
enum l2tp_pwtype pwtype;
struct l2tp_stats stats;
struct hlist_node global_hlist; /* Global hash list node */
@ -268,6 +269,21 @@ static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
}
}
static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
{
struct dst_entry *dst;
u32 mtu;
dst = sk_dst_get(tunnel->sock);
if (!dst)
return 0;
mtu = dst_mtu(dst);
dst_release(dst);
return mtu;
}
#define l2tp_printk(ptr, type, func, fmt, ...) \
do { \
if (((ptr)->debug) & (type)) \

3
net/l2tp/l2tp_debugfs.c
View File

@ -191,8 +191,7 @@ static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
if (session->send_seq || session->recv_seq)
seq_printf(m, " nr %hu, ns %hu\n", session->nr, session->ns);
seq_printf(m, " refcnt %d\n", refcount_read(&session->ref_count));
seq_printf(m, " config %d/0/%c/%c/-/%s %08x %u\n",
session->mtu,
seq_printf(m, " config 0/0/%c/%c/-/%s %08x %u\n",
session->recv_seq ? 'R' : '-',
session->send_seq ? 'S' : '-',
session->lns_mode ? "LNS" : "LAC",

25
net/l2tp/l2tp_eth.c
View File

@ -226,22 +226,19 @@ static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
struct net_device *dev)
{
unsigned int overhead = 0;
struct dst_entry *dst;
u32 l3_overhead = 0;
u32 mtu;
/* if the encap is UDP, account for UDP header size */
if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
overhead += sizeof(struct udphdr);
dev->needed_headroom += sizeof(struct udphdr);
}
if (session->mtu != 0) {
dev->mtu = session->mtu;
dev->needed_headroom += session->hdr_len;
return;
}
lock_sock(tunnel->sock);
l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
release_sock(tunnel->sock);
if (l3_overhead == 0) {
/* L3 Overhead couldn't be identified, this could be
* because tunnel->sock was NULL or the socket's
@ -255,18 +252,12 @@ static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
*/
overhead += session->hdr_len + ETH_HLEN + l3_overhead;
/* If PMTU discovery was enabled, use discovered MTU on L2TP device */
dst = sk_dst_get(tunnel->sock);
if (dst) {
/* dst_mtu will use PMTU if found, else fallback to intf MTU */
u32 pmtu = dst_mtu(dst);
mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
if (mtu < dev->min_mtu || mtu > dev->max_mtu)
dev->mtu = ETH_DATA_LEN - overhead;
else
dev->mtu = mtu;
if (pmtu != 0)
dev->mtu = pmtu;
dst_release(dst);
}
session->mtu = dev->mtu - overhead;
dev->mtu = session->mtu;
dev->needed_headroom += session->hdr_len;
}

9
net/l2tp/l2tp_netlink.c
View File

@ -608,9 +608,6 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
cfg.reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
if (info->attrs[L2TP_ATTR_MTU])
cfg.mtu = nla_get_u16(info->attrs[L2TP_ATTR_MTU]);
#ifdef CONFIG_MODULES
if (l2tp_nl_cmd_ops[cfg.pw_type] == NULL) {
genl_unlock();
@ -698,9 +695,6 @@ static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *inf
if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
session->reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
if (info->attrs[L2TP_ATTR_MTU])
session->mtu = nla_get_u16(info->attrs[L2TP_ATTR_MTU]);
ret = l2tp_session_notify(&l2tp_nl_family, info,
session, L2TP_CMD_SESSION_MODIFY);
@ -730,8 +724,7 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int fl
nla_put_u32(skb, L2TP_ATTR_PEER_SESSION_ID,
session->peer_session_id) ||
nla_put_u32(skb, L2TP_ATTR_DEBUG, session->debug) ||
nla_put_u16(skb, L2TP_ATTR_PW_TYPE, session->pwtype) ||
nla_put_u16(skb, L2TP_ATTR_MTU, session->mtu))
nla_put_u16(skb, L2TP_ATTR_PW_TYPE, session->pwtype))
goto nla_put_failure;
if ((session->ifname[0] &&

74
net/l2tp/l2tp_ppp.c
View File

@ -93,7 +93,6 @@
#include <linux/nsproxy.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/dst.h>
#include <net/ip.h>
#include <net/udp.h>
#include <net/xfrm.h>
@ -554,7 +553,6 @@ static void pppol2tp_show(struct seq_file *m, void *arg)
static void pppol2tp_session_init(struct l2tp_session *session)
{
struct pppol2tp_session *ps;
struct dst_entry *dst;
session->recv_skb = pppol2tp_recv;
#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
@ -564,17 +562,6 @@ static void pppol2tp_session_init(struct l2tp_session *session)
ps = l2tp_session_priv(session);
mutex_init(&ps->sk_lock);
ps->owner = current->pid;
/* If PMTU discovery was enabled, use the MTU that was discovered */
dst = sk_dst_get(session->tunnel->sock);
if (dst) {
u32 pmtu = dst_mtu(dst);
if (pmtu)
session->mtu = pmtu - PPPOL2TP_HEADER_OVERHEAD;
dst_release(dst);
}
}
struct l2tp_connect_info {
@ -661,6 +648,22 @@ static int pppol2tp_sockaddr_get_info(const void *sa, int sa_len,
return 0;
}
/* Rough estimation of the maximum payload size a tunnel can transmit without
* fragmenting at the lower IP layer. Assumes L2TPv2 with sequence
* numbers and no IP option. Not quite accurate, but the result is mostly
* unused anyway.
*/
static int pppol2tp_tunnel_mtu(const struct l2tp_tunnel *tunnel)
{
int mtu;
mtu = l2tp_tunnel_dst_mtu(tunnel);
if (mtu <= PPPOL2TP_HEADER_OVERHEAD)
return 1500 - PPPOL2TP_HEADER_OVERHEAD;
return mtu - PPPOL2TP_HEADER_OVERHEAD;
}
/* connect() handler. Attach a PPPoX socket to a tunnel UDP socket
*/
static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
@ -778,8 +781,6 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
goto end;
}
} else {
/* Default MTU must allow space for UDP/L2TP/PPP headers */
cfg.mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
cfg.pw_type = L2TP_PWTYPE_PPP;
session = l2tp_session_create(sizeof(struct pppol2tp_session),
@ -824,7 +825,7 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
po->chan.private = sk;
po->chan.ops = &pppol2tp_chan_ops;
po->chan.mtu = session->mtu;
po->chan.mtu = pppol2tp_tunnel_mtu(tunnel);
error = ppp_register_net_channel(sock_net(sk), &po->chan);
if (error) {
@ -880,10 +881,6 @@ static int pppol2tp_session_create(struct net *net, struct l2tp_tunnel *tunnel,
goto err;
}
/* Default MTU values. */
if (cfg->mtu == 0)
cfg->mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
/* Allocate and initialize a new session context. */
session = l2tp_session_create(sizeof(struct pppol2tp_session),
tunnel, session_id,
@ -1047,7 +1044,6 @@ static void pppol2tp_copy_stats(struct pppol2tp_ioc_stats *dest,
static int pppol2tp_session_ioctl(struct l2tp_session *session,
unsigned int cmd, unsigned long arg)
{
struct ifreq ifr;
int err = 0;
struct sock *sk;
int val = (int) arg;
@ -1063,39 +1059,6 @@ static int pppol2tp_session_ioctl(struct l2tp_session *session,
return -EBADR;
switch (cmd) {
case SIOCGIFMTU:
err = -ENXIO;
if (!(sk->sk_state & PPPOX_CONNECTED))
break;
err = -EFAULT;
if (copy_from_user(&ifr, (void __user *) arg, sizeof(struct ifreq)))
break;
ifr.ifr_mtu = session->mtu;
if (copy_to_user((void __user *) arg, &ifr, sizeof(struct ifreq)))
break;
l2tp_info(session, L2TP_MSG_CONTROL, "%s: get mtu=%d\n",
session->name, session->mtu);
err = 0;
break;
case SIOCSIFMTU:
err = -ENXIO;
if (!(sk->sk_state & PPPOX_CONNECTED))
break;
err = -EFAULT;
if (copy_from_user(&ifr, (void __user *) arg, sizeof(struct ifreq)))
break;
session->mtu = ifr.ifr_mtu;
l2tp_info(session, L2TP_MSG_CONTROL, "%s: set mtu=%d\n",
session->name, session->mtu);
err = 0;
break;
case PPPIOCGMRU:
case PPPIOCGFLAGS:
err = -EFAULT;
@ -1692,8 +1655,7 @@ static void pppol2tp_seq_session_show(struct seq_file *m, void *v)
tunnel->peer_tunnel_id,
session->peer_session_id,
state, user_data_ok);
seq_printf(m, " %d/0/%c/%c/%s %08x %u\n",
session->mtu,
seq_printf(m, " 0/0/%c/%c/%s %08x %u\n",
session->recv_seq ? 'R' : '-',
session->send_seq ? 'S' : '-',
session->lns_mode ? "LNS" : "LAC",