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, 11 insertions, 4 deletions

diff --git a/sys/netinet/raw_ip.c b/sys/netinet/raw_ip.c
index e48b666..291ef9a 100644
--- a/sys/netinet/raw_ip.c
+++ b/sys/netinet/raw_ip.c
@@ -292,7 +292,8 @@ rip_input(struct mbuf *m, int off)
 	 * not modify the packet except for some
 	 * byte order swaps.
 	 */
-	ip->ip_len += off;
+	ip->ip_len = ntohs(ip->ip_len) + off;
+	ip->ip_off = ntohs(ip->ip_off);
 
 	hash = INP_PCBHASH_RAW(proto, ip->ip_src.s_addr,
 	    ip->ip_dst.s_addr, V_ripcbinfo.ipi_hashmask);
@@ -449,11 +450,11 @@ rip_output(struct mbuf *m, struct socket *so, u_long dst)
 		ip = mtod(m, struct ip *);
 		ip->ip_tos = inp->inp_ip_tos;
 		if (inp->inp_flags & INP_DONTFRAG)
-			ip->ip_off = IP_DF;
+			ip->ip_off = htons(IP_DF);
 		else
-			ip->ip_off = 0;
+			ip->ip_off = htons(0);
 		ip->ip_p = inp->inp_ip_p;
-		ip->ip_len = m->m_pkthdr.len;
+		ip->ip_len = htons(m->m_pkthdr.len);
 		ip->ip_src = inp->inp_laddr;
 		if (jailed(inp->inp_cred)) {
 			/*
@@ -505,6 +506,12 @@ rip_output(struct mbuf *m, struct socket *so, u_long dst)
 			ip->ip_id = ip_newid();
 
 		/*
+		 * Applications on raw sockets expect host byte order.
+		 */
+		ip->ip_len = htons(ip->ip_len);
+		ip->ip_off = htons(ip->ip_off);
+
+		/*
 		 * XXX prevent ip_output from overwriting header fields.
 		 */
 		flags |= IP_RAWOUTPUT;