diff --git a/CHANGELOG b/CHANGELOG
index 151d49fc..31b25961 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -6,6 +6,11 @@ HISTORY
 
   ++ New features:
 
+  2015-02-22: chrysn, Simon Goldschmidt
+  * *.*: Changed nearly all functions taking 'ip(X)_addr_t' pointer to take
+    const pointers (changed user callbacks: raw_recv_fn, udp_recv_fn; changed
+    port callbacks: netif_output_fn, netif_igmp_mac_filter_fn)
+
   2015-02-19: Ivan Delamer
   * netif.h, dhcp.c: Removed unused netif flag for DHCP. The preferred way to evaluate
     if DHCP is active is through netif->dhcp field.
diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index ce793f13..ecd2d912 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -196,7 +196,7 @@ netconn_getaddr(struct netconn *conn, ip_addr_t *addr, u16_t *port, u8_t local)
  * @return ERR_OK if bound, any other err_t on failure
  */
 err_t
-netconn_bind(struct netconn *conn, ip_addr_t *addr, u16_t port)
+netconn_bind(struct netconn *conn, const ip_addr_t *addr, u16_t port)
 {
   API_MSG_VAR_DECLARE(msg);
   err_t err;
@@ -228,7 +228,7 @@ netconn_bind(struct netconn *conn, ip_addr_t *addr, u16_t port)
  * @return ERR_OK if connected, return value of tcp_/udp_/raw_connect otherwise
  */
 err_t
-netconn_connect(struct netconn *conn, ip_addr_t *addr, u16_t port)
+netconn_connect(struct netconn *conn, const ip_addr_t *addr, u16_t port)
 {
   API_MSG_VAR_DECLARE(msg);
   err_t err;
@@ -626,7 +626,7 @@ netconn_recved(struct netconn *conn, u32_t length)
  * @return ERR_OK if data was sent, any other err_t on error
  */
 err_t
-netconn_sendto(struct netconn *conn, struct netbuf *buf, ip_addr_t *addr, u16_t port)
+netconn_sendto(struct netconn *conn, struct netbuf *buf, const ip_addr_t *addr, u16_t port)
 {
   if (buf != NULL) {
     ipX_addr_set_ipaddr(PCB_ISIPV6(conn->pcb.ip), &buf->addr, addr);
@@ -806,8 +806,8 @@ netconn_shutdown(struct netconn *conn, u8_t shut_rx, u8_t shut_tx)
  */
 err_t
 netconn_join_leave_group(struct netconn *conn,
-                         ip_addr_t *multiaddr,
-                         ip_addr_t *netif_addr,
+                         const ip_addr_t *multiaddr,
+                         const ip_addr_t *netif_addr,
                          enum netconn_igmp join_or_leave)
 {
   API_MSG_VAR_DECLARE(msg);
diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index 3fe7673f..73bf782d 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -80,7 +80,7 @@ static err_t lwip_netconn_do_close_internal(struct netconn *conn);
  */
 static u8_t
 recv_raw(void *arg, struct raw_pcb *pcb, struct pbuf *p,
-    ip_addr_t *addr)
+    const ip_addr_t *addr)
 {
   struct pbuf *q;
   struct netbuf *buf;
@@ -146,7 +146,7 @@ recv_raw(void *arg, struct raw_pcb *pcb, struct pbuf *p,
  */
 static void
 recv_udp(void *arg, struct udp_pcb *pcb, struct pbuf *p,
-   ip_addr_t *addr, u16_t port)
+   const ip_addr_t *addr, u16_t port)
 {
   struct netbuf *buf;
   struct netconn *conn;
diff --git a/src/core/dhcp.c b/src/core/dhcp.c
index 8e676db0..05b55157 100644
--- a/src/core/dhcp.c
+++ b/src/core/dhcp.c
@@ -179,7 +179,7 @@ static err_t dhcp_reboot(struct netif *netif);
 static void dhcp_set_state(struct dhcp *dhcp, u8_t new_state);
 
 /* receive, unfold, parse and free incoming messages */
-static void dhcp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port);
+static void dhcp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port);
 
 /* set the DHCP timers */
 static void dhcp_timeout(struct netif *netif);
@@ -1581,7 +1581,7 @@ decode_next:
  * If an incoming DHCP message is in response to us, then trigger the state machine
  */
 static void
-dhcp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
+dhcp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
 {
   struct netif *netif = (struct netif *)arg;
   struct dhcp *dhcp = netif->dhcp;
diff --git a/src/core/dns.c b/src/core/dns.c
index 45b416b4..44513c9a 100644
--- a/src/core/dns.c
+++ b/src/core/dns.c
@@ -277,7 +277,7 @@ static void dns_init_local();
 
 
 /* forward declarations */
-static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port);
+static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port);
 static void dns_check_entries(void);
 
 /*-----------------------------------------------------------------------------
@@ -979,7 +979,7 @@ dns_check_entries(void)
  * @params see udp.h
  */
 static void
-dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
+dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
 {
   u8_t i, entry_idx = DNS_TABLE_SIZE;
   u16_t txid;
diff --git a/src/core/inet_chksum.c b/src/core/inet_chksum.c
index 9f68e472..8124523e 100644
--- a/src/core/inet_chksum.c
+++ b/src/core/inet_chksum.c
@@ -340,7 +340,7 @@ inet_chksum_pseudo(struct pbuf *p, u8_t proto, u16_t proto_len,
  */
 u16_t
 ip6_chksum_pseudo(struct pbuf *p, u8_t proto, u16_t proto_len,
-       ip6_addr_t *src, ip6_addr_t *dest)
+       const ip6_addr_t *src, const ip6_addr_t *dest)
 {
   u32_t acc = 0;
   u32_t addr;
@@ -455,7 +455,7 @@ inet_chksum_pseudo_partial(struct pbuf *p, u8_t proto, u16_t proto_len,
  */
 u16_t
 ip6_chksum_pseudo_partial(struct pbuf *p, u8_t proto, u16_t proto_len,
-       u16_t chksum_len, ip6_addr_t *src, ip6_addr_t *dest)
+       u16_t chksum_len, const ip6_addr_t *src, const ip6_addr_t *dest)
 {
   u32_t acc = 0;
   u32_t addr;
diff --git a/src/core/ipv4/igmp.c b/src/core/ipv4/igmp.c
index 3003c6b7..8fbae299 100644
--- a/src/core/ipv4/igmp.c
+++ b/src/core/ipv4/igmp.c
@@ -135,7 +135,7 @@ PACK_STRUCT_END
 #endif
 
 
-static struct igmp_group *igmp_lookup_group(struct netif *ifp, ip_addr_t *addr);
+static struct igmp_group *igmp_lookup_group(struct netif *ifp, const ip_addr_t *addr);
 static err_t  igmp_remove_group(struct igmp_group *group);
 static void   igmp_timeout( struct igmp_group *group);
 static void   igmp_start_timer(struct igmp_group *group, u8_t max_time);
@@ -287,7 +287,7 @@ igmp_report_groups(struct netif *netif)
  *         NULL if the group wasn't found.
  */
 struct igmp_group *
-igmp_lookfor_group(struct netif *ifp, ip_addr_t *addr)
+igmp_lookfor_group(struct netif *ifp, const ip_addr_t *addr)
 {
   struct igmp_group *group = igmp_group_list;
 
@@ -313,7 +313,7 @@ igmp_lookfor_group(struct netif *ifp, ip_addr_t *addr)
  *         NULL on memory error.
  */
 struct igmp_group *
-igmp_lookup_group(struct netif *ifp, ip_addr_t *addr)
+igmp_lookup_group(struct netif *ifp, const ip_addr_t *addr)
 {
   struct igmp_group *group = igmp_group_list;
   
@@ -386,7 +386,7 @@ igmp_remove_group(struct igmp_group *group)
  * @param dest destination ip address of the igmp packet
  */
 void
-igmp_input(struct pbuf *p, struct netif *inp, ip_addr_t *dest)
+igmp_input(struct pbuf *p, struct netif *inp, const ip_addr_t *dest)
 {
   struct igmp_msg*   igmp;
   struct igmp_group* group;
@@ -510,7 +510,7 @@ igmp_input(struct pbuf *p, struct netif *inp, ip_addr_t *dest)
  * @return ERR_OK if group was joined on the netif(s), an err_t otherwise
  */
 err_t
-igmp_joingroup(ip_addr_t *ifaddr, ip_addr_t *groupaddr)
+igmp_joingroup(const ip_addr_t *ifaddr, const ip_addr_t *groupaddr)
 {
   err_t              err = ERR_VAL; /* no matching interface */
   struct igmp_group *group;
@@ -580,7 +580,7 @@ igmp_joingroup(ip_addr_t *ifaddr, ip_addr_t *groupaddr)
  * @return ERR_OK if group was left on the netif(s), an err_t otherwise
  */
 err_t
-igmp_leavegroup(ip_addr_t *ifaddr, ip_addr_t *groupaddr)
+igmp_leavegroup(const ip_addr_t *ifaddr, const ip_addr_t *groupaddr)
 {
   err_t              err = ERR_VAL; /* no matching interface */
   struct igmp_group *group;
diff --git a/src/core/ipv6/ethip6.c b/src/core/ipv6/ethip6.c
index d9ac30f6..eedc1f9a 100644
--- a/src/core/ipv6/ethip6.c
+++ b/src/core/ipv6/ethip6.c
@@ -133,7 +133,7 @@ ethip6_send(struct netif *netif, struct pbuf *p, struct eth_addr *src, struct et
  * or the return type of either etharp_query() or etharp_send_ip().
  */
 err_t
-ethip6_output(struct netif *netif, struct pbuf *q, ip6_addr_t *ip6addr)
+ethip6_output(struct netif *netif, struct pbuf *q, const ip6_addr_t *ip6addr)
 {
   struct eth_addr dest;
   s8_t i;
diff --git a/src/core/ipv6/ip6.c b/src/core/ipv6/ip6.c
index 85a61804..d934950f 100644
--- a/src/core/ipv6/ip6.c
+++ b/src/core/ipv6/ip6.c
@@ -78,7 +78,7 @@
  * @return the netif on which to send to reach dest
  */
 struct netif *
-ip6_route(struct ip6_addr *src, struct ip6_addr *dest)
+ip6_route(const struct ip6_addr *src, const struct ip6_addr *dest)
 {
   struct netif *netif;
   s8_t i;
@@ -156,7 +156,7 @@ ip6_route(struct ip6_addr *src, struct ip6_addr *dest)
  *         source address is found
  */
 ip6_addr_t *
-ip6_select_source_address(struct netif *netif, ip6_addr_t * dest)
+ip6_select_source_address(struct netif *netif, const ip6_addr_t * dest)
 {
   ip6_addr_t * src = NULL;
   u8_t i;
@@ -744,11 +744,11 @@ ip6_input_cleanup:
  *         returns errors returned by netif->output
  */
 err_t
-ip6_output_if(struct pbuf *p, ip6_addr_t *src, ip6_addr_t *dest,
+ip6_output_if(struct pbuf *p, const ip6_addr_t *src, const ip6_addr_t *dest,
              u8_t hl, u8_t tc,
              u8_t nexth, struct netif *netif)
 {
-  ip6_addr_t *src_used = src;
+  const ip6_addr_t *src_used = src;
   if (dest != IP_HDRINCL) {
     if (src != NULL && ip6_addr_isany(src)) {
       src = ip6_select_source_address(netif, dest);
@@ -768,7 +768,7 @@ ip6_output_if(struct pbuf *p, ip6_addr_t *src, ip6_addr_t *dest,
  * when it is 'any'.
  */
 err_t
-ip6_output_if_src(struct pbuf *p, ip6_addr_t *src, ip6_addr_t *dest,
+ip6_output_if_src(struct pbuf *p, const ip6_addr_t *src, const ip6_addr_t *dest,
              u8_t hl, u8_t tc,
              u8_t nexth, struct netif *netif)
 {
diff --git a/src/core/ipv6/mld6.c b/src/core/ipv6/mld6.c
index 0771f5c8..0279b169 100644
--- a/src/core/ipv6/mld6.c
+++ b/src/core/ipv6/mld6.c
@@ -76,7 +76,7 @@ static struct mld_group* mld_group_list;
 
 
 /* Forward declarations. */
-static struct mld_group * mld6_new_group(struct netif *ifp, ip6_addr_t *addr);
+static struct mld_group * mld6_new_group(struct netif *ifp, const ip6_addr_t *addr);
 static err_t mld6_free_group(struct mld_group *group);
 static void mld6_delayed_report(struct mld_group *group, u16_t maxresp);
 static void mld6_send(struct mld_group *group, u8_t type);
@@ -150,7 +150,7 @@ mld6_report_groups(struct netif *netif)
  *         NULL if the group wasn't found.
  */
 struct mld_group *
-mld6_lookfor_group(struct netif *ifp, ip6_addr_t *addr)
+mld6_lookfor_group(struct netif *ifp, const ip6_addr_t *addr)
 {
   struct mld_group *group = mld_group_list;
 
@@ -174,7 +174,7 @@ mld6_lookfor_group(struct netif *ifp, ip6_addr_t *addr)
  *         NULL on memory error.
  */
 static struct mld_group *
-mld6_new_group(struct netif *ifp, ip6_addr_t *addr)
+mld6_new_group(struct netif *ifp, const ip6_addr_t *addr)
 {
   struct mld_group *group;
 
@@ -324,7 +324,7 @@ mld6_input(struct pbuf *p, struct netif *inp)
  * @return ERR_OK if group was joined on the netif(s), an err_t otherwise
  */
 err_t
-mld6_joingroup(ip6_addr_t *srcaddr, ip6_addr_t *groupaddr)
+mld6_joingroup(const ip6_addr_t *srcaddr, const ip6_addr_t *groupaddr)
 {
   err_t              err = ERR_VAL; /* no matching interface */
   struct mld_group  *group;
@@ -391,7 +391,7 @@ mld6_joingroup(ip6_addr_t *srcaddr, ip6_addr_t *groupaddr)
  * @return ERR_OK if group was left on the netif(s), an err_t otherwise
  */
 err_t
-mld6_leavegroup(ip6_addr_t *srcaddr, ip6_addr_t *groupaddr)
+mld6_leavegroup(const ip6_addr_t *srcaddr, const ip6_addr_t *groupaddr)
 {
   err_t              err = ERR_VAL; /* no matching interface */
   struct mld_group  *group;
diff --git a/src/core/ipv6/nd6.c b/src/core/ipv6/nd6.c
index d3dc6ca8..a67f1b6a 100644
--- a/src/core/ipv6/nd6.c
+++ b/src/core/ipv6/nd6.c
@@ -82,21 +82,21 @@ static ip6_addr_t multicast_address;
 static u8_t nd6_ra_buffer[sizeof(struct prefix_option)];
 
 /* Forward declarations. */
-static s8_t nd6_find_neighbor_cache_entry(ip6_addr_t * ip6addr);
+static s8_t nd6_find_neighbor_cache_entry(const ip6_addr_t * ip6addr);
 static s8_t nd6_new_neighbor_cache_entry(void);
 static void nd6_free_neighbor_cache_entry(s8_t i);
-static s8_t nd6_find_destination_cache_entry(ip6_addr_t * ip6addr);
+static s8_t nd6_find_destination_cache_entry(const ip6_addr_t * ip6addr);
 static s8_t nd6_new_destination_cache_entry(void);
-static s8_t nd6_is_prefix_in_netif(ip6_addr_t * ip6addr, struct netif * netif);
-static s8_t nd6_get_router(ip6_addr_t * router_addr, struct netif * netif);
-static s8_t nd6_new_router(ip6_addr_t * router_addr, struct netif * netif);
+static s8_t nd6_is_prefix_in_netif(const ip6_addr_t * ip6addr, struct netif * netif);
+static s8_t nd6_get_router(const ip6_addr_t * router_addr, struct netif * netif);
+static s8_t nd6_new_router(const ip6_addr_t * router_addr, struct netif * netif);
 static s8_t nd6_get_onlink_prefix(ip6_addr_t * prefix, struct netif * netif);
 static s8_t nd6_new_onlink_prefix(ip6_addr_t * prefix, struct netif * netif);
 
 #define ND6_SEND_FLAG_MULTICAST_DEST 0x01
 #define ND6_SEND_FLAG_ALLNODES_DEST 0x02
-static void nd6_send_ns(struct netif * netif, ip6_addr_t * target_addr, u8_t flags);
-static void nd6_send_na(struct netif * netif, ip6_addr_t * target_addr, u8_t flags);
+static void nd6_send_ns(struct netif * netif, const ip6_addr_t * target_addr, u8_t flags);
+static void nd6_send_na(struct netif * netif, const ip6_addr_t * target_addr, u8_t flags);
 #if LWIP_IPV6_SEND_ROUTER_SOLICIT
 static void nd6_send_rs(struct netif * netif);
 #endif /* LWIP_IPV6_SEND_ROUTER_SOLICIT */
@@ -794,7 +794,7 @@ nd6_tmr(void)
  * @param flags one of ND6_SEND_FLAG_*
  */
 static void
-nd6_send_ns(struct netif * netif, ip6_addr_t * target_addr, u8_t flags)
+nd6_send_ns(struct netif * netif, const ip6_addr_t * target_addr, u8_t flags)
 {
   struct ns_header * ns_hdr;
   struct lladdr_option * lladdr_opt;
@@ -859,13 +859,13 @@ nd6_send_ns(struct netif * netif, ip6_addr_t * target_addr, u8_t flags)
  * @param flags one of ND6_SEND_FLAG_*
  */
 static void
-nd6_send_na(struct netif * netif, ip6_addr_t * target_addr, u8_t flags)
+nd6_send_na(struct netif * netif, const ip6_addr_t * target_addr, u8_t flags)
 {
   struct na_header * na_hdr;
   struct lladdr_option * lladdr_opt;
   struct pbuf * p;
-  ip6_addr_t * src_addr;
-  ip6_addr_t * dest_addr;
+  const ip6_addr_t * src_addr;
+  const ip6_addr_t * dest_addr;
 
   /* Use link-local address as source address. */
   /* src_addr = &(netif->ip6_addr[0]); */
@@ -1003,7 +1003,7 @@ nd6_send_rs(struct netif * netif)
  * entry is found
  */
 static s8_t
-nd6_find_neighbor_cache_entry(ip6_addr_t * ip6addr)
+nd6_find_neighbor_cache_entry(const ip6_addr_t * ip6addr)
 {
   s8_t i;
   for (i = 0; i < LWIP_ND6_NUM_NEIGHBORS; i++) {
@@ -1158,7 +1158,7 @@ nd6_free_neighbor_cache_entry(s8_t i)
  * entry is found
  */
 static s8_t
-nd6_find_destination_cache_entry(ip6_addr_t * ip6addr)
+nd6_find_destination_cache_entry(const ip6_addr_t * ip6addr)
 {
   s8_t i;
   for (i = 0; i < LWIP_ND6_NUM_DESTINATIONS; i++) {
@@ -1208,7 +1208,7 @@ nd6_new_destination_cache_entry(void)
  * @return 1 if the address is on-link, 0 otherwise
  */
 static s8_t
-nd6_is_prefix_in_netif(ip6_addr_t * ip6addr, struct netif * netif)
+nd6_is_prefix_in_netif(const ip6_addr_t * ip6addr, struct netif * netif)
 {
   s8_t i;
   for (i = 0; i < LWIP_ND6_NUM_PREFIXES; i++) {
@@ -1237,7 +1237,7 @@ nd6_is_prefix_in_netif(ip6_addr_t * ip6addr, struct netif * netif)
  *         router is found
  */
 s8_t
-nd6_select_router(ip6_addr_t * ip6addr, struct netif * netif)
+nd6_select_router(const ip6_addr_t * ip6addr, struct netif * netif)
 {
   s8_t i;
   /* last_router is used for round-robin router selection (as recommended
@@ -1296,7 +1296,7 @@ nd6_select_router(ip6_addr_t * ip6addr, struct netif * netif)
  * @return the index of the router entry, or -1 if not found
  */
 static s8_t
-nd6_get_router(ip6_addr_t * router_addr, struct netif * netif)
+nd6_get_router(const ip6_addr_t * router_addr, struct netif * netif)
 {
   s8_t i;
 
@@ -1321,7 +1321,7 @@ nd6_get_router(ip6_addr_t * router_addr, struct netif * netif)
  * @return the index on the router table, or -1 if could not be created
  */
 static s8_t
-nd6_new_router(ip6_addr_t * router_addr, struct netif * netif)
+nd6_new_router(const ip6_addr_t * router_addr, struct netif * netif)
 {
   s8_t router_index;
   s8_t neighbor_index;
@@ -1427,7 +1427,7 @@ nd6_new_onlink_prefix(ip6_addr_t * prefix, struct netif * netif)
  *         could be created
  */
 s8_t
-nd6_get_next_hop_entry(ip6_addr_t * ip6addr, struct netif * netif)
+nd6_get_next_hop_entry(const ip6_addr_t * ip6addr, struct netif * netif)
 {
   s8_t i;
 
@@ -1726,7 +1726,7 @@ nd6_send_q(s8_t i)
  * @return the Path MTU, if known, or the netif default MTU
  */
 u16_t
-nd6_get_destination_mtu(ip6_addr_t * ip6addr, struct netif * netif)
+nd6_get_destination_mtu(const ip6_addr_t * ip6addr, struct netif * netif)
 {
   s8_t i;
 
@@ -1756,7 +1756,7 @@ nd6_get_destination_mtu(ip6_addr_t * ip6addr, struct netif * netif)
  *                by an upper layer protocol (TCP)
  */
 void
-nd6_reachability_hint(ip6_addr_t * ip6addr)
+nd6_reachability_hint(const ip6_addr_t * ip6addr)
 {
   s8_t i;
 
diff --git a/src/core/netif.c b/src/core/netif.c
index 82442f3d..328694c4 100644
--- a/src/core/netif.c
+++ b/src/core/netif.c
@@ -85,7 +85,7 @@ struct netif *netif_default;
 static u8_t netif_num;
 
 #if LWIP_IPV6
-static err_t netif_null_output_ip6(struct netif *netif, struct pbuf *p, ip6_addr_t *ipaddr);
+static err_t netif_null_output_ip6(struct netif *netif, struct pbuf *p, const ip6_addr_t *ipaddr);
 #endif /* LWIP_IPV6 */
 
 #if LWIP_IPV6
@@ -97,7 +97,7 @@ static err_t netif_null_output_ip6(struct netif *netif, struct pbuf *p, ip6_addr
 #if LWIP_HAVE_LOOPIF
 static err_t netif_loop_output_ipv4(struct netif *netif, struct pbuf *p, const ip_addr_t* addr);
 #if LWIP_IPV6
-static err_t netif_loop_output_ipv6(struct netif *netif, struct pbuf *p, ip6_addr_t* addr);
+static err_t netif_loop_output_ipv6(struct netif *netif, struct pbuf *p, const ip6_addr_t* addr);
 #endif
 
 
@@ -771,7 +771,7 @@ netif_loop_output_ipv4(struct netif *netif, struct pbuf *p, const ip_addr_t* add
 
 #if LWIP_IPV6
 static err_t
-netif_loop_output_ipv6(struct netif *netif, struct pbuf *p, ip6_addr_t* addr)
+netif_loop_output_ipv6(struct netif *netif, struct pbuf *p, const ip6_addr_t* addr)
 {
   LWIP_UNUSED_ARG(addr);
   return netif_loop_output(netif, p);
@@ -929,7 +929,7 @@ netif_create_ip6_linklocal_address(struct netif * netif, u8_t from_mac_48bit)
 }
 
 static err_t
-netif_null_output_ip6(struct netif *netif, struct pbuf *p, ip6_addr_t *ipaddr)
+netif_null_output_ip6(struct netif *netif, struct pbuf *p, const ip6_addr_t *ipaddr)
 {
     (void)netif;
     (void)p;
diff --git a/src/core/snmp/msg_in.c b/src/core/snmp/msg_in.c
index 08c5b346..57457b51 100644
--- a/src/core/snmp/msg_in.c
+++ b/src/core/snmp/msg_in.c
@@ -64,7 +64,7 @@ struct snmp_msg_pstat msg_input_list[SNMP_CONCURRENT_REQUESTS];
 /* UDP Protocol Control Block */
 struct udp_pcb *snmp1_pcb;
 
-static void snmp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port);
+static void snmp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port);
 static err_t snmp_pdu_header_check(struct pbuf *p, u16_t ofs, u16_t pdu_len, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat);
 static err_t snmp_pdu_dec_varbindlist(struct pbuf *p, u16_t ofs, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat);
 
@@ -901,7 +901,7 @@ snmp_msg_event(u8_t request_id)
 
 /* lwIP UDP receive callback function */
 static void
-snmp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
+snmp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
 {
   struct snmp_msg_pstat *msg_ps;
   u8_t req_idx;
diff --git a/src/include/lwip/api.h b/src/include/lwip/api.h
index c0145a66..4dde3e2e 100644
--- a/src/include/lwip/api.h
+++ b/src/include/lwip/api.h
@@ -263,8 +263,8 @@ LWIP_NETCONN_SCOPE err_t   netconn_getaddr(struct netconn *conn, ip_addr_t *addr
 #define netconn_peer(c,i,p) netconn_getaddr(c,i,p,0)
 #define netconn_addr(c,i,p) netconn_getaddr(c,i,p,1)
 
-LWIP_NETCONN_SCOPE err_t   netconn_bind(struct netconn *conn, ip_addr_t *addr, u16_t port);
-LWIP_NETCONN_SCOPE err_t   netconn_connect(struct netconn *conn, ip_addr_t *addr, u16_t port);
+LWIP_NETCONN_SCOPE err_t   netconn_bind(struct netconn *conn, const ip_addr_t *addr, u16_t port);
+LWIP_NETCONN_SCOPE err_t   netconn_connect(struct netconn *conn, const ip_addr_t *addr, u16_t port);
 LWIP_NETCONN_SCOPE err_t   netconn_disconnect (struct netconn *conn);
 LWIP_NETCONN_SCOPE err_t   netconn_listen_with_backlog(struct netconn *conn, u8_t backlog);
 #define netconn_listen(conn) netconn_listen_with_backlog(conn, TCP_DEFAULT_LISTEN_BACKLOG)
@@ -273,7 +273,7 @@ LWIP_NETCONN_SCOPE err_t   netconn_recv(struct netconn *conn, struct netbuf **ne
 LWIP_NETCONN_SCOPE err_t   netconn_recv_tcp_pbuf(struct netconn *conn, struct pbuf **new_buf);
 LWIP_NETCONN_SCOPE void    netconn_recved(struct netconn *conn, u32_t length);
 LWIP_NETCONN_SCOPE err_t   netconn_sendto(struct netconn *conn, struct netbuf *buf,
-                       ip_addr_t *addr, u16_t port);
+                             const ip_addr_t *addr, u16_t port);
 LWIP_NETCONN_SCOPE err_t   netconn_send(struct netconn *conn, struct netbuf *buf);
 LWIP_NETCONN_SCOPE err_t   netconn_write_partly(struct netconn *conn, const void *dataptr, size_t size,
                              u8_t apiflags, size_t *bytes_written);
@@ -283,8 +283,8 @@ LWIP_NETCONN_SCOPE err_t   netconn_close(struct netconn *conn);
 LWIP_NETCONN_SCOPE err_t   netconn_shutdown(struct netconn *conn, u8_t shut_rx, u8_t shut_tx);
 
 #if LWIP_IGMP || (LWIP_IPV6 && LWIP_IPV6_MLD)
-LWIP_NETCONN_SCOPE err_t   netconn_join_leave_group(struct netconn *conn, ip_addr_t *multiaddr,
-                                 ip_addr_t *netif_addr, enum netconn_igmp join_or_leave);
+LWIP_NETCONN_SCOPE err_t   netconn_join_leave_group(struct netconn *conn, const ip_addr_t *multiaddr,
+                             const ip_addr_t *netif_addr, enum netconn_igmp join_or_leave);
 #endif /* LWIP_IGMP || (LWIP_IPV6 && LWIP_IPV6_MLD) */
 #if LWIP_DNS
 err_t   netconn_gethostbyname(const char *name, ip_addr_t *addr);
diff --git a/src/include/lwip/api_msg.h b/src/include/lwip/api_msg.h
index e602a1af..7dcf01a4 100644
--- a/src/include/lwip/api_msg.h
+++ b/src/include/lwip/api_msg.h
@@ -56,9 +56,11 @@ extern "C" {
 #endif
 
 #if LWIP_MPU_COMPATIBLE
-#define API_MSG_M_DEF(m)  m
+#define API_MSG_M_DEF(m)      m
+#define API_MSG_M_DEF_C(t, m) t m
 #else /* LWIP_MPU_COMPATIBLE */
-#define API_MSG_M_DEF(m)  *m
+#define API_MSG_M_DEF(m)      *m
+#define API_MSG_M_DEF_C(t, m) const t * m
 #endif /* LWIP_MPU_COMPATIBLE */
 
 /* For the netconn API, these values are use as a bitmask! */
@@ -88,7 +90,7 @@ struct api_msg_msg {
     } n;
     /** used for lwip_netconn_do_bind and lwip_netconn_do_connect */
     struct {
-      ip_addr_t API_MSG_M_DEF(ipaddr);
+      API_MSG_M_DEF_C(ip_addr_t, ipaddr);
       u16_t port;
     } bc;
     /** used for lwip_netconn_do_getaddr */
@@ -122,8 +124,8 @@ struct api_msg_msg {
 #if LWIP_IGMP || (LWIP_IPV6 && LWIP_IPV6_MLD)
     /** used for lwip_netconn_do_join_leave_group */
     struct {
-      ipX_addr_t API_MSG_M_DEF(multiaddr);
-      ipX_addr_t API_MSG_M_DEF(netif_addr);
+      API_MSG_M_DEF_C(ipX_addr_t, multiaddr);
+      API_MSG_M_DEF_C(ipX_addr_t, netif_addr);
       enum netconn_igmp join_or_leave;
     } jl;
 #endif /* LWIP_IGMP || (LWIP_IPV6 && LWIP_IPV6_MLD) */
@@ -167,7 +169,7 @@ struct dns_api_msg {
 #else /* LWIP_MPU_COMPATIBLE */
   const char *name;
 #endif /* LWIP_MPU_COMPATIBLE */
-  /** Rhe resolved address is stored here */
+  /** The resolved address is stored here */
   ip_addr_t API_MSG_M_DEF(addr);
   /** This semaphore is posted when the name is resolved, the application thread
       should wait on it. */
diff --git a/src/include/lwip/ethip6.h b/src/include/lwip/ethip6.h
index 31fed183..5e88dffd 100644
--- a/src/include/lwip/ethip6.h
+++ b/src/include/lwip/ethip6.h
@@ -57,7 +57,7 @@ extern "C" {
 #endif
 
 
-err_t ethip6_output(struct netif *netif, struct pbuf *q, ip6_addr_t *ip6addr);
+err_t ethip6_output(struct netif *netif, struct pbuf *q, const ip6_addr_t *ip6addr);
 
 #ifdef __cplusplus
 }
diff --git a/src/include/lwip/igmp.h b/src/include/lwip/igmp.h
index 4687b1fd..32e770ef 100644
--- a/src/include/lwip/igmp.h
+++ b/src/include/lwip/igmp.h
@@ -91,10 +91,10 @@ void   igmp_init(void);
 err_t  igmp_start(struct netif *netif);
 err_t  igmp_stop(struct netif *netif);
 void   igmp_report_groups(struct netif *netif);
-struct igmp_group *igmp_lookfor_group(struct netif *ifp, ip_addr_t *addr);
-void   igmp_input(struct pbuf *p, struct netif *inp, ip_addr_t *dest);
-err_t  igmp_joingroup(ip_addr_t *ifaddr, ip_addr_t *groupaddr);
-err_t  igmp_leavegroup(ip_addr_t *ifaddr, ip_addr_t *groupaddr);
+struct igmp_group *igmp_lookfor_group(struct netif *ifp, const ip_addr_t *addr);
+void   igmp_input(struct pbuf *p, struct netif *inp, const ip_addr_t *dest);
+err_t  igmp_joingroup(const ip_addr_t *ifaddr, const ip_addr_t *groupaddr);
+err_t  igmp_leavegroup(const ip_addr_t *ifaddr, const ip_addr_t *groupaddr);
 void   igmp_tmr(void);
 
 #ifdef __cplusplus
diff --git a/src/include/lwip/inet_chksum.h b/src/include/lwip/inet_chksum.h
index e40f2169..4ae38ee1 100644
--- a/src/include/lwip/inet_chksum.h
+++ b/src/include/lwip/inet_chksum.h
@@ -82,9 +82,9 @@ u16_t lwip_chksum_copy(void *dst, const void *src, u16_t len);
 
 #if LWIP_IPV6
 u16_t ip6_chksum_pseudo(struct pbuf *p, u8_t proto, u16_t proto_len,
-       ip6_addr_t *src, ip6_addr_t *dest);
+       const ip6_addr_t *src, const ip6_addr_t *dest);
 u16_t ip6_chksum_pseudo_partial(struct pbuf *p, u8_t proto, u16_t proto_len,
-       u16_t chksum_len, ip6_addr_t *src, ip6_addr_t *dest);
+       u16_t chksum_len, const ip6_addr_t *src, const ip6_addr_t *dest);
 
 #define ipX_chksum_pseudo(isipv6, p, proto, proto_len, src, dest) \
   ((isipv6) ? \
diff --git a/src/include/lwip/ip6.h b/src/include/lwip/ip6.h
index a7b264f0..c650dbfe 100644
--- a/src/include/lwip/ip6.h
+++ b/src/include/lwip/ip6.h
@@ -162,17 +162,17 @@ PACK_STRUCT_END
 
 
 #define ip6_init() /* TODO should we init current addresses and header pointer? */
-struct netif *ip6_route(struct ip6_addr *src, struct ip6_addr *dest);
-ip6_addr_t   *ip6_select_source_address(struct netif *netif, ip6_addr_t * dest);
+struct netif *ip6_route(const struct ip6_addr *src, const struct ip6_addr *dest);
+ip6_addr_t   *ip6_select_source_address(struct netif *netif, const ip6_addr_t * dest);
 err_t         ip6_input(struct pbuf *p, struct netif *inp);
 err_t         ip6_output(struct pbuf *p, struct ip6_addr *src, struct ip6_addr *dest,
                          u8_t hl, u8_t tc, u8_t nexth);
-err_t         ip6_output_if(struct pbuf *p, struct ip6_addr *src, struct ip6_addr *dest,
+err_t         ip6_output_if(struct pbuf *p, const struct ip6_addr *src, const struct ip6_addr *dest,
                             u8_t hl, u8_t tc, u8_t nexth, struct netif *netif);
-err_t         ip6_output_if_src(struct pbuf *p, struct ip6_addr *src, struct ip6_addr *dest,
+err_t         ip6_output_if_src(struct pbuf *p, const struct ip6_addr *src, const struct ip6_addr *dest,
                             u8_t hl, u8_t tc, u8_t nexth, struct netif *netif);
 #if LWIP_NETIF_HWADDRHINT
-err_t         ip6_output_hinted(struct pbuf *p, ip6_addr_t *src, ip6_addr_t *dest,
+err_t         ip6_output_hinted(struct pbuf *p, const ip6_addr_t *src, const ip6_addr_t *dest,
                                 u8_t hl, u8_t tc, u8_t nexth, u8_t *addr_hint);
 #endif /* LWIP_NETIF_HWADDRHINT */
 #if LWIP_IPV6_MLD
diff --git a/src/include/lwip/mld6.h b/src/include/lwip/mld6.h
index f629c3db..d5b515a0 100644
--- a/src/include/lwip/mld6.h
+++ b/src/include/lwip/mld6.h
@@ -103,10 +103,10 @@ PACK_STRUCT_END
 err_t  mld6_stop(struct netif *netif);
 void   mld6_report_groups(struct netif *netif);
 void   mld6_tmr(void);
-struct mld_group *mld6_lookfor_group(struct netif *ifp, ip6_addr_t *addr);
+struct mld_group *mld6_lookfor_group(struct netif *ifp, const ip6_addr_t *addr);
 void   mld6_input(struct pbuf *p, struct netif *inp);
-err_t  mld6_joingroup(ip6_addr_t *srcaddr, ip6_addr_t *groupaddr);
-err_t  mld6_leavegroup(ip6_addr_t *srcaddr, ip6_addr_t *groupaddr);
+err_t  mld6_joingroup(const ip6_addr_t *srcaddr, const ip6_addr_t *groupaddr);
+err_t  mld6_leavegroup(const ip6_addr_t *srcaddr, const ip6_addr_t *groupaddr);
 
 
 #ifdef __cplusplus
diff --git a/src/include/lwip/nd6.h b/src/include/lwip/nd6.h
index 2a8401fc..5872ecae 100644
--- a/src/include/lwip/nd6.h
+++ b/src/include/lwip/nd6.h
@@ -345,12 +345,12 @@ extern u32_t retrans_timer;
 #define nd6_init() /* TODO should we init tables? */
 void nd6_tmr(void);
 void nd6_input(struct pbuf *p, struct netif *inp);
-s8_t nd6_get_next_hop_entry(ip6_addr_t * ip6addr, struct netif * netif);
-s8_t nd6_select_router(ip6_addr_t * ip6addr, struct netif * netif);
-u16_t nd6_get_destination_mtu(ip6_addr_t * ip6addr, struct netif * netif);
+s8_t nd6_get_next_hop_entry(const ip6_addr_t * ip6addr, struct netif * netif);
+s8_t nd6_select_router(const ip6_addr_t * ip6addr, struct netif * netif);
+u16_t nd6_get_destination_mtu(const ip6_addr_t * ip6addr, struct netif * netif);
 err_t nd6_queue_packet(s8_t neighbor_index, struct pbuf * p);
 #if LWIP_ND6_TCP_REACHABILITY_HINTS
-void nd6_reachability_hint(ip6_addr_t * ip6addr);
+void nd6_reachability_hint(const ip6_addr_t * ip6addr);
 #endif /* LWIP_ND6_TCP_REACHABILITY_HINTS */
 
 #ifdef __cplusplus
diff --git a/src/include/lwip/netif.h b/src/include/lwip/netif.h
index 03a820e1..810ace43 100644
--- a/src/include/lwip/netif.h
+++ b/src/include/lwip/netif.h
@@ -134,7 +134,7 @@ typedef err_t (*netif_output_fn)(struct netif *netif, struct pbuf *p,
  * @param ipaddr The IPv6 address to which the packet shall be sent
  */
 typedef err_t (*netif_output_ip6_fn)(struct netif *netif, struct pbuf *p,
-       ip6_addr_t *ipaddr);
+       const ip6_addr_t *ipaddr);
 #endif /* LWIP_IPV6 */
 /** Function prototype for netif->linkoutput functions. Only used for ethernet
  * netifs. This function is called by ARP when a packet shall be sent.
@@ -151,7 +151,7 @@ typedef err_t (*netif_igmp_mac_filter_fn)(struct netif *netif,
 #if LWIP_IPV6 && LWIP_IPV6_MLD
 /** Function prototype for netif mld_mac_filter functions */
 typedef err_t (*netif_mld_mac_filter_fn)(struct netif *netif,
-       ip6_addr_t *group, u8_t action);
+       const ip6_addr_t *group, u8_t action);
 #endif /* LWIP_IPV6 && LWIP_IPV6_MLD */
 
 /** Generic data structure used for all lwIP network interfaces.
diff --git a/src/include/lwip/udp.h b/src/include/lwip/udp.h
index be9579e8..24f84f4a 100644
--- a/src/include/lwip/udp.h
+++ b/src/include/lwip/udp.h
@@ -123,7 +123,7 @@ struct udp_pcb {
 
 #if LWIP_IGMP
   /** outgoing network interface for multicast packets */
-  const ip_addr_t multicast_ip;
+  ip_addr_t multicast_ip;
 #endif /* LWIP_IGMP */
 
 #if LWIP_UDPLITE
diff --git a/src/netif/ppp/ppp.c b/src/netif/ppp/ppp.c
index 204abd8d..980c752c 100644
--- a/src/netif/ppp/ppp.c
+++ b/src/netif/ppp/ppp.c
@@ -180,9 +180,9 @@ const struct protent* const protocols[] = {
 /* Prototypes for procedures local to this file. */
 static void ppp_do_open(void *arg);
 static err_t ppp_netif_init_cb(struct netif *netif);
-static err_t ppp_netif_output_ip4(struct netif *netif, struct pbuf *pb, ip_addr_t *ipaddr);
+static err_t ppp_netif_output_ip4(struct netif *netif, struct pbuf *pb, const ip_addr_t *ipaddr);
 #if PPP_IPV6_SUPPORT
-static err_t ppp_netif_output_ip6(struct netif *netif, struct pbuf *pb, ip6_addr_t *ipaddr);
+static err_t ppp_netif_output_ip6(struct netif *netif, struct pbuf *pb, const ip6_addr_t *ipaddr);
 #endif /* PPP_IPV6_SUPPORT */
 
 /***********************************/
@@ -453,7 +453,7 @@ static err_t ppp_netif_init_cb(struct netif *netif) {
 /*
  * Send an IPv4 packet on the given connection.
  */
-static err_t ppp_netif_output_ip4(struct netif *netif, struct pbuf *pb, ip_addr_t *ipaddr) {
+static err_t ppp_netif_output_ip4(struct netif *netif, struct pbuf *pb, const ip_addr_t *ipaddr) {
 #if PPP_IPV4_SUPPORT
   ppp_pcb *pcb = (ppp_pcb*)netif->state;
   LWIP_UNUSED_ARG(ipaddr);
@@ -480,7 +480,7 @@ static err_t ppp_netif_output_ip4(struct netif *netif, struct pbuf *pb, ip_addr_
 /*
  * Send an IPv6 packet on the given connection.
  */
-static err_t ppp_netif_output_ip6(struct netif *netif, struct pbuf *pb, ip6_addr_t *ipaddr) {
+static err_t ppp_netif_output_ip6(struct netif *netif, struct pbuf *pb, const ip6_addr_t *ipaddr) {
   ppp_pcb *pcb = (ppp_pcb*)netif->state;
   LWIP_UNUSED_ARG(ipaddr);