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linux/include/net/route.h
Sabrina Dubroca d52e5a7e7c ipv4: lock mtu in fnhe when received PMTU < net.ipv4.route.min_pmtu 
Prior to the rework of PMTU information storage in commit
2c8cec5c10 ("ipv4: Cache learned PMTU information in inetpeer."),
when a PMTU event advertising a PMTU smaller than
net.ipv4.route.min_pmtu was received, we would disable setting the DF
flag on packets by locking the MTU metric, and set the PMTU to
net.ipv4.route.min_pmtu.

Since then, we don't disable DF, and set PMTU to
net.ipv4.route.min_pmtu, so the intermediate router that has this link
with a small MTU will have to drop the packets.

This patch reestablishes pre-2.6.39 behavior by splitting
rtable->rt_pmtu into a bitfield with rt_mtu_locked and rt_pmtu.
rt_mtu_locked indicates that we shouldn't set the DF bit on that path,
and is checked in ip_dont_fragment().

One possible workaround is to set net.ipv4.route.min_pmtu to a value low
enough to accommodate the lowest MTU encountered.

Fixes: 2c8cec5c10 ("ipv4: Cache learned PMTU information in inetpeer.")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-03-14 13:37:36 -04:00

353 lines
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C
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/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* Definitions for the IP router.
*
* Version: @(#)route.h 1.0.4 05/27/93
*
* Authors: Ross Biro
* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
* Fixes:
* Alan Cox : Reformatted. Added ip_rt_local()
* Alan Cox : Support for TCP parameters.
* Alexey Kuznetsov: Major changes for new routing code.
* Mike McLagan : Routing by source
* Robert Olsson : Added rt_cache statistics
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#ifndef _ROUTE_H
#define _ROUTE_H
#include <net/dst.h>
#include <net/inetpeer.h>
#include <net/flow.h>
#include <net/inet_sock.h>
#include <net/ip_fib.h>
#include <linux/in_route.h>
#include <linux/rtnetlink.h>
#include <linux/rcupdate.h>
#include <linux/route.h>
#include <linux/ip.h>
#include <linux/cache.h>
#include <linux/security.h>
/* IPv4 datagram length is stored into 16bit field (tot_len) */
#define IP_MAX_MTU 0xFFFFU
#define RTO_ONLINK 0x01
#define RT_CONN_FLAGS(sk) (RT_TOS(inet_sk(sk)->tos) | sock_flag(sk, SOCK_LOCALROUTE))
#define RT_CONN_FLAGS_TOS(sk,tos) (RT_TOS(tos) | sock_flag(sk, SOCK_LOCALROUTE))
struct fib_nh;
struct fib_info;
struct uncached_list;
struct rtable {
struct dst_entry dst;
int rt_genid;
unsigned int rt_flags;
__u16 rt_type;
__u8 rt_is_input;
__u8 rt_uses_gateway;
int rt_iif;
/* Info on neighbour */
__be32 rt_gateway;
/* Miscellaneous cached information */
u32 rt_mtu_locked:1,
rt_pmtu:31;
u32 rt_table_id;
struct list_head rt_uncached;
struct uncached_list *rt_uncached_list;
};
static inline bool rt_is_input_route(const struct rtable *rt)
{
return rt->rt_is_input != 0;
}
static inline bool rt_is_output_route(const struct rtable *rt)
{
return rt->rt_is_input == 0;
}
static inline __be32 rt_nexthop(const struct rtable *rt, __be32 daddr)
{
if (rt->rt_gateway)
return rt->rt_gateway;
return daddr;
}
struct ip_rt_acct {
__u32 o_bytes;
__u32 o_packets;
__u32 i_bytes;
__u32 i_packets;
};
struct rt_cache_stat {
unsigned int in_slow_tot;
unsigned int in_slow_mc;
unsigned int in_no_route;
unsigned int in_brd;
unsigned int in_martian_dst;
unsigned int in_martian_src;
unsigned int out_slow_tot;
unsigned int out_slow_mc;
};
extern struct ip_rt_acct __percpu *ip_rt_acct;
struct in_device;
int ip_rt_init(void);
void rt_cache_flush(struct net *net);
void rt_flush_dev(struct net_device *dev);
struct rtable *ip_route_output_key_hash(struct net *net, struct flowi4 *flp,
const struct sk_buff *skb);
struct rtable *ip_route_output_key_hash_rcu(struct net *net, struct flowi4 *flp,
struct fib_result *res,
const struct sk_buff *skb);
static inline struct rtable *__ip_route_output_key(struct net *net,
struct flowi4 *flp)
{
return ip_route_output_key_hash(net, flp, NULL);
}
struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,
const struct sock *sk);
struct dst_entry *ipv4_blackhole_route(struct net *net,
struct dst_entry *dst_orig);
static inline struct rtable *ip_route_output_key(struct net *net, struct flowi4 *flp)
{
return ip_route_output_flow(net, flp, NULL);
}
static inline struct rtable *ip_route_output(struct net *net, __be32 daddr,
__be32 saddr, u8 tos, int oif)
{
struct flowi4 fl4 = {
.flowi4_oif = oif,
.flowi4_tos = tos,
.daddr = daddr,
.saddr = saddr,
};
return ip_route_output_key(net, &fl4);
}
static inline struct rtable *ip_route_output_ports(struct net *net, struct flowi4 *fl4,
struct sock *sk,
__be32 daddr, __be32 saddr,
__be16 dport, __be16 sport,
__u8 proto, __u8 tos, int oif)
{
flowi4_init_output(fl4, oif, sk ? sk->sk_mark : 0, tos,
RT_SCOPE_UNIVERSE, proto,
sk ? inet_sk_flowi_flags(sk) : 0,
daddr, saddr, dport, sport, sock_net_uid(net, sk));
if (sk)
security_sk_classify_flow(sk, flowi4_to_flowi(fl4));
return ip_route_output_flow(net, fl4, sk);
}
static inline struct rtable *ip_route_output_gre(struct net *net, struct flowi4 *fl4,
__be32 daddr, __be32 saddr,
__be32 gre_key, __u8 tos, int oif)
{
memset(fl4, 0, sizeof(*fl4));
fl4->flowi4_oif = oif;
fl4->daddr = daddr;
fl4->saddr = saddr;
fl4->flowi4_tos = tos;
fl4->flowi4_proto = IPPROTO_GRE;
fl4->fl4_gre_key = gre_key;
return ip_route_output_key(net, fl4);
}
int ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
u8 tos, struct net_device *dev,
struct in_device *in_dev, u32 *itag);
int ip_route_input_noref(struct sk_buff *skb, __be32 dst, __be32 src,
u8 tos, struct net_device *devin);
int ip_route_input_rcu(struct sk_buff *skb, __be32 dst, __be32 src,
u8 tos, struct net_device *devin,
struct fib_result *res);
static inline int ip_route_input(struct sk_buff *skb, __be32 dst, __be32 src,
u8 tos, struct net_device *devin)
{
int err;
rcu_read_lock();
err = ip_route_input_noref(skb, dst, src, tos, devin);
if (!err) {
skb_dst_force(skb);
if (!skb_dst(skb))
err = -EINVAL;
}
rcu_read_unlock();
return err;
}
void ipv4_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu, int oif,
u32 mark, u8 protocol, int flow_flags);
void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu);
void ipv4_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark,
u8 protocol, int flow_flags);
void ipv4_sk_redirect(struct sk_buff *skb, struct sock *sk);
void ip_rt_send_redirect(struct sk_buff *skb);
unsigned int inet_addr_type(struct net *net, __be32 addr);
unsigned int inet_addr_type_table(struct net *net, __be32 addr, u32 tb_id);
unsigned int inet_dev_addr_type(struct net *net, const struct net_device *dev,
__be32 addr);
unsigned int inet_addr_type_dev_table(struct net *net,
const struct net_device *dev,
__be32 addr);
void ip_rt_multicast_event(struct in_device *);
int ip_rt_ioctl(struct net *, unsigned int cmd, struct rtentry *rt);
void ip_rt_get_source(u8 *src, struct sk_buff *skb, struct rtable *rt);
struct rtable *rt_dst_alloc(struct net_device *dev,
unsigned int flags, u16 type,
bool nopolicy, bool noxfrm, bool will_cache);
struct in_ifaddr;
void fib_add_ifaddr(struct in_ifaddr *);
void fib_del_ifaddr(struct in_ifaddr *, struct in_ifaddr *);
void rt_add_uncached_list(struct rtable *rt);
void rt_del_uncached_list(struct rtable *rt);
static inline void ip_rt_put(struct rtable *rt)
{
/* dst_release() accepts a NULL parameter.
* We rely on dst being first structure in struct rtable
*/
BUILD_BUG_ON(offsetof(struct rtable, dst) != 0);
dst_release(&rt->dst);
}
#define IPTOS_RT_MASK (IPTOS_TOS_MASK & ~3)
extern const __u8 ip_tos2prio[16];
static inline char rt_tos2priority(u8 tos)
{
return ip_tos2prio[IPTOS_TOS(tos)>>1];
}
/* ip_route_connect() and ip_route_newports() work in tandem whilst
* binding a socket for a new outgoing connection.
*
* In order to use IPSEC properly, we must, in the end, have a
* route that was looked up using all available keys including source
* and destination ports.
*
* However, if a source port needs to be allocated (the user specified
* a wildcard source port) we need to obtain addressing information
* in order to perform that allocation.
*
* So ip_route_connect() looks up a route using wildcarded source and
* destination ports in the key, simply so that we can get a pair of
* addresses to use for port allocation.
*
* Later, once the ports are allocated, ip_route_newports() will make
* another route lookup if needed to make sure we catch any IPSEC
* rules keyed on the port information.
*
* The callers allocate the flow key on their stack, and must pass in
* the same flowi4 object to both the ip_route_connect() and the
* ip_route_newports() calls.
*/
static inline void ip_route_connect_init(struct flowi4 *fl4, __be32 dst, __be32 src,
u32 tos, int oif, u8 protocol,
__be16 sport, __be16 dport,
struct sock *sk)
{
__u8 flow_flags = 0;
if (inet_sk(sk)->transparent)
flow_flags |= FLOWI_FLAG_ANYSRC;
flowi4_init_output(fl4, oif, sk->sk_mark, tos, RT_SCOPE_UNIVERSE,
protocol, flow_flags, dst, src, dport, sport,
sk->sk_uid);
}
static inline struct rtable *ip_route_connect(struct flowi4 *fl4,
__be32 dst, __be32 src, u32 tos,
int oif, u8 protocol,
__be16 sport, __be16 dport,
struct sock *sk)
{
struct net *net = sock_net(sk);
struct rtable *rt;
ip_route_connect_init(fl4, dst, src, tos, oif, protocol,
sport, dport, sk);
if (!dst || !src) {
rt = __ip_route_output_key(net, fl4);
if (IS_ERR(rt))
return rt;
ip_rt_put(rt);
flowi4_update_output(fl4, oif, tos, fl4->daddr, fl4->saddr);
}
security_sk_classify_flow(sk, flowi4_to_flowi(fl4));
return ip_route_output_flow(net, fl4, sk);
}
static inline struct rtable *ip_route_newports(struct flowi4 *fl4, struct rtable *rt,
__be16 orig_sport, __be16 orig_dport,
__be16 sport, __be16 dport,
struct sock *sk)
{
if (sport != orig_sport || dport != orig_dport) {
fl4->fl4_dport = dport;
fl4->fl4_sport = sport;
ip_rt_put(rt);
flowi4_update_output(fl4, sk->sk_bound_dev_if,
RT_CONN_FLAGS(sk), fl4->daddr,
fl4->saddr);
security_sk_classify_flow(sk, flowi4_to_flowi(fl4));
return ip_route_output_flow(sock_net(sk), fl4, sk);
}
return rt;
}
static inline int inet_iif(const struct sk_buff *skb)
{
struct rtable *rt = skb_rtable(skb);
if (rt && rt->rt_iif)
return rt->rt_iif;
return skb->skb_iif;
}
static inline int ip4_dst_hoplimit(const struct dst_entry *dst)
{
int hoplimit = dst_metric_raw(dst, RTAX_HOPLIMIT);
struct net *net = dev_net(dst->dev);
if (hoplimit == 0)
hoplimit = net->ipv4.sysctl_ip_default_ttl;
return hoplimit;
}
#endif /* _ROUTE_H */
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