Avoid using read/modify/write cycles to

set frag_off field of IPv4 header in hot paths.
Use __constant_htons as appropriate.

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index b5d4485d08f2256849b533d6e3e7e510e39f77ba..3d4c5c7ea3912efddc7bae27f7dd80c3efaa33ed 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -135,9 +135,10 @@ int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
        iph->version  = 4;
        iph->ihl      = 5;
        iph->tos      = inet->tos;
-       iph->frag_off = 0;
        if (ip_dont_fragment(sk, &rt->u.dst))
-               iph->frag_off |= htons(IP_DF);
+               iph->frag_off = __constant_htons(IP_DF);
+       else
+               iph->frag_off = 0;
        iph->ttl      = inet->ttl;
        iph->daddr    = rt->rt_dst;
        iph->saddr    = rt->rt_src;
@@ -308,9 +309,6 @@ static inline int ip_queue_xmit2(struct sk_buff *skb)
        if (skb->len > rt->u.dst.pmtu)
                goto fragment;
 
-       if (ip_dont_fragment(sk, &rt->u.dst))
-               iph->frag_off |= __constant_htons(IP_DF);
-
        ip_select_ident(iph, &rt->u.dst, sk);
 
        /* Add an IP checksum. */
@@ -324,7 +322,6 @@ fragment:
                /* Reject packet ONLY if TCP might fragment
                 * it itself, if were careful enough.
                 */
-               iph->frag_off |= __constant_htons(IP_DF);
                NETDEBUG(printk(KERN_DEBUG "sending pkt_too_big to self\n"));
 
                icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
@@ -385,7 +382,10 @@ packet_routed:
        iph = (struct iphdr *) skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
        *((__u16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
        iph->tot_len = htons(skb->len);
-       iph->frag_off = 0;
+       if (ip_dont_fragment(sk, &rt->u.dst))
+               iph->frag_off = __constant_htons(IP_DF);
+       else
+               iph->frag_off = 0;
        iph->ttl      = inet->ttl;
        iph->protocol = sk->protocol;
        iph->saddr    = rt->rt_src;
@@ -452,7 +452,7 @@ static int ip_build_xmit_slow(struct sock *sk,
 
        mtu = rt->u.dst.pmtu;
        if (ip_dont_fragment(sk, &rt->u.dst))
-               df = htons(IP_DF);
+               df = __constant_htons(IP_DF);
 
        length -= sizeof(struct iphdr);
 
@@ -573,7 +573,7 @@ static int ip_build_xmit_slow(struct sock *sk,
                                /*
                                 *      Any further fragments will have MF set.
                                 */
-                               mf = htons(IP_MF);
+                               mf = __constant_htons(IP_MF);
                        }
                        if (rt->rt_type == RTN_MULTICAST)
                                iph->ttl = inet->mc_ttl;
@@ -672,7 +672,7 @@ int ip_build_xmit(struct sock *sk,
         */
        df = 0;
        if (ip_dont_fragment(sk, &rt->u.dst))
-               df = htons(IP_DF);
+               df = __constant_htons(IP_DF);
 
        /* 
         *      Fast path for unfragmented frames without options. 
@@ -776,7 +776,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
         */
 
        offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
-       not_last_frag = iph->frag_off & htons(IP_MF);
+       not_last_frag = iph->frag_off & __constant_htons(IP_MF);
 
        /*
         *      Keep copying data until we run out.
@@ -861,7 +861,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
                 *                 last fragment then keep MF on each bit
                 */
                if (left > 0 || not_last_frag)
-                       iph->frag_off |= htons(IP_MF);
+                       iph->frag_off |= __constant_htons(IP_MF);
                ptr += len;
                offset += len;