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authorGuillaume Nault <g.nault@alphalink.fr>2018-08-03 12:38:37 +0200
committerDavid S. Miller <davem@davemloft.net>2018-08-03 10:03:57 -0700
commit789141b215fc509defdd0f0978e4bf1bb5b31fc2 (patch)
treed78ce6506f81efcf2ab0bd54d4698fa2e077e632
parent1f5cd2a0107d4ed95cbd9118e6a5f7ccd3d4d12a (diff)
downloadlinux-789141b215fc509defdd0f0978e4bf1bb5b31fc2.tar.bz2
l2tp: simplify MTU handling in l2tp_ppp
The value of the session's .mtu field, as defined by pppol2tp_connect() or pppol2tp_session_create(), is later overwritten by pppol2tp_session_init() (unless getting the tunnel's socket PMTU fails). This field is then only used when setting the PPP channel's MTU in pppol2tp_connect(). Furthermore, the SIOC[GS]IFMTU ioctls only act on the session's .mtu without propagating this value to the PPP channel, making them useless. This patch initialises the PPP channel's MTU directly and ignores the session's .mtu entirely. MTU is still computed by subtracting the PPPOL2TP_HEADER_OVERHEAD constant. It is not optimal, but that doesn't really matter: po->chan.mtu is only used when the channel is part of a multilink PPP bundle. Running multilink PPP over packet switched networks is certainly not going to be efficient, so not picking the best MTU does not harm (in the worst case, packets will just be fragmented by the underlay). The SIOC[GS]IFMTU ioctls are removed entirely (as opposed to simply ignored), because these ioctls commands are part of the requests that should be handled generically by the socket layer. PX_PROTO_OL2TP was the only socket type abusing these ioctls. Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/l2tp/l2tp_ppp.c67
1 files changed, 18 insertions, 49 deletions
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 1c6da02f976a..b403728e2757 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -553,7 +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;
- u32 mtu;
session->recv_skb = pppol2tp_recv;
#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
@@ -563,11 +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 */
- mtu = l2tp_tunnel_dst_mtu(session->tunnel);
- if (mtu)
- session->mtu = mtu - PPPOL2TP_HEADER_OVERHEAD;
}
struct l2tp_connect_info {
@@ -654,6 +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,
@@ -771,8 +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),
@@ -817,7 +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) {
@@ -873,10 +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,
@@ -1040,7 +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;
@@ -1056,39 +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;
@@ -1685,8 +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",