diff --git a/src/include/netif/ppp/ccp.h b/src/include/netif/ppp/ccp.h
index b5dee384..f106cb5d 100644
--- a/src/include/netif/ppp/ccp.h
+++ b/src/include/netif/ppp/ccp.h
@@ -52,6 +52,6 @@ extern ccp_options ccp_gotoptions[];
 extern ccp_options ccp_allowoptions[];
 extern ccp_options ccp_hisoptions[];
 
-extern struct protent ccp_protent;
+extern const struct protent ccp_protent;
 
 #endif /* PPP_SUPPORT && CCP_SUPPORT */
diff --git a/src/include/netif/ppp/chap-new.h b/src/include/netif/ppp/chap-new.h
index 2730a8cb..d84e9029 100644
--- a/src/include/netif/ppp/chap-new.h
+++ b/src/include/netif/ppp/chap-new.h
@@ -192,7 +192,7 @@ extern void chap_auth_peer(ppp_pcb *pcb, char *our_name, int digest_code);
 extern void chap_auth_with_peer(ppp_pcb *pcb, char *our_name, int digest_code);
 
 /* Represents the CHAP protocol to the main pppd code */
-extern struct protent chap_protent;
+extern const struct protent chap_protent;
 
 #endif /* CHAP_H */
 #endif /* PPP_SUPPORT && CHAP_SUPPORT */
diff --git a/src/include/netif/ppp/eap.h b/src/include/netif/ppp/eap.h
index b96be43c..328046c1 100644
--- a/src/include/netif/ppp/eap.h
+++ b/src/include/netif/ppp/eap.h
@@ -157,7 +157,7 @@ typedef struct eap_state {
 void eap_authwithpeer(ppp_pcb *pcb, char *localname);
 void eap_authpeer(ppp_pcb *pcb, char *localname);
 
-extern struct protent eap_protent;
+extern const struct protent eap_protent;
 
 #ifdef	__cplusplus
 }
diff --git a/src/include/netif/ppp/ecp.h b/src/include/netif/ppp/ecp.h
index d6887758..cba6678e 100644
--- a/src/include/netif/ppp/ecp.h
+++ b/src/include/netif/ppp/ecp.h
@@ -45,6 +45,6 @@ extern ecp_options ecp_gotoptions[];
 extern ecp_options ecp_allowoptions[];
 extern ecp_options ecp_hisoptions[];
 
-extern struct protent ecp_protent;
+extern const struct protent ecp_protent;
 
 #endif /* PPP_SUPPORT && ECP_SUPPORT */
diff --git a/src/include/netif/ppp/ipcp.h b/src/include/netif/ppp/ipcp.h
index 5b6f1006..b5f2334c 100644
--- a/src/include/netif/ppp/ipcp.h
+++ b/src/include/netif/ppp/ipcp.h
@@ -101,7 +101,7 @@ typedef struct ipcp_options {
 char *ip_ntoa (u32_t);
 #endif /* UNUSED, already defined by lwIP */
 
-extern struct protent ipcp_protent;
+extern const struct protent ipcp_protent;
 
 #endif /* IPCP_H */
 #endif /* PPP_SUPPORT */
diff --git a/src/include/netif/ppp/ipv6cp.h b/src/include/netif/ppp/ipv6cp.h
index 8501d9c0..d6e28a8d 100644
--- a/src/include/netif/ppp/ipv6cp.h
+++ b/src/include/netif/ppp/ipv6cp.h
@@ -173,7 +173,7 @@ typedef struct ipv6cp_options {
     eui64_t ourid, hisid;       /* Interface identifiers */
 } ipv6cp_options;
 
-extern struct protent ipv6cp_protent;
+extern const struct protent ipv6cp_protent;
 
 #endif /* IPV6CP_H */
 #endif /* PPP_SUPPORT && PPP_IPV6_SUPPORT */
diff --git a/src/include/netif/ppp/lcp.h b/src/include/netif/ppp/lcp.h
index 00a0f576..f832a4ee 100644
--- a/src/include/netif/ppp/lcp.h
+++ b/src/include/netif/ppp/lcp.h
@@ -164,7 +164,7 @@ void lcp_lowerup(ppp_pcb *pcb);
 void lcp_lowerdown(ppp_pcb *pcb);
 void lcp_sprotrej(ppp_pcb *pcb, u_char *p, int len);    /* send protocol reject */
 
-extern struct protent lcp_protent;
+extern const struct protent lcp_protent;
 
 /* Default number of times we receive our magic number from the peer
    before deciding the link is looped-back. */
diff --git a/src/include/netif/ppp/ppp_impl.h b/src/include/netif/ppp/ppp_impl.h
index 61ed84c1..06d40b6b 100644
--- a/src/include/netif/ppp/ppp_impl.h
+++ b/src/include/netif/ppp/ppp_impl.h
@@ -295,7 +295,7 @@ struct protent {
 };
 
 /* Table of pointers to supported protocols */
-extern struct protent *protocols[];
+extern const struct protent* const protocols[];
 
 
 /* Values for auth_pending, auth_done */
diff --git a/src/include/netif/ppp/upap.h b/src/include/netif/ppp/upap.h
index ca051411..3d1075b2 100644
--- a/src/include/netif/ppp/upap.h
+++ b/src/include/netif/ppp/upap.h
@@ -120,7 +120,7 @@ void upap_authwithpeer(ppp_pcb *pcb, char *user, char *password);
 void upap_authpeer(ppp_pcb *pcb);
 #endif /* PPP_SERVER */
 
-extern struct protent pap_protent;
+extern const struct protent pap_protent;
 
 #endif /* UPAP_H */
 #endif /* PPP_SUPPORT && PAP_SUPPORT */
diff --git a/src/netif/ppp/auth.c b/src/netif/ppp/auth.c
index 43f172c0..d1dc41f8 100644
--- a/src/netif/ppp/auth.c
+++ b/src/netif/ppp/auth.c
@@ -709,7 +709,7 @@ void link_down(ppp_pcb *pcb) {
 
 void upper_layers_down(ppp_pcb *pcb) {
     int i;
-    struct protent *protp;
+    const struct protent *protp;
 
     for (i = 0; (protp = protocols[i]) != NULL; ++i) {
 	if (!protp->enabled_flag)
@@ -735,7 +735,7 @@ void link_established(ppp_pcb *pcb) {
 #endif /* PPP_SERVER */
     lcp_options *ho = &pcb->lcp_hisoptions;
     int i;
-    struct protent *protp;
+    const struct protent *protp;
 #if PPP_SERVER
     int errcode;
 #endif /* PPP_SERVER */
@@ -908,7 +908,7 @@ static void network_phase(ppp_pcb *pcb) {
 void start_networks(ppp_pcb *pcb) {
 #if CCP_SUPPORT || ECP_SUPPORT
     int i;
-    struct protent *protp;
+    const struct protent *protp;
 #endif /* CCP_SUPPORT || ECP_SUPPORT */
 #if ECP_SUPPORT
     int ecp_required;
@@ -974,7 +974,7 @@ void start_networks(ppp_pcb *pcb) {
 
 void continue_networks(ppp_pcb *pcb) {
     int i;
-    struct protent *protp;
+    const struct protent *protp;
 
     /*
      * Start the "real" network protocols.
diff --git a/src/netif/ppp/ccp.c b/src/netif/ppp/ccp.c
index 2117fcab..a5785329 100644
--- a/src/netif/ppp/ccp.c
+++ b/src/netif/ppp/ccp.c
@@ -180,7 +180,7 @@ static int  ccp_printpkt (u_char *pkt, int len,
 #endif /* PRINTPKT_SUPPORT */
 static void ccp_datainput (int unit, u_char *pkt, int len);
 
-struct protent ccp_protent = {
+const struct protent ccp_protent = {
     PPP_CCP,
     ccp_init,
     ccp_input,
diff --git a/src/netif/ppp/chap-new.c b/src/netif/ppp/chap-new.c
index 1adf5576..ec5a3050 100644
--- a/src/netif/ppp/chap-new.c
+++ b/src/netif/ppp/chap-new.c
@@ -634,7 +634,7 @@ static int chap_print_pkt(unsigned char *p, int plen,
 }
 #endif /* PRINTPKT_SUPPORT */
 
-struct protent chap_protent = {
+const struct protent chap_protent = {
 	PPP_CHAP,
 	chap_init,
 	chap_input,
diff --git a/src/netif/ppp/demand.c b/src/netif/ppp/demand.c
index dbabfa90..f31a124c 100644
--- a/src/netif/ppp/demand.c
+++ b/src/netif/ppp/demand.c
@@ -83,7 +83,7 @@ void
 demand_conf()
 {
     int i;
-    struct protent *protp;
+    const struct protent *protp;
 
 /*    framemax = lcp_allowoptions[0].mru;
     if (framemax < PPP_MRU) */
@@ -128,7 +128,7 @@ void
 demand_block()
 {
     int i;
-    struct protent *protp;
+    const struct protent *protp;
 
     for (i = 0; (protp = protocols[i]) != NULL; ++i)
 	if (protp->enabled_flag && protp->demand_conf != NULL)
@@ -145,7 +145,7 @@ demand_discard()
 {
     struct packet *pkt, *nextpkt;
     int i;
-    struct protent *protp;
+    const struct protent *protp;
 
     for (i = 0; (protp = protocols[i]) != NULL; ++i)
 	if (protp->enabled_flag && protp->demand_conf != NULL)
@@ -171,7 +171,7 @@ void
 demand_unblock()
 {
     int i;
-    struct protent *protp;
+    const struct protent *protp;
 
     for (i = 0; (protp = protocols[i]) != NULL; ++i)
 	if (protp->enabled_flag && protp->demand_conf != NULL)
@@ -436,7 +436,7 @@ active_packet(p, len)
     int len;
 {
     int proto, i;
-    struct protent *protp;
+    const struct protent *protp;
 
     if (len < PPP_HDRLEN)
 	return 0;
diff --git a/src/netif/ppp/eap.c b/src/netif/ppp/eap.c
index f0df3d08..b3106ad3 100644
--- a/src/netif/ppp/eap.c
+++ b/src/netif/ppp/eap.c
@@ -111,7 +111,7 @@ static int  eap_printpkt(u_char *inp, int inlen,
     void (*)(void *arg, char *fmt, ...), void *arg);
 #endif /* PRINTPKT_SUPPORT */
 
-struct protent eap_protent = {
+const struct protent eap_protent = {
 	PPP_EAP,		/* protocol number */
 	eap_init,		/* initialization procedure */
 	eap_input,		/* process a received packet */
diff --git a/src/netif/ppp/ecp.c b/src/netif/ppp/ecp.c
index f2645055..dc7e3127 100644
--- a/src/netif/ppp/ecp.c
+++ b/src/netif/ppp/ecp.c
@@ -99,7 +99,7 @@ static int  ecp_printpkt (u_char *pkt, int len,
 static void ecp_datainput (int unit, u_char *pkt, int len);
 */
 
-struct protent ecp_protent = {
+const struct protent ecp_protent = {
     PPP_ECP,
     ecp_init,
     NULL, /* ecp_input, */
diff --git a/src/netif/ppp/ipcp.c b/src/netif/ppp/ipcp.c
index ede4af8f..efb56a12 100644
--- a/src/netif/ppp/ipcp.c
+++ b/src/netif/ppp/ipcp.c
@@ -278,7 +278,7 @@ static int  ip_active_pkt (u_char *, int);
 static void create_resolv (u32_t, u32_t);
 #endif /* UNUSED */
 
-struct protent ipcp_protent = {
+const struct protent ipcp_protent = {
     PPP_IPCP,
     ipcp_init,
     ipcp_input,
diff --git a/src/netif/ppp/ipv6cp.c b/src/netif/ppp/ipv6cp.c
index 5318e2ba..96142ce0 100644
--- a/src/netif/ppp/ipv6cp.c
+++ b/src/netif/ppp/ipv6cp.c
@@ -274,7 +274,7 @@ static int ipv6cp_printpkt(u_char *p, int plen,
 static int ipv6_active_pkt(u_char *pkt, int len);
 #endif /* PPP_DEMAND */
 
-struct protent ipv6cp_protent = {
+const struct protent ipv6cp_protent = {
     PPP_IPV6CP,
     ipv6cp_init,
     ipv6cp_input,
diff --git a/src/netif/ppp/lcp.c b/src/netif/ppp/lcp.c
index 2d01831f..03783b05 100644
--- a/src/netif/ppp/lcp.c
+++ b/src/netif/ppp/lcp.c
@@ -272,7 +272,7 @@ static int lcp_printpkt(u_char *p, int plen,
 		void (*printer) (void *, char *, ...), void *arg);
 #endif /* PRINTPKT_SUPPORT */
 
-struct protent lcp_protent = {
+const struct protent lcp_protent = {
     PPP_LCP,
     lcp_init,
     lcp_input,
@@ -592,7 +592,7 @@ static int lcp_extcode(fsm *f, int code, int id, u_char *inp, int len) {
  */
 static void lcp_rprotrej(fsm *f, u_char *inp, int len) {
     int i;
-    struct protent *protp;
+    const struct protent *protp;
     u_short prot;
 #if PPP_PROTOCOLNAME
     const char *pname;
diff --git a/src/netif/ppp/ppp.c b/src/netif/ppp/ppp.c
index ba2cc443..bb7e7add 100644
--- a/src/netif/ppp/ppp.c
+++ b/src/netif/ppp/ppp.c
@@ -152,7 +152,7 @@ int link_stats_valid;
  * One entry per supported protocol.
  * The last entry must be NULL.
  */
-struct protent *protocols[] = {
+const struct protent* const protocols[] = {
     &lcp_protent,
 #if PAP_SUPPORT
     &pap_protent,
@@ -599,7 +599,7 @@ int ppp_delete(ppp_pcb *pcb) {
 
 /* Set a PPP PCB to its initial state */
 static void ppp_clear(ppp_pcb *pcb) {
-  struct protent *protp;
+  const struct protent *protp;
   int i;
 
   LWIP_ASSERT("pcb->phase == PHASE_DEAD || pcb->phase == PHASE_HOLDOFF", pcb->phase == PHASE_DEAD || pcb->phase == PHASE_HOLDOFF);
@@ -769,7 +769,7 @@ void ppp_input(ppp_pcb *pcb, struct pbuf *pb) {
     default: {
 
       int i;
-      struct protent *protp;
+      const struct protent *protp;
       /*
        * Upcall the proper protocol input routine.
        */
diff --git a/src/netif/ppp/upap.c b/src/netif/ppp/upap.c
index 221b9c36..5e61a76c 100644
--- a/src/netif/ppp/upap.c
+++ b/src/netif/ppp/upap.c
@@ -89,7 +89,7 @@ static void upap_protrej(ppp_pcb *pcb);
 static int upap_printpkt(u_char *p, int plen, void (*printer) (void *, char *, ...), void *arg);
 #endif /* PRINTPKT_SUPPORT */
 
-struct protent pap_protent = {
+const struct protent pap_protent = {
     PPP_PAP,
     upap_init,
     upap_input,
diff --git a/src/netif/ppp/utils.c b/src/netif/ppp/utils.c
index f918ba07..c7a78c7c 100644
--- a/src/netif/ppp/utils.c
+++ b/src/netif/ppp/utils.c
@@ -455,7 +455,7 @@ static void ppp_format_packet(u_char *p, int len,
 		void (*printer) (void *, char *, ...), void *arg) {
     int i, n;
     u_short proto;
-    struct protent *protp;
+    const struct protent *protp;
 
     if (len >= 2) {
 	GETSHORT(proto, p);