[PATCH RFC net-next v2] pppoe: remove kernel-mode relay support

[Qingfang Deng <dqfext@gmail.com>]

The kernel-mode PPPoE relay feature and its two associated ioctls
(PPPOEIOCSFWD and PPPOEIOCDFWD) are not used by any existing userspace
PPPoE implementations. The most commonly-used package, RP-PPPoE [1],
handles the relaying entirely in userspace.

This legacy code has remained in the driver since its introduction in
kernel 2.3.99-pre7 for over two decades, but has served no practical
purpose.

Remove the unused relay code.

[1] https://dianne.skoll.ca/projects/rp-pppoe/

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
---
v1: restore .compat_ioctl
  https://lore.kernel.org/linux-ppp/20260211075547.138904-1-dqfext@gmail.com/

 drivers/net/ppp/pppoe.c       | 79 -----------------------------------
 drivers/net/ppp/pppox.c       |  3 --
 include/linux/if_pppox.h      |  6 ---
 include/uapi/linux/if_pppox.h | 10 -----
 4 files changed, 98 deletions(-)

diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index 4275b393a454..7a6dcfa421e9 100644
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -237,25 +237,6 @@ static inline struct pppox_sock *get_item(struct pppoe_net *pn, __be16 sid,
 	return po;
 }
 
-static inline struct pppox_sock *__get_item_by_addr(struct net *net,
-						    struct sockaddr_pppox *sp)
-{
-	struct net_device *dev;
-	struct pppoe_net *pn;
-	struct pppox_sock *pppox_sock = NULL;
-
-	int ifindex;
-
-	dev = dev_get_by_name_rcu(net, sp->sa_addr.pppoe.dev);
-	if (dev) {
-		ifindex = dev->ifindex;
-		pn = pppoe_pernet(net);
-		pppox_sock = __get_item(pn, sp->sa_addr.pppoe.sid,
-					sp->sa_addr.pppoe.remote, ifindex);
-	}
-	return pppox_sock;
-}
-
 static inline void delete_item(struct pppoe_net *pn, __be16 sid,
 					char *addr, int ifindex)
 {
@@ -369,7 +350,6 @@ static struct notifier_block pppoe_notifier = {
 static int pppoe_rcv_core(struct sock *sk, struct sk_buff *skb)
 {
 	struct pppox_sock *po = pppox_sk(sk);
-	struct pppox_sock *relay_po;
 
 	/* Backlog receive. Semantics of backlog rcv preclude any code from
 	 * executing in lock_sock()/release_sock() bounds; meaning sk->sk_state
@@ -378,17 +358,6 @@ static int pppoe_rcv_core(struct sock *sk, struct sk_buff *skb)
 
 	if (sk->sk_state & PPPOX_BOUND) {
 		ppp_input(&po->chan, skb);
-	} else if (sk->sk_state & PPPOX_RELAY) {
-		relay_po = __get_item_by_addr(sock_net(sk),
-					      &po->pppoe_relay);
-		if (relay_po == NULL)
-			goto abort_kfree;
-
-		if ((sk_pppox(relay_po)->sk_state & PPPOX_CONNECTED) == 0)
-			goto abort_kfree;
-
-		if (!__pppoe_xmit(sk_pppox(relay_po), skb))
-			goto abort_kfree;
 	} else {
 		if (sock_queue_rcv_skb(sk, skb))
 			goto abort_kfree;
@@ -656,7 +625,6 @@ static int pppoe_connect(struct socket *sock, struct sockaddr_unsized *uservaddr
 
 		po->pppoe_ifindex = 0;
 		memset(&po->pppoe_pa, 0, sizeof(po->pppoe_pa));
-		memset(&po->pppoe_relay, 0, sizeof(po->pppoe_relay));
 		memset(&po->chan, 0, sizeof(po->chan));
 		po->next = NULL;
 		po->num = 0;
@@ -783,53 +751,6 @@ static int pppoe_ioctl(struct socket *sock, unsigned int cmd,
 		err = 0;
 		break;
 
-	case PPPOEIOCSFWD:
-	{
-		struct pppox_sock *relay_po;
-
-		err = -EBUSY;
-		if (sk->sk_state & (PPPOX_BOUND | PPPOX_DEAD))
-			break;
-
-		err = -ENOTCONN;
-		if (!(sk->sk_state & PPPOX_CONNECTED))
-			break;
-
-		/* PPPoE address from the user specifies an outbound
-		   PPPoE address which frames are forwarded to */
-		err = -EFAULT;
-		if (copy_from_user(&po->pppoe_relay,
-				   (void __user *)arg,
-				   sizeof(struct sockaddr_pppox)))
-			break;
-
-		err = -EINVAL;
-		if (po->pppoe_relay.sa_family != AF_PPPOX ||
-		    po->pppoe_relay.sa_protocol != PX_PROTO_OE)
-			break;
-
-		/* Check that the socket referenced by the address
-		   actually exists. */
-		rcu_read_lock();
-		relay_po = __get_item_by_addr(sock_net(sk), &po->pppoe_relay);
-		rcu_read_unlock();
-		if (!relay_po)
-			break;
-
-		sk->sk_state |= PPPOX_RELAY;
-		err = 0;
-		break;
-	}
-
-	case PPPOEIOCDFWD:
-		err = -EALREADY;
-		if (!(sk->sk_state & PPPOX_RELAY))
-			break;
-
-		sk->sk_state &= ~PPPOX_RELAY;
-		err = 0;
-		break;
-
 	default:
 		err = -ENOTTY;
 	}
diff --git a/drivers/net/ppp/pppox.c b/drivers/net/ppp/pppox.c
index 08364f10a43f..5861a2f6ce3e 100644
--- a/drivers/net/ppp/pppox.c
+++ b/drivers/net/ppp/pppox.c
@@ -102,9 +102,6 @@ EXPORT_SYMBOL(pppox_ioctl);
 #ifdef CONFIG_COMPAT
 int pppox_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 {
-	if (cmd == PPPOEIOCSFWD32)
-		cmd = PPPOEIOCSFWD;
-
 	return pppox_ioctl(sock, cmd, (unsigned long)compat_ptr(arg));
 }
 
diff --git a/include/linux/if_pppox.h b/include/linux/if_pppox.h
index db45d6f1c4f4..8bbf676c2a85 100644
--- a/include/linux/if_pppox.h
+++ b/include/linux/if_pppox.h
@@ -25,8 +25,6 @@ struct pppoe_opt {
 	struct net_device      *dev;	  /* device associated with socket*/
 	int			ifindex;  /* ifindex of device associated with socket */
 	struct pppoe_addr	pa;	  /* what this socket is bound to*/
-	struct sockaddr_pppox	relay;	  /* what socket data will be
-					     relayed to (PPPoE relaying) */
 	struct work_struct      padt_work;/* Work item for handling PADT */
 };
 
@@ -53,7 +51,6 @@ struct pppox_sock {
 #define pppoe_dev	proto.pppoe.dev
 #define pppoe_ifindex	proto.pppoe.ifindex
 #define pppoe_pa	proto.pppoe.pa
-#define pppoe_relay	proto.pppoe.relay
 
 static inline struct pppox_sock *pppox_sk(struct sock *sk)
 {
@@ -80,14 +77,11 @@ extern void pppox_unbind_sock(struct sock *sk);/* delete ppp-channel binding */
 extern int pppox_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
 extern int pppox_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
 
-#define PPPOEIOCSFWD32    _IOW(0xB1 ,0, compat_size_t)
-
 /* PPPoX socket states */
 enum {
     PPPOX_NONE		= 0,  /* initial state */
     PPPOX_CONNECTED	= 1,  /* connection established ==TCP_ESTABLISHED */
     PPPOX_BOUND		= 2,  /* bound to ppp device */
-    PPPOX_RELAY		= 4,  /* forwarding is enabled */
     PPPOX_DEAD		= 16  /* dead, useless, please clean me up!*/
 };
 
diff --git a/include/uapi/linux/if_pppox.h b/include/uapi/linux/if_pppox.h
index 9abd80dcc46f..8fdf0a681a4e 100644
--- a/include/uapi/linux/if_pppox.h
+++ b/include/uapi/linux/if_pppox.h
@@ -103,16 +103,6 @@ struct sockaddr_pppol2tpv3in6 {
 	struct pppol2tpv3in6_addr pppol2tp;
 } __packed;
 
-/*********************************************************************
- *
- * ioctl interface for defining forwarding of connections
- *
- ********************************************************************/
-
-#define PPPOEIOCSFWD	_IOW(0xB1 ,0, size_t)
-#define PPPOEIOCDFWD	_IO(0xB1 ,1)
-/*#define PPPOEIOCGFWD	_IOWR(0xB1,2, size_t)*/
-
 /* Codes to identify message types */
 #define PADI_CODE	0x09
 #define PADO_CODE	0x07
-- 
2.43.0