Switch the entire IPv4 stack to keep the IP packet header

in network byte order. Any host byte order processing is
done in local variables and host byte order values are
never[1] written to a packet.

  After this change a packet processed by the stack isn't
modified at all[2] except for TTL.

  After this change a network stack hacker doesn't need to
scratch his head trying to figure out what is the byte order
at the given place in the stack.

[1] One exception still remains. The raw sockets convert host
byte order before pass a packet to an application. Probably
this would remain for ages for compatibility.

[2] The ip_input() still subtructs header len from ip->ip_len,
but this is planned to be fixed soon.

Reviewed by:	luigi, Maxim Dounin <mdounin mdounin.ru>
Tested by:	ray, Olivier Cochard-Labbe <olivier cochard.me>

1 files changed, 3 insertions, 5 deletions

diff --git a/sys/netinet/ip_gre.c b/sys/netinet/ip_gre.c
index d0274de..0735311 100644
--- a/sys/netinet/ip_gre.c
+++ b/sys/netinet/ip_gre.c
@@ -274,12 +274,10 @@ gre_mobile_input(struct mbuf *m, int hlen)
 
 	/*
 	 * On FreeBSD, rip_input() supplies us with ip->ip_len
-	 * already converted into host byteorder and also decreases
-	 * it by the lengh of IP header, however, ip_input() expects
-	 * that this field is in the original format (network byteorder
-	 * and full size of IP packet), so that adjust accordingly.
+	 * decreased by the lengh of IP header, however, ip_input()
+	 * expects it to be full size of IP packet, so adjust accordingly.
 	 */
-	ip->ip_len = htons(ip->ip_len + sizeof(struct ip) - msiz);
+	ip->ip_len = htons(ntohs(ip->ip_len) + sizeof(struct ip) - msiz);
 
 	ip->ip_sum = 0;
 	ip->ip_sum = in_cksum(m, (ip->ip_hl << 2));