diff options
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 13 | ||||
| -rw-r--r-- | include/net/ip.h | 33 | ||||
| -rw-r--r-- | include/net/netns/ipv4.h | 1 | ||||
| -rw-r--r-- | include/net/route.h | 19 | ||||
| -rw-r--r-- | net/ipv4/ip_forward.c | 7 | ||||
| -rw-r--r-- | net/ipv4/ip_output.c | 8 | ||||
| -rw-r--r-- | net/ipv4/route.c | 3 | ||||
| -rw-r--r-- | net/ipv4/sysctl_net_ipv4.c | 7 |
8 files changed, 67 insertions, 24 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 7373115407e4..0d71fa962d8a 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -32,6 +32,19 @@ ip_no_pmtu_disc - INTEGER min_pmtu - INTEGER default 552 - minimum discovered Path MTU +ip_forward_use_pmtu - BOOLEAN + By default we don't trust protocol path MTUs while forwarding + because they could be easily forged and can lead to unwanted + fragmentation by the router. + You only need to enable this if you have user-space software + which tries to discover path mtus by itself and depends on the + kernel honoring this information. This is normally not the + case. + Default: 0 (disabled) + Possible values: + 0 - disabled + 1 - enabled + route/max_size - INTEGER Maximum number of routes allowed in the kernel. Increase this when using large numbers of interfaces and/or routes. diff --git a/include/net/ip.h b/include/net/ip.h index 535664477c4a..0dab95c2e4d5 100644 --- a/include/net/ip.h +++ b/include/net/ip.h @@ -263,6 +263,39 @@ int ip_dont_fragment(struct sock *sk, struct dst_entry *dst) !(dst_metric_locked(dst, RTAX_MTU))); } +static inline bool ip_sk_accept_pmtu(const struct sock *sk) +{ + return inet_sk(sk)->pmtudisc != IP_PMTUDISC_INTERFACE; +} + +static inline bool ip_sk_use_pmtu(const struct sock *sk) +{ + return inet_sk(sk)->pmtudisc < IP_PMTUDISC_PROBE; +} + +static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst, + bool forwarding) +{ + struct net *net = dev_net(dst->dev); + + if (net->ipv4.sysctl_ip_fwd_use_pmtu || + dst_metric_locked(dst, RTAX_MTU) || + !forwarding) + return dst_mtu(dst); + + return min(dst->dev->mtu, IP_MAX_MTU); +} + +static inline unsigned int ip_skb_dst_mtu(const struct sk_buff *skb) +{ + if (!skb->sk || ip_sk_use_pmtu(skb->sk)) { + bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED; + return ip_dst_mtu_maybe_forward(skb_dst(skb), forwarding); + } else { + return min(skb_dst(skb)->dev->mtu, IP_MAX_MTU); + } +} + void __ip_select_ident(struct iphdr *iph, struct dst_entry *dst, int more); static inline void ip_select_ident(struct sk_buff *skb, struct dst_entry *dst, struct sock *sk) diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 929a668e91a9..80f500a29498 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -70,6 +70,7 @@ struct netns_ipv4 { int sysctl_tcp_ecn; int sysctl_ip_no_pmtu_disc; + int sysctl_ip_fwd_use_pmtu; kgid_t sysctl_ping_group_range[2]; diff --git a/include/net/route.h b/include/net/route.h index 638e3ebf76f3..9d1f423d5944 100644 --- a/include/net/route.h +++ b/include/net/route.h @@ -36,6 +36,9 @@ #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)) @@ -311,20 +314,4 @@ static inline int ip4_dst_hoplimit(const struct dst_entry *dst) return hoplimit; } -static inline bool ip_sk_accept_pmtu(const struct sock *sk) -{ - return inet_sk(sk)->pmtudisc != IP_PMTUDISC_INTERFACE; -} - -static inline bool ip_sk_use_pmtu(const struct sock *sk) -{ - return inet_sk(sk)->pmtudisc < IP_PMTUDISC_PROBE; -} - -static inline int ip_skb_dst_mtu(const struct sk_buff *skb) -{ - return (!skb->sk || ip_sk_use_pmtu(skb->sk)) ? - dst_mtu(skb_dst(skb)) : skb_dst(skb)->dev->mtu; -} - #endif /* _ROUTE_H */ diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c index 694de3b7aebf..e9f1217a8afd 100644 --- a/net/ipv4/ip_forward.c +++ b/net/ipv4/ip_forward.c @@ -54,6 +54,7 @@ static int ip_forward_finish(struct sk_buff *skb) int ip_forward(struct sk_buff *skb) { + u32 mtu; struct iphdr *iph; /* Our header */ struct rtable *rt; /* Route we use */ struct ip_options *opt = &(IPCB(skb)->opt); @@ -88,11 +89,13 @@ int ip_forward(struct sk_buff *skb) if (opt->is_strictroute && rt->rt_uses_gateway) goto sr_failed; - if (unlikely(skb->len > dst_mtu(&rt->dst) && !skb_is_gso(skb) && + IPCB(skb)->flags |= IPSKB_FORWARDED; + mtu = ip_dst_mtu_maybe_forward(&rt->dst, true); + if (unlikely(skb->len > mtu && !skb_is_gso(skb) && (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) { IP_INC_STATS(dev_net(rt->dst.dev), IPSTATS_MIB_FRAGFAILS); icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, - htonl(dst_mtu(&rt->dst))); + htonl(mtu)); goto drop; } diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index df184616493f..9a78804cfe9c 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -449,6 +449,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) __be16 not_last_frag; struct rtable *rt = skb_rtable(skb); int err = 0; + bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED; dev = rt->dst.dev; @@ -458,12 +459,13 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) iph = ip_hdr(skb); + mtu = ip_dst_mtu_maybe_forward(&rt->dst, forwarding); if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) || (IPCB(skb)->frag_max_size && - IPCB(skb)->frag_max_size > dst_mtu(&rt->dst)))) { + IPCB(skb)->frag_max_size > mtu))) { IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS); icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, - htonl(ip_skb_dst_mtu(skb))); + htonl(mtu)); kfree_skb(skb); return -EMSGSIZE; } @@ -473,7 +475,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) */ hlen = iph->ihl * 4; - mtu = dst_mtu(&rt->dst) - hlen; /* Size of data space */ + mtu = mtu - hlen; /* Size of data space */ #ifdef CONFIG_BRIDGE_NETFILTER if (skb->nf_bridge) mtu -= nf_bridge_mtu_reduction(skb); diff --git a/net/ipv4/route.c b/net/ipv4/route.c index f8da28278014..25071b48921c 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -112,9 +112,6 @@ #define RT_FL_TOS(oldflp4) \ ((oldflp4)->flowi4_tos & (IPTOS_RT_MASK | RTO_ONLINK)) -/* IPv4 datagram length is stored into 16bit field (tot_len) */ -#define IP_MAX_MTU 0xFFFF - #define RT_GC_TIMEOUT (300*HZ) static int ip_rt_max_size; diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 1d2480ac2bb6..44eba052b43d 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -831,6 +831,13 @@ static struct ctl_table ipv4_net_table[] = { .mode = 0644, .proc_handler = proc_dointvec }, + { + .procname = "ip_forward_use_pmtu", + .data = &init_net.ipv4.sysctl_ip_fwd_use_pmtu, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, { } }; |