diff --git a/src/include/ipv4/lwip/ip_addr.h b/src/include/ipv4/lwip/ip_addr.h
index 2819b152..d877ebeb 100644
--- a/src/include/ipv4/lwip/ip_addr.h
+++ b/src/include/ipv4/lwip/ip_addr.h
@@ -46,6 +46,10 @@ PACK_STRUCT_END
 #  include "arch/epstruct.h"
 #endif
 
+/*
+ * struct ipaddr2 is used in the definition of the ARP packet format in
+ * order to support compilers that don't have structure packing.
+ */
 #ifdef PACK_STRUCT_USE_INCLUDES
 #  include "arch/bpstruct.h"
 #endif
@@ -71,48 +75,50 @@ extern const struct ip_addr ip_addr_broadcast;
 /** IP_ADDR_ can be used as a fixed IP address
  *  for the wildcard and the broadcast address
  */
-#define IP_ADDR_ANY ((struct ip_addr *)&ip_addr_any)
-#define IP_ADDR_BROADCAST ((struct ip_addr *)&ip_addr_broadcast)
+#define IP_ADDR_ANY         ((struct ip_addr *)&ip_addr_any)
+#define IP_ADDR_BROADCAST   ((struct ip_addr *)&ip_addr_broadcast)
 
-#define INADDR_NONE    ((u32_t) 0xffffffff)  /* 255.255.255.255 */
-#define INADDR_LOOPBACK    ((u32_t) 0x7f000001)  /* 127.0.0.1 */
+#define INADDR_NONE         ((u32_t)0xffffffff)  /* 255.255.255.255 */
+#define INADDR_LOOPBACK     ((u32_t)0x7f000001)  /* 127.0.0.1 */
 
 /* Definitions of the bits in an Internet address integer.
 
    On subnets, host and network parts are found according to
    the subnet mask, not these masks.  */
 
-#define  IN_CLASSA(a)    ((((u32_t)(a)) & 0x80000000) == 0)
-#define  IN_CLASSA_NET    0xff000000
-#define  IN_CLASSA_NSHIFT  24
-#define  IN_CLASSA_HOST    (0xffffffff & ~IN_CLASSA_NET)
-#define  IN_CLASSA_MAX    128
+#define IN_CLASSA(a)        ((((u32_t)(a)) & 0x80000000) == 0)
+#define IN_CLASSA_NET       0xff000000
+#define IN_CLASSA_NSHIFT    24
+#define IN_CLASSA_HOST      (0xffffffff & ~IN_CLASSA_NET)
+#define IN_CLASSA_MAX       128
 
-#define  IN_CLASSB(a)    ((((u32_t)(a)) & 0xc0000000) == 0x80000000)
-#define  IN_CLASSB_NET    0xffff0000
-#define  IN_CLASSB_NSHIFT  16
-#define  IN_CLASSB_HOST    (0xffffffff & ~IN_CLASSB_NET)
-#define  IN_CLASSB_MAX    65536
+#define IN_CLASSB(a)        ((((u32_t)(a)) & 0xc0000000) == 0x80000000)
+#define IN_CLASSB_NET       0xffff0000
+#define IN_CLASSB_NSHIFT    16
+#define IN_CLASSB_HOST      (0xffffffff & ~IN_CLASSB_NET)
+#define IN_CLASSB_MAX       65536
 
-#define  IN_CLASSC(a)    ((((u32_t)(a)) & 0xe0000000) == 0xc0000000)
-#define  IN_CLASSC_NET    0xffffff00
-#define  IN_CLASSC_NSHIFT  8
-#define  IN_CLASSC_HOST    (0xffffffff & ~IN_CLASSC_NET)
+#define IN_CLASSC(a)        ((((u32_t)(a)) & 0xe0000000) == 0xc0000000)
+#define IN_CLASSC_NET       0xffffff00
+#define IN_CLASSC_NSHIFT    8
+#define IN_CLASSC_HOST      (0xffffffff & ~IN_CLASSC_NET)
 
 #define IN_CLASSD(a)        (((u32_t)(a) & 0xf0000000) == 0xe0000000)
-#define IN_CLASSD_NET       0xf0000000  /* These ones aren't really */
-#define IN_CLASSD_NSHIFT    28      /* net and host fields, but */
-#define IN_CLASSD_HOST      0x0fffffff  /* routing needn't know.    */
+#define IN_CLASSD_NET       0xf0000000          /* These ones aren't really */
+#define IN_CLASSD_NSHIFT    28                  /*   net and host fields, but */
+#define IN_CLASSD_HOST      0x0fffffff          /*   routing needn't know. */
 #define IN_MULTICAST(a)     IN_CLASSD(a)
 
 #define IN_EXPERIMENTAL(a)  (((u32_t)(a) & 0xf0000000) == 0xf0000000)
 #define IN_BADCLASS(a)      (((u32_t)(a) & 0xf0000000) == 0xf0000000)
 
-#define IN_LOOPBACKNET      127         /* official! */
+#define IN_LOOPBACKNET      127                 /* official! */
 
-
-#define IP4_ADDR(ipaddr, a,b,c,d) (ipaddr)->addr = htonl(((u32_t)(a & 0xff) << 24) | ((u32_t)(b & 0xff) << 16) | \
-                                                         ((u32_t)(c & 0xff) << 8) | (u32_t)(d & 0xff))
+#define IP4_ADDR(ipaddr, a,b,c,d) \
+        (ipaddr)->addr = htonl(((u32_t)((a) & 0xff) << 24) | \
+                               ((u32_t)((b) & 0xff) << 16) | \
+                               ((u32_t)((c) & 0xff) << 8) | \
+                                (u32_t)((d) & 0xff))
 
 #define ip_addr_set(dest, src) (dest)->addr = \
                                ((src) == NULL? 0:\
@@ -137,23 +143,18 @@ u8_t ip_addr_isbroadcast(struct ip_addr *, struct netif *);
 
 #define ip_addr_ismulticast(addr1) (((addr1)->addr & ntohl(0xf0000000)) == ntohl(0xe0000000))
 
+#define ip_addr_debug_print(debug, ipaddr) \
+        LWIP_DEBUGF(debug, ("%"U16_F".%"U16_F".%"U16_F".%"U16_F, \
+                ipaddr ? (u16_t)(ntohl((ipaddr)->addr) >> 24) & 0xff : 0, \
+                ipaddr ? (u16_t)(ntohl((ipaddr)->addr) >> 16) & 0xff : 0, \
+                ipaddr ? (u16_t)(ntohl((ipaddr)->addr) >> 8) & 0xff : 0, \
+                ipaddr ? (u16_t)ntohl((ipaddr)->addr) & 0xff : 0))
 
-#define ip_addr_debug_print(debug, ipaddr) LWIP_DEBUGF(debug, ("%"U16_F".%"U16_F".%"U16_F".%"U16_F, \
-        ipaddr?(u16_t)(ntohl((ipaddr)->addr) >> 24) & 0xff:0, \
-        ipaddr?(u16_t)(ntohl((ipaddr)->addr) >> 16) & 0xff:0, \
-        ipaddr?(u16_t)(ntohl((ipaddr)->addr) >> 8) & 0xff:0, \
-        ipaddr?(u16_t)ntohl((ipaddr)->addr) & 0xff:0U))
-
-/* cast to unsigned int, as it is used as argument to printf functions
- * which expect integer arguments. CSi: use cc.h formatters (conversion chars)! */
+/* These are cast to u16_t, with the intent that they are often arguments
+ * to printf using the U16_F format from cc.h. */
 #define ip4_addr1(ipaddr) ((u16_t)(ntohl((ipaddr)->addr) >> 24) & 0xff)
 #define ip4_addr2(ipaddr) ((u16_t)(ntohl((ipaddr)->addr) >> 16) & 0xff)
 #define ip4_addr3(ipaddr) ((u16_t)(ntohl((ipaddr)->addr) >> 8) & 0xff)
 #define ip4_addr4(ipaddr) ((u16_t)(ntohl((ipaddr)->addr)) & 0xff)
+
 #endif /* __LWIP_IP_ADDR_H__ */
-
-
-
-
-
-