IPv4: splitted IPv4 header fields version/len and tos, made macros depend on BYTE_ORDER to prevent unnecessary calls to htons()

src/core/ipv4/ip4.c

@@ -705,9 +705,10 @@ err_t ip_output_if_opt(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
     chk_sum += ip4_addr_get_u32(&iphdr->dest) >> 16;
 #endif /* CHECKSUM_GEN_IP_INLINE */
 
-    IPH_VHLTOS_SET(iphdr, 4, ip_hlen / 4, tos);
+    IPH_VHL_SET(iphdr, 4, ip_hlen / 4);
+    IPH_TOS_SET(iphdr, tos);
 #if CHECKSUM_GEN_IP_INLINE
-    chk_sum += iphdr->_v_hl_tos;
+    chk_sum += LWIP_MAKE_U16(tos, iphdr->_v_hl);
 #endif /* CHECKSUM_GEN_IP_INLINE */
     IPH_LEN_SET(iphdr, htons(p->tot_len));
 #if CHECKSUM_GEN_IP_INLINE

src/include/ipv4/lwip/ip4.h

@@ -62,8 +62,10 @@ extern "C" {
 #endif
 PACK_STRUCT_BEGIN
 struct ip_hdr {
-  /* version / header length / type of service */
-  PACK_STRUCT_FIELD(u16_t _v_hl_tos);
+  /* version / header length */
+  PACK_STRUCT_FIELD(u8_t _v_hl);
+  /* type of service */
+  PACK_STRUCT_FIELD(u8_t _tos);
   /* total length */
   PACK_STRUCT_FIELD(u16_t _len);
   /* identification */
@@ -89,9 +91,14 @@ PACK_STRUCT_END
 #  include "arch/epstruct.h"
 #endif
 
-#define IPH_V(hdr)  (ntohs((hdr)->_v_hl_tos) >> 12)
-#define IPH_HL(hdr) ((ntohs((hdr)->_v_hl_tos) >> 8) & 0x0f)
-#define IPH_TOS(hdr) (ntohs((hdr)->_v_hl_tos) & 0xff)
+#if BYTE_ORDER == LITTLE_ENDIAN
+#define IPH_V(hdr)  ((hdr)->_v_hl >> 4)
+#define IPH_HL(hdr) ((hdr)->_v_hl & 0x0f)
+#else /* BYTE_ORDER == LITTLE_ENDIAN */
+#define IPH_V(hdr)  ((hdr)->_v_hl & 0x0f)
+#define IPH_HL(hdr) ((hdr)->_v_hl >> 4)
+#endif /* BYTE_ORDER == LITTLE_ENDIAN */
+#define IPH_TOS(hdr) ((hdr)->_tos)
 #define IPH_LEN(hdr) ((hdr)->_len)
 #define IPH_ID(hdr) ((hdr)->_id)
 #define IPH_OFFSET(hdr) ((hdr)->_offset)
@@ -99,7 +106,12 @@ PACK_STRUCT_END
 #define IPH_PROTO(hdr) ((hdr)->_proto)
 #define IPH_CHKSUM(hdr) ((hdr)->_chksum)
 
-#define IPH_VHLTOS_SET(hdr, v, hl, tos) (hdr)->_v_hl_tos = (htons(((v) << 12) | ((hl) << 8) | (tos)))
+#if BYTE_ORDER == LITTLE_ENDIAN
+#define IPH_VHL_SET(hdr, v, hl) (hdr)->_v_hl = (((v) << 4) | (hl))
+#else /* BYTE_ORDER == LITTLE_ENDIAN */
+#define IPH_VHL_SET(hdr, v, hl) (hdr)->_v_hl = ((v) | ((hl) << 4))
+#endif /* BYTE_ORDER == LITTLE_ENDIAN */
+#define IPH_TOS_SET(hdr, tos) (hdr)->_tos = (tos)
 #define IPH_LEN_SET(hdr, len) (hdr)->_len = (len)
 #define IPH_ID_SET(hdr, id) (hdr)->_id = (id)
 #define IPH_OFFSET_SET(hdr, off) (hdr)->_offset = (off)