net: The world is not perfect patch.

  Unless there will be any objection here, I suggest consider the
following patch which simply removes the code for the
-DI_WISH_WORLD_WERE_PERFECT in the three methods which use it.

The compilation errors we get when using -DI_WISH_WORLD_WERE_PERFECT
show that this code was not built and not used for really a long time.
Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -313,9 +313,8 @@ static void ipgre_tunnel_uninit(struct net_device *dev)
 
 static void ipgre_err(struct sk_buff *skb, u32 info)
 {
-#ifndef I_WISH_WORLD_WERE_PERFECT
 
-/* It is not :-( All the routers (except for Linux) return only
+/* All the routers (except for Linux) return only
    8 bytes of packet payload. It means, that precise relaying of
    ICMP in the real Internet is absolutely infeasible.
 
@@ -398,149 +397,6 @@ static void ipgre_err(struct sk_buff *skb, u32 info)
 out:
 	read_unlock(&ipgre_lock);
 	return;
-#else
-	struct iphdr *iph = (struct iphdr*)dp;
-	struct iphdr *eiph;
-	__be16	     *p = (__be16*)(dp+(iph->ihl<<2));
-	const int type = icmp_hdr(skb)->type;
-	const int code = icmp_hdr(skb)->code;
-	int rel_type = 0;
-	int rel_code = 0;
-	__be32 rel_info = 0;
-	__u32 n = 0;
-	__be16 flags;
-	int grehlen = (iph->ihl<<2) + 4;
-	struct sk_buff *skb2;
-	struct flowi fl;
-	struct rtable *rt;
-
-	if (p[1] != htons(ETH_P_IP))
-		return;
-
-	flags = p[0];
-	if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
-		if (flags&(GRE_VERSION|GRE_ROUTING))
-			return;
-		if (flags&GRE_CSUM)
-			grehlen += 4;
-		if (flags&GRE_KEY)
-			grehlen += 4;
-		if (flags&GRE_SEQ)
-			grehlen += 4;
-	}
-	if (len < grehlen + sizeof(struct iphdr))
-		return;
-	eiph = (struct iphdr*)(dp + grehlen);
-
-	switch (type) {
-	default:
-		return;
-	case ICMP_PARAMETERPROB:
-		n = ntohl(icmp_hdr(skb)->un.gateway) >> 24;
-		if (n < (iph->ihl<<2))
-			return;
-
-		/* So... This guy found something strange INSIDE encapsulated
-		   packet. Well, he is fool, but what can we do ?
-		 */
-		rel_type = ICMP_PARAMETERPROB;
-		n -= grehlen;
-		rel_info = htonl(n << 24);
-		break;
-
-	case ICMP_DEST_UNREACH:
-		switch (code) {
-		case ICMP_SR_FAILED:
-		case ICMP_PORT_UNREACH:
-			/* Impossible event. */
-			return;
-		case ICMP_FRAG_NEEDED:
-			/* And it is the only really necessary thing :-) */
-			n = ntohs(icmp_hdr(skb)->un.frag.mtu);
-			if (n < grehlen+68)
-				return;
-			n -= grehlen;
-			/* BSD 4.2 MORE DOES NOT EXIST IN NATURE. */
-			if (n > ntohs(eiph->tot_len))
-				return;
-			rel_info = htonl(n);
-			break;
-		default:
-			/* All others are translated to HOST_UNREACH.
-			   rfc2003 contains "deep thoughts" about NET_UNREACH,
-			   I believe, it is just ether pollution. --ANK
-			 */
-			rel_type = ICMP_DEST_UNREACH;
-			rel_code = ICMP_HOST_UNREACH;
-			break;
-		}
-		break;
-	case ICMP_TIME_EXCEEDED:
-		if (code != ICMP_EXC_TTL)
-			return;
-		break;
-	}
-
-	/* Prepare fake skb to feed it to icmp_send */
-	skb2 = skb_clone(skb, GFP_ATOMIC);
-	if (skb2 == NULL)
-		return;
-	dst_release(skb2->dst);
-	skb2->dst = NULL;
-	skb_pull(skb2, skb->data - (u8*)eiph);
-	skb_reset_network_header(skb2);
-
-	/* Try to guess incoming interface */
-	memset(&fl, 0, sizeof(fl));
-	fl.fl4_dst = eiph->saddr;
-	fl.fl4_tos = RT_TOS(eiph->tos);
-	fl.proto = IPPROTO_GRE;
-	if (ip_route_output_key(dev_net(skb->dev), &rt, &fl)) {
-		kfree_skb(skb2);
-		return;
-	}
-	skb2->dev = rt->u.dst.dev;
-
-	/* route "incoming" packet */
-	if (rt->rt_flags&RTCF_LOCAL) {
-		ip_rt_put(rt);
-		rt = NULL;
-		fl.fl4_dst = eiph->daddr;
-		fl.fl4_src = eiph->saddr;
-		fl.fl4_tos = eiph->tos;
-		if (ip_route_output_key(dev_net(skb->dev), &rt, &fl) ||
-		    rt->u.dst.dev->type != ARPHRD_IPGRE) {
-			ip_rt_put(rt);
-			kfree_skb(skb2);
-			return;
-		}
-	} else {
-		ip_rt_put(rt);
-		if (ip_route_input(skb2, eiph->daddr, eiph->saddr, eiph->tos, skb2->dev) ||
-		    skb2->dst->dev->type != ARPHRD_IPGRE) {
-			kfree_skb(skb2);
-			return;
-		}
-	}
-
-	/* change mtu on this route */
-	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
-		if (n > dst_mtu(skb2->dst)) {
-			kfree_skb(skb2);
-			return;
-		}
-		skb2->dst->ops->update_pmtu(skb2->dst, n);
-	} else if (type == ICMP_TIME_EXCEEDED) {
-		struct ip_tunnel *t = netdev_priv(skb2->dev);
-		if (t->parms.iph.ttl) {
-			rel_type = ICMP_DEST_UNREACH;
-			rel_code = ICMP_HOST_UNREACH;
-		}
-	}
-
-	icmp_send(skb2, rel_type, rel_code, rel_info);
-	kfree_skb(skb2);
-#endif
 }
 
 static inline void ipgre_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)

net/ipv4/ipip.c

@@ -278,9 +278,8 @@ static void ipip_tunnel_uninit(struct net_device *dev)
 
 static int ipip_err(struct sk_buff *skb, u32 info)
 {
-#ifndef I_WISH_WORLD_WERE_PERFECT
 
-/* It is not :-( All the routers (except for Linux) return only
+/* All the routers (except for Linux) return only
    8 bytes of packet payload. It means, that precise relaying of
    ICMP in the real Internet is absolutely infeasible.
  */
@@ -337,133 +336,6 @@ static int ipip_err(struct sk_buff *skb, u32 info)
 out:
 	read_unlock(&ipip_lock);
 	return err;
-#else
-	struct iphdr *iph = (struct iphdr*)dp;
-	int hlen = iph->ihl<<2;
-	struct iphdr *eiph;
-	const int type = icmp_hdr(skb)->type;
-	const int code = icmp_hdr(skb)->code;
-	int rel_type = 0;
-	int rel_code = 0;
-	__be32 rel_info = 0;
-	__u32 n = 0;
-	struct sk_buff *skb2;
-	struct flowi fl;
-	struct rtable *rt;
-
-	if (len < hlen + sizeof(struct iphdr))
-		return 0;
-	eiph = (struct iphdr*)(dp + hlen);
-
-	switch (type) {
-	default:
-		return 0;
-	case ICMP_PARAMETERPROB:
-		n = ntohl(icmp_hdr(skb)->un.gateway) >> 24;
-		if (n < hlen)
-			return 0;
-
-		/* So... This guy found something strange INSIDE encapsulated
-		   packet. Well, he is fool, but what can we do ?
-		 */
-		rel_type = ICMP_PARAMETERPROB;
-		rel_info = htonl((n - hlen) << 24);
-		break;
-
-	case ICMP_DEST_UNREACH:
-		switch (code) {
-		case ICMP_SR_FAILED:
-		case ICMP_PORT_UNREACH:
-			/* Impossible event. */
-			return 0;
-		case ICMP_FRAG_NEEDED:
-			/* And it is the only really necessary thing :-) */
-			n = ntohs(icmp_hdr(skb)->un.frag.mtu);
-			if (n < hlen+68)
-				return 0;
-			n -= hlen;
-			/* BSD 4.2 MORE DOES NOT EXIST IN NATURE. */
-			if (n > ntohs(eiph->tot_len))
-				return 0;
-			rel_info = htonl(n);
-			break;
-		default:
-			/* All others are translated to HOST_UNREACH.
-			   rfc2003 contains "deep thoughts" about NET_UNREACH,
-			   I believe, it is just ether pollution. --ANK
-			 */
-			rel_type = ICMP_DEST_UNREACH;
-			rel_code = ICMP_HOST_UNREACH;
-			break;
-		}
-		break;
-	case ICMP_TIME_EXCEEDED:
-		if (code != ICMP_EXC_TTL)
-			return 0;
-		break;
-	}
-
-	/* Prepare fake skb to feed it to icmp_send */
-	skb2 = skb_clone(skb, GFP_ATOMIC);
-	if (skb2 == NULL)
-		return 0;
-	dst_release(skb2->dst);
-	skb2->dst = NULL;
-	skb_pull(skb2, skb->data - (u8*)eiph);
-	skb_reset_network_header(skb2);
-
-	/* Try to guess incoming interface */
-	memset(&fl, 0, sizeof(fl));
-	fl.fl4_daddr = eiph->saddr;
-	fl.fl4_tos = RT_TOS(eiph->tos);
-	fl.proto = IPPROTO_IPIP;
-	if (ip_route_output_key(dev_net(skb->dev), &rt, &key)) {
-		kfree_skb(skb2);
-		return 0;
-	}
-	skb2->dev = rt->u.dst.dev;
-
-	/* route "incoming" packet */
-	if (rt->rt_flags&RTCF_LOCAL) {
-		ip_rt_put(rt);
-		rt = NULL;
-		fl.fl4_daddr = eiph->daddr;
-		fl.fl4_src = eiph->saddr;
-		fl.fl4_tos = eiph->tos;
-		if (ip_route_output_key(dev_net(skb->dev), &rt, &fl) ||
-		    rt->u.dst.dev->type != ARPHRD_TUNNEL) {
-			ip_rt_put(rt);
-			kfree_skb(skb2);
-			return 0;
-		}
-	} else {
-		ip_rt_put(rt);
-		if (ip_route_input(skb2, eiph->daddr, eiph->saddr, eiph->tos, skb2->dev) ||
-		    skb2->dst->dev->type != ARPHRD_TUNNEL) {
-			kfree_skb(skb2);
-			return 0;
-		}
-	}
-
-	/* change mtu on this route */
-	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
-		if (n > dst_mtu(skb2->dst)) {
-			kfree_skb(skb2);
-			return 0;
-		}
-		skb2->dst->ops->update_pmtu(skb2->dst, n);
-	} else if (type == ICMP_TIME_EXCEEDED) {
-		struct ip_tunnel *t = netdev_priv(skb2->dev);
-		if (t->parms.iph.ttl) {
-			rel_type = ICMP_DEST_UNREACH;
-			rel_code = ICMP_HOST_UNREACH;
-		}
-	}
-
-	icmp_send(skb2, rel_type, rel_code, rel_info);
-	kfree_skb(skb2);
-	return 0;
-#endif
 }
 
 static inline void ipip_ecn_decapsulate(const struct iphdr *outer_iph,

net/ipv6/sit.c

@@ -403,9 +403,8 @@ static void ipip6_tunnel_uninit(struct net_device *dev)
 
 static int ipip6_err(struct sk_buff *skb, u32 info)
 {
-#ifndef I_WISH_WORLD_WERE_PERFECT
 
-/* It is not :-( All the routers (except for Linux) return only
+/* All the routers (except for Linux) return only
    8 bytes of packet payload. It means, that precise relaying of
    ICMP in the real Internet is absolutely infeasible.
  */
@@ -462,92 +461,6 @@ static int ipip6_err(struct sk_buff *skb, u32 info)
 out:
 	read_unlock(&ipip6_lock);
 	return err;
-#else
-	struct iphdr *iph = (struct iphdr*)dp;
-	int hlen = iph->ihl<<2;
-	struct ipv6hdr *iph6;
-	const int type = icmp_hdr(skb)->type;
-	const int code = icmp_hdr(skb)->code;
-	int rel_type = 0;
-	int rel_code = 0;
-	int rel_info = 0;
-	struct sk_buff *skb2;
-	struct rt6_info *rt6i;
-
-	if (len < hlen + sizeof(struct ipv6hdr))
-		return;
-	iph6 = (struct ipv6hdr*)(dp + hlen);
-
-	switch (type) {
-	default:
-		return;
-	case ICMP_PARAMETERPROB:
-		if (icmp_hdr(skb)->un.gateway < hlen)
-			return;
-
-		/* So... This guy found something strange INSIDE encapsulated
-		   packet. Well, he is fool, but what can we do ?
-		 */
-		rel_type = ICMPV6_PARAMPROB;
-		rel_info = icmp_hdr(skb)->un.gateway - hlen;
-		break;
-
-	case ICMP_DEST_UNREACH:
-		switch (code) {
-		case ICMP_SR_FAILED:
-		case ICMP_PORT_UNREACH:
-			/* Impossible event. */
-			return;
-		case ICMP_FRAG_NEEDED:
-			/* Too complicated case ... */
-			return;
-		default:
-			/* All others are translated to HOST_UNREACH.
-			   rfc2003 contains "deep thoughts" about NET_UNREACH,
-			   I believe, it is just ether pollution. --ANK
-			 */
-			rel_type = ICMPV6_DEST_UNREACH;
-			rel_code = ICMPV6_ADDR_UNREACH;
-			break;
-		}
-		break;
-	case ICMP_TIME_EXCEEDED:
-		if (code != ICMP_EXC_TTL)
-			return;
-		rel_type = ICMPV6_TIME_EXCEED;
-		rel_code = ICMPV6_EXC_HOPLIMIT;
-		break;
-	}
-
-	/* Prepare fake skb to feed it to icmpv6_send */
-	skb2 = skb_clone(skb, GFP_ATOMIC);
-	if (skb2 == NULL)
-		return 0;
-	dst_release(skb2->dst);
-	skb2->dst = NULL;
-	skb_pull(skb2, skb->data - (u8*)iph6);
-	skb_reset_network_header(skb2);
-
-	/* Try to guess incoming interface */
-	rt6i = rt6_lookup(dev_net(skb->dev), &iph6->saddr, NULL, NULL, 0);
-	if (rt6i && rt6i->rt6i_dev) {
-		skb2->dev = rt6i->rt6i_dev;
-
-		rt6i = rt6_lookup(dev_net(skb->dev),
-				&iph6->daddr, &iph6->saddr, NULL, 0);
-
-		if (rt6i && rt6i->rt6i_dev && rt6i->rt6i_dev->type == ARPHRD_SIT) {
-			struct ip_tunnel *t = netdev_priv(rt6i->rt6i_dev);
-			if (rel_type == ICMPV6_TIME_EXCEED && t->parms.iph.ttl) {
-				rel_type = ICMPV6_DEST_UNREACH;
-				rel_code = ICMPV6_ADDR_UNREACH;
-			}
-			icmpv6_send(skb2, rel_type, rel_code, rel_info, skb2->dev);
-		}
-	}
-	kfree_skb(skb2);
-	return 0;
-#endif
 }
 
 static inline void ipip6_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)