diff --git a/src/include/netif/ppp/ppp.h b/src/include/netif/ppp/ppp.h
index 6d24770f..ec5eaf4f 100644
--- a/src/include/netif/ppp/ppp.h
+++ b/src/include/netif/ppp/ppp.h
@@ -303,19 +303,13 @@ struct ppp_addrs {
 /*
  * PPP interface control block.
  */
-typedef int (*link_command_cb_fn)(void *pcb, u8_t command);
-typedef int (*link_write_cb_fn)(void *pcb, struct pbuf *p);
-typedef err_t (*link_netif_output_cb_fn)(void *pcb, struct pbuf *p, u_short protocol);
-
 struct ppp_pcb_s {
   /* -- below are data that will NOT be cleared between two sessions */
 #if PPP_DEBUG
   u8_t num;                      /* Interface number - only useful for debugging */
 #endif /* PPP_DEBUG */
   ppp_settings settings;
-  link_command_cb_fn link_command_cb;
-  link_write_cb_fn link_write_cb;
-  link_netif_output_cb_fn link_netif_output_cb;
+  const struct link_callbacks *link_cb;
   void *link_ctx_cb;
   void (*link_status_cb)(ppp_pcb *pcb, int err_code, void *ctx);  /* Status change callback */
 #if PPP_NOTIFY_PHASE
diff --git a/src/include/netif/ppp/ppp_impl.h b/src/include/netif/ppp/ppp_impl.h
index 33e2f3d3..fb5f0393 100644
--- a/src/include/netif/ppp/ppp_impl.h
+++ b/src/include/netif/ppp/ppp_impl.h
@@ -93,16 +93,6 @@
  */
 #define PPP_LINK_ENABLED_NUMBER (!!PPPOS_SUPPORT+!!PPPOE_SUPPORT+!!PPPOL2TP_SUPPORT)
 
-/*
- * Low-level links commands
- */
-/* Start a connection (i.e. initiate discovery phase) */
-#define PPP_LINK_COMMAND_CONNECT      0
-/* End a connection (i.e. initiate disconnect phase) */
-#define PPP_LINK_COMMAND_DISCONNECT   1
-/* Free link connection */
-#define PPP_LINK_COMMAND_FREE         2
-
 /*
  * Protocol field values.
  */
@@ -152,6 +142,23 @@
 #define PPP_EAP		0xc227	/* Extensible Authentication Protocol */
 #endif /* EAP_SUPPORT */
 
+/*
+ * The following struct gives the addresses of procedures to call
+ * for a particular lower link level protocol.
+ */
+struct link_callbacks {
+  /* Start a connection (e.g. Initiate discovery phase) */
+  err_t (*connect) (ppp_pcb *pcb, void *ctx);
+  /* End a connection (i.e. initiate disconnect phase) */
+  void (*disconnect) (ppp_pcb *pcb, void *ctx);
+  /* Free lower protocol control block */
+  err_t (*free) (ppp_pcb *pcb, void *ctx);
+  /* Write a pbuf to a ppp link, only used from PPP functions to send PPP packets. */
+  err_t (*write)(ppp_pcb *pcb, void *ctx, struct pbuf *p);
+  /* Send a packet from lwIP core (IPv4 or IPv6) */
+  err_t (*netif_output)(ppp_pcb *pcb, void *ctx, struct pbuf *p, u_short protocol);
+};
+
 /*
  * What to do with network protocol (NP) packets.
  */
@@ -380,8 +387,8 @@ ppp_pcb *ppp_new(struct netif *pppif, ppp_link_status_cb_fn link_status_cb, void
 /* Set a PPP PCB to its initial state */
 void ppp_clear(ppp_pcb *pcb);
 
-/* Set link callback function */
-void ppp_link_set_callbacks(ppp_pcb *pcb, link_command_cb_fn command, link_write_cb_fn write, link_netif_output_cb_fn netif_output, void *ctx);
+/* Set link callback functions */
+void ppp_link_set_callbacks(ppp_pcb *pcb, const struct link_callbacks *callbacks, void *ctx);
 
 /* Initiate LCP open request */
 void ppp_start(ppp_pcb *pcb);
diff --git a/src/netif/ppp/ppp.c b/src/netif/ppp/ppp.c
index 587a8dd2..76cab5d7 100644
--- a/src/netif/ppp/ppp.c
+++ b/src/netif/ppp/ppp.c
@@ -258,7 +258,7 @@ int ppp_open(ppp_pcb *pcb, u16_t holdoff) {
   PPPDEBUG(LOG_DEBUG, ("ppp_open() called, holdoff=%d\n", holdoff));
 
   if (holdoff == 0) {
-    return pcb->link_command_cb(pcb->link_ctx_cb, PPP_LINK_COMMAND_CONNECT);
+    return pcb->link_cb->connect(pcb, pcb->link_ctx_cb);
   }
 
   new_phase(pcb, PPP_PHASE_HOLDOFF);
@@ -329,7 +329,7 @@ int ppp_free(ppp_pcb *pcb) {
 
   netif_remove(pcb->netif);
 
-  err = pcb->link_command_cb(pcb->link_ctx_cb, PPP_LINK_COMMAND_FREE);
+  err = pcb->link_cb->free(pcb, pcb->link_ctx_cb);
 
   memp_free(MEMP_PPP_PCB, pcb);
   return err;
@@ -425,7 +425,7 @@ static void ppp_do_open(void *arg) {
 
   LWIP_ASSERT("pcb->phase == PPP_PHASE_DEAD || pcb->phase == PPP_PHASE_HOLDOFF", pcb->phase == PPP_PHASE_DEAD || pcb->phase == PPP_PHASE_HOLDOFF);
 
-  pcb->link_command_cb(pcb->link_ctx_cb, PPP_LINK_COMMAND_CONNECT);
+  pcb->link_cb->connect(pcb, pcb->link_ctx_cb);
 }
 
 /*
@@ -491,7 +491,7 @@ static err_t ppp_netif_output(struct netif *netif, struct pbuf *pb, u_short prot
     return ERR_RTE;
   }
 
-  return pcb->link_netif_output_cb(pcb->link_ctx_cb, pb, protocol);
+  return pcb->link_cb->netif_output(pcb, pcb->link_ctx_cb, pb, protocol);
 }
 
 
@@ -614,10 +614,8 @@ void ppp_clear(ppp_pcb *pcb) {
   new_phase(pcb, PPP_PHASE_INITIALIZE);
 }
 
-void ppp_link_set_callbacks(ppp_pcb *pcb, link_command_cb_fn command, link_write_cb_fn write, link_netif_output_cb_fn netif_output, void *ctx) {
-  pcb->link_command_cb = command;
-  pcb->link_write_cb = write;
-  pcb->link_netif_output_cb = netif_output;
+void ppp_link_set_callbacks(ppp_pcb *pcb, const struct link_callbacks *callbacks, void *ctx) {
+  pcb->link_cb = callbacks;
   pcb->link_ctx_cb = ctx;
 }
 
@@ -809,7 +807,7 @@ int ppp_write(ppp_pcb *pcb, struct pbuf *p) {
 #if PRINTPKT_SUPPORT
   ppp_dump_packet("sent", (unsigned char *)p->payload+2, p->len-2);
 #endif /* PRINTPKT_SUPPORT */
-  return pcb->link_write_cb(pcb->link_ctx_cb, p);
+  return pcb->link_cb->write(pcb, pcb->link_ctx_cb, p);
 }
 
 /* merge a pbuf chain into one pbuf */
@@ -840,7 +838,7 @@ struct pbuf * ppp_singlebuf(struct pbuf *p) {
 
 void ppp_link_terminated(ppp_pcb *pcb) {
   PPPDEBUG(LOG_DEBUG, ("ppp_link_terminated: unit %d\n", pcb->num));
-  pcb->link_command_cb(pcb->link_ctx_cb, PPP_LINK_COMMAND_DISCONNECT);
+  pcb->link_cb->disconnect(pcb, pcb->link_ctx_cb);
   PPPDEBUG(LOG_DEBUG, ("ppp_link_terminated: finished.\n"));
 }
 
diff --git a/src/netif/ppp/pppoe.c b/src/netif/ppp/pppoe.c
index 77a6d69a..0caa005a 100644
--- a/src/netif/ppp/pppoe.c
+++ b/src/netif/ppp/pppoe.c
@@ -117,14 +117,13 @@ static char pppoe_error_tmp[PPPOE_ERRORSTRING_LEN];
 
 
 /* callbacks called from PPP core */
-static int pppoe_link_command_callback(void *pcb, u8_t command);
-static int pppoe_link_write_callback(void *pcb, struct pbuf *p);
-static err_t pppoe_link_netif_output_callback(void *pcb, struct pbuf *p, u_short protocol);
+static err_t pppoe_link_write_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p);
+static err_t pppoe_link_netif_output_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p, u_short protocol);
+static err_t pppoe_connect(ppp_pcb *ppp, void *ctx);
+static void pppoe_disconnect(ppp_pcb *ppp, void *ctx);
+static err_t pppoe_destroy(ppp_pcb *ppp, void *ctx);
 
 /* management routines */
-static err_t pppoe_destroy(struct pppoe_softc *sc);
-static int pppoe_connect(struct pppoe_softc *sc);
-static void pppoe_disconnect(struct pppoe_softc *sc);
 static void pppoe_abort_connect(struct pppoe_softc *);
 static void pppoe_clear_softc(struct pppoe_softc *, const char *);
 
@@ -148,6 +147,15 @@ static struct pppoe_softc* pppoe_find_softc_by_hunique(u8_t *token, size_t len,
 /** linked list of created pppoe interfaces */
 static struct pppoe_softc *pppoe_softc_list;
 
+/* Callbacks structure for PPP core */
+static const struct link_callbacks pppoe_callbacks = {
+  pppoe_connect,
+  pppoe_disconnect,
+  pppoe_destroy,
+  pppoe_link_write_callback,
+  pppoe_link_netif_output_callback
+};
+
 /*
  * Create a new PPP Over Ethernet (PPPoE) connection.
  *
@@ -185,35 +193,13 @@ ppp_pcb *pppoe_create(struct netif *pppif,
   sc->next = pppoe_softc_list;
   pppoe_softc_list = sc;
 
-  ppp_link_set_callbacks(ppp, pppoe_link_command_callback, pppoe_link_write_callback, pppoe_link_netif_output_callback, sc);
+  ppp_link_set_callbacks(ppp, &pppoe_callbacks, sc);
   return ppp;
 }
 
 /* Called by PPP core */
-static int pppoe_link_command_callback(void *pcb, u8_t command) {
-  struct pppoe_softc *sc = (struct pppoe_softc *)pcb;
-
-  switch(command) {
-  case PPP_LINK_COMMAND_CONNECT:
-    return pppoe_connect(sc);
-
-  case PPP_LINK_COMMAND_DISCONNECT:
-    pppoe_disconnect(sc);
-    break;
-
-  case PPP_LINK_COMMAND_FREE:
-    return pppoe_destroy(sc);
-
-  default: ;
-  }
-
-  return PPPERR_NONE;
-}
-
-/* Called by PPP core */
-static int pppoe_link_write_callback(void *pcb, struct pbuf *p) {
-  struct pppoe_softc *sc = (struct pppoe_softc *)pcb;
-  ppp_pcb *ppp = sc->pcb;
+static err_t pppoe_link_write_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p) {
+  struct pppoe_softc *sc = (struct pppoe_softc *)ctx;
   struct pbuf *ph; /* Ethernet + PPPoE header */
 #if LWIP_SNMP
   u16_t tot_len;
@@ -252,9 +238,8 @@ static int pppoe_link_write_callback(void *pcb, struct pbuf *p) {
 }
 
 /* Called by PPP core */
-static err_t pppoe_link_netif_output_callback(void *pcb, struct pbuf *p, u_short protocol) {
-  struct pppoe_softc *sc = (struct pppoe_softc *)pcb;
-  ppp_pcb *ppp = sc->pcb;
+static err_t pppoe_link_netif_output_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p, u_short protocol) {
+  struct pppoe_softc *sc = (struct pppoe_softc *)ctx;
   struct pbuf *pb;
   int i=0;
 #if LWIP_SNMP
@@ -298,9 +283,11 @@ static err_t pppoe_link_netif_output_callback(void *pcb, struct pbuf *p, u_short
 }
 
 static err_t
-pppoe_destroy(struct pppoe_softc *sc)
+pppoe_destroy(ppp_pcb *ppp, void *ctx)
 {
+  struct pppoe_softc *sc = (struct pppoe_softc *)ctx;
   struct pppoe_softc **copp, *freep;
+  LWIP_UNUSED_ARG(ppp);
 
   sys_untimeout(pppoe_timeout, sc);
 
@@ -906,11 +893,11 @@ pppoe_timeout(void *arg)
 }
 
 /* Start a connection (i.e. initiate discovery phase) */
-static int
-pppoe_connect(struct pppoe_softc *sc)
+static err_t
+pppoe_connect(ppp_pcb *ppp, void *ctx)
 {
   int err;
-  ppp_pcb *ppp = sc->pcb;
+  struct pppoe_softc *sc = (struct pppoe_softc *)ctx;
   lcp_options *lcp_wo;
   lcp_options *lcp_ao;
   ipcp_options *ipcp_wo;
@@ -965,8 +952,10 @@ pppoe_connect(struct pppoe_softc *sc)
 
 /* disconnect */
 static void
-pppoe_disconnect(struct pppoe_softc *sc)
+pppoe_disconnect(ppp_pcb *ppp, void *ctx)
 {
+  struct pppoe_softc *sc = (struct pppoe_softc *)ctx;
+
   if (sc->sc_state < PPPOE_STATE_SESSION) {
     return;
   }
@@ -989,7 +978,7 @@ pppoe_disconnect(struct pppoe_softc *sc)
   sc->sc_padi_retried = 0;
   sc->sc_padr_retried = 0;
 
-  ppp_link_end(sc->pcb); /* notify upper layers */
+  ppp_link_end(ppp); /* notify upper layers */
   return;
 }
 
diff --git a/src/netif/ppp/pppol2tp.c b/src/netif/ppp/pppol2tp.c
index 08dd0e12..7c920ad2 100644
--- a/src/netif/ppp/pppol2tp.c
+++ b/src/netif/ppp/pppol2tp.c
@@ -75,14 +75,13 @@
 #endif /* PPPOL2TP_AUTH_SUPPORT */
 
 /* callbacks called from PPP core */
-static int pppol2tp_link_command_callback(void *pcb, u8_t command);
-static int pppol2tp_link_write_callback(void *pcb, struct pbuf *p);
-static err_t pppol2tp_link_netif_output_callback(void *pcb, struct pbuf *p, u_short protocol);
+static err_t pppol2tp_link_write_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p);
+static err_t pppol2tp_link_netif_output_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p, u_short protocol);
+static err_t pppol2tp_destroy(ppp_pcb *ppp, void *ctx);    /* Destroy a L2TP control block */
+static err_t pppol2tp_connect(ppp_pcb *ppp, void *ctx);    /* Be a LAC, connect to a LNS. */
+static void pppol2tp_disconnect(ppp_pcb *ppp, void *ctx);  /* Disconnect */
 
  /* Prototypes for procedures local to this file. */
-static err_t pppol2tp_destroy(pppol2tp_pcb *l2tp);    /* Destroy a L2TP control block */
-static err_t pppol2tp_connect(pppol2tp_pcb *l2tp);    /* Be a LAC, connect to a LNS. */
-static void pppol2tp_disconnect(pppol2tp_pcb *l2tp);  /* Disconnect */
 static void pppol2tp_input(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port);
 static void pppol2tp_dispatch_control_packet(pppol2tp_pcb *l2tp, struct ip_addr *addr, u16_t port,
              struct pbuf *p, u16_t len, u16_t tunnel_id, u16_t session_id, u16_t ns, u16_t nr);
@@ -97,6 +96,15 @@ static err_t pppol2tp_send_zlb(pppol2tp_pcb *l2tp, u16_t ns);
 static err_t pppol2tp_send_stopccn(pppol2tp_pcb *l2tp, u16_t ns);
 static err_t pppol2tp_xmit(pppol2tp_pcb *l2tp, struct pbuf *pb);
 
+/* Callbacks structure for PPP core */
+static const struct link_callbacks pppol2tp_callbacks = {
+  pppol2tp_connect,
+  pppol2tp_disconnect,
+  pppol2tp_destroy,
+  pppol2tp_link_write_callback,
+  pppol2tp_link_netif_output_callback
+};
+
 
 /* Create a new L2TP session. */
 ppp_pcb *pppol2tp_create(struct netif *pppif,
@@ -138,35 +146,13 @@ ppp_pcb *pppol2tp_create(struct netif *pppif,
   l2tp->secret_len = secret_len;
 #endif /* PPPOL2TP_AUTH_SUPPORT */
 
-  ppp_link_set_callbacks(ppp, pppol2tp_link_command_callback, pppol2tp_link_write_callback, pppol2tp_link_netif_output_callback, l2tp);
+  ppp_link_set_callbacks(ppp, &pppol2tp_callbacks, l2tp);
   return ppp;
 }
 
 /* Called by PPP core */
-static int pppol2tp_link_command_callback(void *pcb, u8_t command) {
-  pppol2tp_pcb *l2tp = (pppol2tp_pcb *)pcb;
-
-  switch(command) {
-  case PPP_LINK_COMMAND_CONNECT:
-    return pppol2tp_connect(l2tp);
-
-  case PPP_LINK_COMMAND_DISCONNECT:
-    pppol2tp_disconnect(l2tp);
-    break;
-
-  case PPP_LINK_COMMAND_FREE:
-    return pppol2tp_destroy(l2tp);
-
-  default: ;
-  }
-
-  return PPPERR_NONE;
-}
-
-/* Called by PPP core */
-static int pppol2tp_link_write_callback(void *pcb, struct pbuf *p) {
-  pppol2tp_pcb *l2tp = (pppol2tp_pcb *)pcb;
-  ppp_pcb *ppp = l2tp->ppp;
+static err_t pppol2tp_link_write_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p) {
+  pppol2tp_pcb *l2tp = (pppol2tp_pcb *)ctx;
   struct pbuf *ph; /* UDP + L2TP header */
 #if LWIP_SNMP
   u16_t tot_len;
@@ -202,9 +188,8 @@ static int pppol2tp_link_write_callback(void *pcb, struct pbuf *p) {
 }
 
 /* Called by PPP core */
-static err_t pppol2tp_link_netif_output_callback(void *pcb, struct pbuf *p, u_short protocol) {
-  pppol2tp_pcb *l2tp = (pppol2tp_pcb *)pcb;
-  ppp_pcb *ppp = l2tp->ppp;
+static err_t pppol2tp_link_netif_output_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p, u_short protocol) {
+  pppol2tp_pcb *l2tp = (pppol2tp_pcb *)ctx;
   struct pbuf *pb;
   int i=0;
 #if LWIP_SNMP
@@ -248,7 +233,9 @@ static err_t pppol2tp_link_netif_output_callback(void *pcb, struct pbuf *p, u_sh
 }
 
 /* Destroy a L2TP control block */
-static err_t pppol2tp_destroy(pppol2tp_pcb *l2tp) {
+static err_t pppol2tp_destroy(ppp_pcb *ppp, void *ctx) {
+  pppol2tp_pcb *l2tp = (pppol2tp_pcb *)ctx;
+  LWIP_UNUSED_ARG(ppp);
 
   sys_untimeout(pppol2tp_timeout, l2tp);
   if (l2tp->udp != NULL) {
@@ -259,9 +246,9 @@ static err_t pppol2tp_destroy(pppol2tp_pcb *l2tp) {
 }
 
 /* Be a LAC, connect to a LNS. */
-static err_t pppol2tp_connect(pppol2tp_pcb *l2tp) {
+static err_t pppol2tp_connect(ppp_pcb *ppp, void *ctx) {
   err_t err;
-  ppp_pcb *ppp = l2tp->ppp;
+  pppol2tp_pcb *l2tp = (pppol2tp_pcb *)ctx;
   lcp_options *lcp_wo;
   lcp_options *lcp_ao;
   ipcp_options *ipcp_wo;
@@ -321,7 +308,8 @@ static err_t pppol2tp_connect(pppol2tp_pcb *l2tp) {
 }
 
 /* Disconnect */
-static void pppol2tp_disconnect(pppol2tp_pcb *l2tp) {
+static void pppol2tp_disconnect(ppp_pcb *ppp, void *ctx) {
+  pppol2tp_pcb *l2tp = (pppol2tp_pcb *)ctx;
 
   if (l2tp->phase < PPPOL2TP_STATE_DATA) {
     return;
@@ -331,7 +319,7 @@ static void pppol2tp_disconnect(pppol2tp_pcb *l2tp) {
   pppol2tp_send_stopccn(l2tp, l2tp->our_ns);
 
   pppol2tp_clear(l2tp);
-  ppp_link_end(l2tp->ppp); /* notify upper layers */
+  ppp_link_end(ppp); /* notify upper layers */
 }
 
 /* UDP Callback for incoming L2TP frames */
diff --git a/src/netif/ppp/pppos.c b/src/netif/ppp/pppos.c
index 0640679d..4709766e 100644
--- a/src/netif/ppp/pppos.c
+++ b/src/netif/ppp/pppos.c
@@ -82,14 +82,13 @@ static u8_t pppos_exist(pppos_pcb *pppos);
 #endif /* PPPOS_PCB_LIST */
 
 /* callbacks called from PPP core */
-static int pppos_link_command_callback(void *pcb, u8_t command);
-static int pppos_link_write_callback(void *pcb, struct pbuf *p);
-static err_t pppos_link_netif_output_callback(void *pcb, struct pbuf *pb, u_short protocol);
+static err_t pppos_link_write_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p);
+static err_t pppos_link_netif_output_callback(ppp_pcb *ppp, void *ctx, struct pbuf *pb, u_short protocol);
+static err_t pppos_connect(ppp_pcb *ppp, void *ctx);
+static void pppos_disconnect(ppp_pcb *ppp, void *ctx);
+static err_t pppos_destroy(ppp_pcb *ppp, void *ctx);
 
 /* Prototypes for procedures local to this file. */
-static void pppos_connect(pppos_pcb *pppos);
-static void pppos_disconnect(pppos_pcb *pppos);
-static err_t pppos_destroy(pppos_pcb *pppos);
 #if PPP_INPROC_MULTITHREADED
 static void pppos_input_callback(void *arg);
 #endif /* PPP_INPROC_MULTITHREADED */
@@ -98,6 +97,15 @@ static void pppos_free_current_input_packet(pppos_pcb *pppos);
 static struct pbuf *pppos_append(u_char c, struct pbuf *nb, ext_accm *out_accm);
 static void pppos_drop(pppos_pcb *pppos);
 
+/* Callbacks structure for PPP core */
+static const struct link_callbacks pppos_callbacks = {
+  pppos_connect,
+  pppos_disconnect,
+  pppos_destroy,
+  pppos_link_write_callback,
+  pppos_link_netif_output_callback
+};
+
 /* PPP's Asynchronous-Control-Character-Map.  The mask array is used
  * to select the specific bit for a character. */
 static const u_char ppp_accm_mask[] = { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80 };
@@ -200,40 +208,15 @@ ppp_pcb *pppos_create(struct netif *pppif, sio_fd_t fd,
 
   pppos->ppp = ppp;
   pppos->fd = fd;
-  ppp_link_set_callbacks(ppp, pppos_link_command_callback, pppos_link_write_callback, pppos_link_netif_output_callback, pppos);
+  ppp_link_set_callbacks(ppp, &pppos_callbacks, pppos);
   return ppp;
 }
 
 /* Called by PPP core */
-static int
-pppos_link_command_callback(void *pcb, u8_t command)
+static err_t
+pppos_link_write_callback(ppp_pcb *ppp, void *ctx, struct pbuf *p)
 {
-  pppos_pcb *pppos = (pppos_pcb *)pcb;
-
-  switch(command) {
-  case PPP_LINK_COMMAND_CONNECT:
-    pppos_connect(pppos);
-    break;
-
-  case PPP_LINK_COMMAND_DISCONNECT:
-    pppos_disconnect(pppos);
-    break;
-
-  case PPP_LINK_COMMAND_FREE:
-    return pppos_destroy(pppos);
-
-  default: ;
-  }
-
-  return PPPERR_NONE;
-}
-
-/* Called by PPP core */
-static int
-pppos_link_write_callback(void *pcb, struct pbuf *p)
-{
-  pppos_pcb *pppos = (pppos_pcb *)pcb;
-  ppp_pcb *ppp = pppos->ppp;
+  pppos_pcb *pppos = (pppos_pcb *)ctx;
   u_char *s = (u_char*)p->payload;
   int n = p->len;
   u_char c;
@@ -300,10 +283,9 @@ pppos_link_write_callback(void *pcb, struct pbuf *p)
 
 /* Called by PPP core */
 static err_t
-pppos_link_netif_output_callback(void *pcb, struct pbuf *pb, u_short protocol)
+pppos_link_netif_output_callback(ppp_pcb *ppp, void *ctx, struct pbuf *pb, u_short protocol)
 {
-  pppos_pcb *pppos = (pppos_pcb *)pcb;
-  ppp_pcb *ppp = pppos->ppp;
+  pppos_pcb *pppos = (pppos_pcb *)ctx;
   u_int fcs_out = PPP_INITFCS;
   struct pbuf *head = NULL, *tail = NULL, *p;
   u_char c;
@@ -427,10 +409,10 @@ pppos_exist(pppos_pcb *pppos)
 }
 #endif /* PPPOS_PCB_LIST */
 
-static void
-pppos_connect(pppos_pcb *pppos)
+static err_t
+pppos_connect(ppp_pcb *ppp, void *ctx)
 {
-  ppp_pcb *ppp = pppos->ppp;
+  pppos_pcb *pppos = (pppos_pcb *)ctx;
 #if !VJ_SUPPORT
   ipcp_options *ipcp_wo;
   ipcp_options *ipcp_ao;
@@ -468,12 +450,13 @@ pppos_connect(pppos_pcb *pppos)
    */
   PPPDEBUG(LOG_INFO, ("pppos_connect: unit %d: connecting\n", ppp->num));
   ppp_start(ppp); /* notify upper layers */
+  return ERR_OK;
 }
 
 static void
-pppos_disconnect(pppos_pcb *pppos)
+pppos_disconnect(ppp_pcb *ppp, void *ctx)
 {
-  ppp_pcb *ppp = pppos->ppp;
+  LWIP_UNUSED_ARG(ctx);
 
   /* We cannot call ppp_free_current_input_packet() here because
    * rx thread might still call pppos_input()
@@ -482,11 +465,15 @@ pppos_disconnect(pppos_pcb *pppos)
 }
 
 static err_t
-pppos_destroy(pppos_pcb *pppos)
+pppos_destroy(ppp_pcb *ppp, void *ctx)
 {
+  pppos_pcb *pppos = (pppos_pcb *)ctx;
 #if PPPOS_PCB_LIST
   pppos_pcb **copp, *freep;
+#endif /* PPPOS_PCB_LIST */
+  LWIP_UNUSED_ARG(ppp);
 
+#if PPPOS_PCB_LIST
   /* remove interface from list */
   for (copp = &pppos_pcb_list; (freep = *copp); copp = &freep->next) {
     if (freep == pppos) {