From: Denis Fondras <openbsd@ledeuns.net>
Subject: Re: ppp(4) : Add IPv6 support
To: Miod Vallat <miod@online.fr>
Cc: Denis Fondras <openbsd@ledeuns.net>, tech@openbsd.org
Date: Mon, 19 Feb 2024 18:16:14 +0100

Le Mon, Feb 19, 2024 at 07:01:15AM +0000, Miod Vallat a écrit :
> > Here is a diff to add IPv6 support to ppp(4).
> > With this diff, I can send and receive IPv6 packets over a PPP connection.
> 
> Look good to me, but...
> 
> > Index: if_ppp.c
> 
> > @@ -579,13 +583,9 @@ pppsioctl(struct ifnet *ifp, u_long cmd,
> >  		break;
> >  
> >  	case SIOCSIFADDR:
> > -		if (ifa->ifa_addr->sa_family != AF_INET)
> > -			error = EAFNOSUPPORT;
> >  		break;
> >  
> >  	case SIOCSIFDSTADDR:
> > -		if (ifa->ifa_addr->sa_family != AF_INET)
> > -			error = EAFNOSUPPORT;
> >  		break;
> >  
> >  	case SIOCSIFMTU:
> 
> You probably want to nevertheless check sa_family and only allow
> AF_INET, and AF_INET6 #ifdef INET6, as done e.g. in netinet/ip_carp.c.

Thank you Miod. Here is an updated diff.


Index: share/man/man4/ppp.4
===================================================================
RCS file: /cvs/src/share/man/man4/ppp.4,v
retrieving revision 1.16
diff -u -p -r1.16 ppp.4
--- share/man/man4/ppp.4	28 Jul 2015 14:31:50 -0000	1.16
+++ share/man/man4/ppp.4	19 Feb 2024 16:56:44 -0000
@@ -80,11 +80,3 @@ The
 .Nm
 device appeared in
 .Ox 1.2 .
-.Sh BUGS
-Currently, only the
-.Xr ip 4
-protocol is supported by this device.
-Note that the
-.Xr pppoe 4
-device does support
-.Xr ip6 4 .
Index: sys/net/if_ppp.c
===================================================================
RCS file: /cvs/src/sys/net/if_ppp.c,v
retrieving revision 1.117
diff -u -p -r1.117 if_ppp.c
--- sys/net/if_ppp.c	21 Aug 2020 22:59:27 -0000	1.117
+++ sys/net/if_ppp.c	19 Feb 2024 16:56:44 -0000
@@ -494,6 +494,11 @@ pppioctl(struct ppp_softc *sc, u_long cm
 		case PPP_IP:
 			npx = NP_IP;
 			break;
+#ifdef INET6
+		case PPP_IPV6:
+			npx = NP_IPV6;
+			break;
+#endif
 		default:
 			return EINVAL;
 		}
@@ -579,15 +584,19 @@ pppsioctl(struct ifnet *ifp, u_long cmd,
 		break;
 
 	case SIOCSIFADDR:
-		if (ifa->ifa_addr->sa_family != AF_INET)
-			error = EAFNOSUPPORT;
-		break;
-
 	case SIOCSIFDSTADDR:
-		if (ifa->ifa_addr->sa_family != AF_INET)
+		switch (ifa->ifa_addr->sa_family) {
+		case AF_INET:
+			break;
+#ifdef INET6
+		case AF_INET6:
+			break;
+#endif
+		default:
 			error = EAFNOSUPPORT;
+			break;
+		}
 		break;
-
 	case SIOCSIFMTU:
 		sc->sc_if.if_mtu = ifr->ifr_mtu;
 		break;
@@ -674,6 +683,14 @@ pppoutput(struct ifnet *ifp, struct mbuf
 		protocol = PPP_IP;
 		mode = sc->sc_npmode[NP_IP];
 		break;
+#ifdef INET6
+	case AF_INET6:
+		address = PPP_ALLSTATIONS;
+		control = PPP_UI;
+		protocol = PPP_IPV6;
+		mode = sc->sc_npmode[NP_IPV6];
+		break;
+#endif
 	case AF_UNSPEC:
 		address = PPP_ADDRESS(dst->sa_data);
 		control = PPP_CONTROL(dst->sa_data);
@@ -804,6 +821,11 @@ ppp_requeue(struct ppp_softc *sc)
 		case PPP_IP:
 			mode = sc->sc_npmode[NP_IP];
 			break;
+#ifdef INET6
+		case PPP_IPV6:
+			mode = sc->sc_npmode[NP_IPV6];
+			break;
+#endif
 		default:
 			mode = NPMODE_PASS;
 		}
@@ -1391,7 +1413,25 @@ ppp_inproc(struct ppp_softc *sc, struct 
 		ipv4_input(ifp, m);
 		rv = 1;
 		break;
+#ifdef INET6
+	case PPP_IPV6:
+		/*
+		 * IPv6 packet - take off the ppp header and pass it up to IPv6.
+		 */
+		if ((ifp->if_flags & IFF_UP) == 0 ||
+		    sc->sc_npmode[NP_IPV6] != NPMODE_PASS) {
+			/* interface is down - drop the packet. */
+			m_freem(m);
+			return;
+		}
+		m->m_pkthdr.len -= PPP_HDRLEN;
+		m->m_data += PPP_HDRLEN;
+		m->m_len -= PPP_HDRLEN;
 
+		ipv6_input(ifp, m);
+		rv = 1;
+		break;
+#endif
 	default:
 		/*
 		 * Some other protocol - place on input queue for read().
Index: sys/net/if_pppvar.h
===================================================================
RCS file: /cvs/src/sys/net/if_pppvar.h,v
retrieving revision 1.20
diff -u -p -r1.20 if_pppvar.h
--- sys/net/if_pppvar.h	20 May 2020 06:44:30 -0000	1.20
+++ sys/net/if_pppvar.h	19 Feb 2024 16:56:44 -0000
@@ -81,7 +81,8 @@
  * indexing sc_npmode.
  */
 #define NP_IP	0		/* Internet Protocol */
-#define NUM_NP	1		/* Number of NPs. */
+#define NP_IPV6	1		/* Internet Protocol v6 */
+#define NUM_NP	2		/* Number of NPs. */
 
 struct ppp_pkt;