From 4adf0af6818f3ea52421dc0bae836cfaf20ef72a Mon Sep 17 00:00:00 2001 From: Simon Wunderlich Date: Wed, 30 Jul 2008 16:27:55 -0700 Subject: [PATCH] bridge: send correct MTU value in PMTU (revised) When bridging interfaces with different MTUs, the bridge correctly chooses the minimum of the MTUs of the physical devices as the bridges MTU. But when a frame is passed which fits through the incoming, but not through the outgoing interface, a "Fragmentation Needed" packet is generated. However, the propagated MTU is hardcoded to 1500, which is wrong in this situation. The sender will repeat the packet again with the same frame size, and the same problem will occur again. Instead of sending 1500, the (correct) MTU value of the bridge is now sent via PMTU. To achieve this, the corresponding rtable structure is stored in its net_bridge structure. Modified to get rid of fake_net_device as well. Signed-off-by: Simon Wunderlich Signed-off-by: Stephen Hemminger Signed-off-by: David S. Miller --- net/bridge/br_device.c | 9 +++++- net/bridge/br_if.c | 3 ++ net/bridge/br_netfilter.c | 63 +++++++++++++++++++++------------------ net/bridge/br_private.h | 6 ++++ 4 files changed, 51 insertions(+), 30 deletions(-) diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c index d9449df7cad5..9b58d70b0e7d 100644 --- a/net/bridge/br_device.c +++ b/net/bridge/br_device.c @@ -68,10 +68,17 @@ static int br_dev_stop(struct net_device *dev) static int br_change_mtu(struct net_device *dev, int new_mtu) { - if (new_mtu < 68 || new_mtu > br_min_mtu(netdev_priv(dev))) + struct net_bridge *br = netdev_priv(dev); + if (new_mtu < 68 || new_mtu > br_min_mtu(br)) return -EINVAL; dev->mtu = new_mtu; + +#ifdef CONFIG_BRIDGE_NETFILTER + /* remember the MTU in the rtable for PMTU */ + br->fake_rtable.u.dst.metrics[RTAX_MTU - 1] = new_mtu; +#endif + return 0; } diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c index a072ea5ca6f5..63c18aacde8c 100644 --- a/net/bridge/br_if.c +++ b/net/bridge/br_if.c @@ -202,6 +202,9 @@ static struct net_device *new_bridge_dev(const char *name) br->topology_change = 0; br->topology_change_detected = 0; br->ageing_time = 300 * HZ; + + br_netfilter_rtable_init(br); + INIT_LIST_HEAD(&br->age_list); br_stp_timer_init(br); diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c index bb90cd7bace3..6e280a8a31ee 100644 --- a/net/bridge/br_netfilter.c +++ b/net/bridge/br_netfilter.c @@ -101,33 +101,30 @@ static inline __be16 pppoe_proto(const struct sk_buff *skb) pppoe_proto(skb) == htons(PPP_IPV6) && \ brnf_filter_pppoe_tagged) -/* We need these fake structures to make netfilter happy -- - * lots of places assume that skb->dst != NULL, which isn't - * all that unreasonable. - * +/* + * Initialize bogus route table used to keep netfilter happy. * Currently, we fill in the PMTU entry because netfilter * refragmentation needs it, and the rt_flags entry because * ipt_REJECT needs it. Future netfilter modules might - * require us to fill additional fields. */ -static struct net_device __fake_net_device = { - .hard_header_len = ETH_HLEN, -#ifdef CONFIG_NET_NS - .nd_net = &init_net, -#endif -}; + * require us to fill additional fields. + */ +void br_netfilter_rtable_init(struct net_bridge *br) +{ + struct rtable *rt = &br->fake_rtable; -static struct rtable __fake_rtable = { - .u = { - .dst = { - .__refcnt = ATOMIC_INIT(1), - .dev = &__fake_net_device, - .path = &__fake_rtable.u.dst, - .metrics = {[RTAX_MTU - 1] = 1500}, - .flags = DST_NOXFRM, - } - }, - .rt_flags = 0, -}; + atomic_set(&rt->u.dst.__refcnt, 1); + rt->u.dst.dev = &br->dev; + rt->u.dst.path = &rt->u.dst; + rt->u.dst.metrics[RTAX_MTU - 1] = 1500; + rt->u.dst.flags = DST_NOXFRM; +} + +static inline struct rtable *bridge_parent_rtable(const struct net_device *dev) +{ + struct net_bridge_port *port = rcu_dereference(dev->br_port); + + return port ? &port->br->fake_rtable : NULL; +} static inline struct net_device *bridge_parent(const struct net_device *dev) { @@ -226,8 +223,12 @@ static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb) } nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING; - skb->rtable = &__fake_rtable; - dst_hold(&__fake_rtable.u.dst); + skb->rtable = bridge_parent_rtable(nf_bridge->physindev); + if (!skb->rtable) { + kfree_skb(skb); + return 0; + } + dst_hold(&skb->rtable->u.dst); skb->dev = nf_bridge->physindev; nf_bridge_push_encap_header(skb); @@ -391,8 +392,12 @@ bridged_dnat: skb->pkt_type = PACKET_HOST; } } else { - skb->rtable = &__fake_rtable; - dst_hold(&__fake_rtable.u.dst); + skb->rtable = bridge_parent_rtable(nf_bridge->physindev); + if (!skb->rtable) { + kfree_skb(skb); + return 0; + } + dst_hold(&skb->rtable->u.dst); } skb->dev = nf_bridge->physindev; @@ -611,8 +616,8 @@ static unsigned int br_nf_local_in(unsigned int hook, struct sk_buff *skb, const struct net_device *out, int (*okfn)(struct sk_buff *)) { - if (skb->rtable == &__fake_rtable) { - dst_release(&__fake_rtable.u.dst); + if (skb->rtable && skb->rtable == bridge_parent_rtable(in)) { + dst_release(&skb->rtable->u.dst); skb->rtable = NULL; } diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h index 815ed38925b2..c3dc18ddc043 100644 --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -15,6 +15,7 @@ #include #include +#include #define BR_HASH_BITS 8 #define BR_HASH_SIZE (1 << BR_HASH_BITS) @@ -92,6 +93,9 @@ struct net_bridge struct hlist_head hash[BR_HASH_SIZE]; struct list_head age_list; unsigned long feature_mask; +#ifdef CONFIG_BRIDGE_NETFILTER + struct rtable fake_rtable; +#endif unsigned long flags; #define BR_SET_MAC_ADDR 0x00000001 @@ -197,9 +201,11 @@ extern int br_ioctl_deviceless_stub(struct net *net, unsigned int cmd, void __us #ifdef CONFIG_BRIDGE_NETFILTER extern int br_netfilter_init(void); extern void br_netfilter_fini(void); +extern void br_netfilter_rtable_init(struct net_bridge *); #else #define br_netfilter_init() (0) #define br_netfilter_fini() do { } while(0) +#define br_netfilter_rtable_init(x) #endif /* br_stp.c */ -- 2.20.1