Make lwIP compile with clang -Wdocumentation -> several documentation fixes

src/core/ipv4/etharp.c

@@ -72,6 +72,7 @@
  */
 #define ARP_MAXPENDING 5
 
+/** ARP states */
 enum etharp_state {
   ETHARP_STATE_EMPTY = 0,
   ETHARP_STATE_PENDING,
@@ -239,7 +240,7 @@ etharp_tmr(void)
  * old entries. Heuristic choose the least important entry for recycling.
  *
  * @param ipaddr IP address to find in ARP cache, or to add if not found.
- * @param flags @see definition of ETHARP_FLAG_*
+ * @param flags See @ref etharp_state
  * @param netif netif related to this address (used for NETIF_HWADDRHINT)
  *
  * @return The ARP entry index that matched or is created, ERR_MEM if no
@@ -402,7 +403,7 @@ etharp_find_entry(const ip4_addr_t *ipaddr, u8_t flags, struct netif* netif)
  * @param netif netif related to this entry (used for NETIF_ADDRHINT)
  * @param ipaddr IP address of the inserted ARP entry.
  * @param ethaddr Ethernet address of the inserted ARP entry.
- * @param flags @see definition of ETHARP_FLAG_*
+ * @param flags See @ref etharp_state
  *
  * @return
  * - ERR_OK Successfully updated ARP cache.
@@ -626,8 +627,6 @@ etharp_get_entry(u8_t i, ip4_addr_t **ipaddr, struct netif **netif, struct eth_a
  * @param p The ARP packet that arrived on netif. Is freed by this function.
  * @param netif The lwIP network interface on which the ARP packet pbuf arrived.
  *
- * @return NULL
- *
  * @see pbuf_free()
  */
 void

src/core/ipv4/igmp.c

@@ -723,8 +723,6 @@ igmp_delaying_member(struct igmp_group *group, u8_t maxresp)
  * @param src the source IP address to send from (if src == IP4_ADDR_ANY, the
  *         IP  address of the netif used to send is used as source address)
  * @param dest the destination IP address to send the packet to
- * @param ttl the TTL value to be set in the IP header
- * @param proto the PROTOCOL to be set in the IP header
  * @param netif the netif on which to send this packet
  * @return ERR_OK if the packet was sent OK
  *         ERR_BUF if p doesn't have enough space for IP/LINK headers

src/core/ipv4/ip4.c

@@ -222,7 +222,6 @@ ip4_route(const ip4_addr_t *dest)
  * that may not be forwarded, or whether datagrams to that destination
  * may be forwarded.
  * @param p the packet to forward
- * @param dest the destination IP address
  * @return 1: can forward 0: discard
  */
 static int

src/core/ipv4/ip4_frag.c

@@ -331,7 +331,7 @@ ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev)
  * will grow over time as  new pbufs are rx.
  * Also checks that the datagram passes basic continuity checks (if the last
  * fragment was received at least once).
- * @param root_p points to the 'root' pbuf for the current datagram being assembled.
+ * @param ipr points to the reassembly state
  * @param new_p points to the pbuf for the current fragment
  * @return 0 if invalid, >0 otherwise
  */