ipv4: Kill ip_rt_frag_needed().

There is zero point to this function.

It's only real substance is to perform an extremely outdated BSD4.2
ICMP check, which we can safely remove.  If you really have a MTU
limited link being routed by a BSD4.2 derived system, here's a nickel
go buy yourself a real router.

The other actions of ip_rt_frag_needed(), checking and conditionally
updating the peer, are done by the per-protocol handlers of the ICMP
event.

TCP, UDP, et al. have a handler which will receive this event and
transmit it back into the associated route via dst_ops->update_pmtu().

This simplification is important, because it eliminates the one place
where we do not have a proper route context in which to make an
inetpeer lookup.

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 1 insertions, 70 deletions

diff --git a/include/net/route.h b/include/net/route.h
index 6340c37677fc..cc693a5bb20d 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -215,8 +215,6 @@ static inline int ip_route_input_noref(struct sk_buff *skb, __be32 dst, __be32 s
         return ip_route_input_common(skb, dst, src, tos, devin, true);
 }
 
-extern unsigned short   ip_rt_frag_needed(struct net *net, const struct iphdr *iph,
-                                          unsigned short new_mtu, struct net_device *dev);
 extern void             ip_rt_send_redirect(struct sk_buff *skb);
 
 extern unsigned int             inet_addr_type(struct net *net, __be32 addr);
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 0c78ef1e5dde..e1caa1abe5d1 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -673,9 +673,7 @@ static void icmp_unreach(struct sk_buff *skb)
                                 LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"),
                                                &iph->daddr);
                         } else {
-                                info = ip_rt_frag_needed(net, iph,
-                                                         ntohs(icmph->un.frag.mtu),
-                                                         skb->dev);
+                                info = ntohs(icmph->un.frag.mtu);
                                 if (!info)
                                         goto out;
                         }
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 03e5b614370e..4f5834c4a667 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1664,67 +1664,6 @@ out:	kfree_skb(skb);
         return 0;
 }
 
-/*
- *      The last two values are not from the RFC but
- *      are needed for AMPRnet AX.25 paths.
- */
-
-static const unsigned short mtu_plateau[] =
-{32000, 17914, 8166, 4352, 2002, 1492, 576, 296, 216, 128 };
-
-static inline unsigned short guess_mtu(unsigned short old_mtu)
-{
-        int i;
-
-        for (i = 0; i < ARRAY_SIZE(mtu_plateau); i++)
-                if (old_mtu > mtu_plateau[i])
-                        return mtu_plateau[i];
-        return 68;
-}
-
-unsigned short ip_rt_frag_needed(struct net *net, const struct iphdr *iph,
-                                 unsigned short new_mtu,
-                                 struct net_device *dev)
-{
-        unsigned short old_mtu = ntohs(iph->tot_len);
-        unsigned short est_mtu = 0;
-        struct inet_peer *peer;
-
-        peer = inet_getpeer_v4(net->ipv4.peers, iph->daddr, 1);
-        if (peer) {
-                unsigned short mtu = new_mtu;
-
-                if (new_mtu < 68 || new_mtu >= old_mtu) {
-                        /* BSD 4.2 derived systems incorrectly adjust
-                         * tot_len by the IP header length, and report
-                         * a zero MTU in the ICMP message.
-                         */
-                        if (mtu == 0 &&
-                            old_mtu >= 68 + (iph->ihl << 2))
-                                old_mtu -= iph->ihl << 2;
-                        mtu = guess_mtu(old_mtu);
-                }
-
-                if (mtu < ip_rt_min_pmtu)
-                        mtu = ip_rt_min_pmtu;
-                if (!peer->pmtu_expires || mtu < peer->pmtu_learned) {
-                        unsigned long pmtu_expires;
-
-                        pmtu_expires = jiffies + ip_rt_mtu_expires;
-                        if (!pmtu_expires)
-                                pmtu_expires = 1UL;
-
-                        est_mtu = mtu;
-                        peer->pmtu_learned = mtu;
-                        peer->pmtu_expires = pmtu_expires;
-                        atomic_inc(&__rt_peer_genid);
-                }
-
-                inet_putpeer(peer);
-        }
-        return est_mtu ? : new_mtu;
-}
-
 static void check_peer_pmtu(struct dst_entry *dst, struct inet_peer *peer)
 {
         unsigned long expires = ACCESS_ONCE(peer->pmtu_expires);
diff --git a/net/rxrpc/ar-error.c b/net/rxrpc/ar-error.c
index 5d6b572a6704..a9206087b4d7 100644
--- a/net/rxrpc/ar-error.c
+++ b/net/rxrpc/ar-error.c
@@ -81,10 +81,6 @@ void rxrpc_UDP_error_report(struct sock *sk)
                         _net("I/F MTU %u", mtu);
                 }
 
-                /* ip_rt_frag_needed() may have eaten the info */
-                if (mtu == 0)
-                        mtu = ntohs(icmp_hdr(skb)->un.frag.mtu);
-
                 if (mtu == 0) {
                         /* they didn't give us a size, estimate one */
                         if (mtu > 1500) {