From 49d16b23cd1e61c028ee088c5a64e9ac6a9c6147 Mon Sep 17 00:00:00 2001 From: Andy Zhou Date: Fri, 15 May 2015 14:15:37 -0700 Subject: [PATCH] bridge_netfilter: No ICMP packet on IPv4 fragmentation error When bridge netfilter re-fragments an IP packet for output, all packets that can not be re-fragmented to their original input size should be silently discarded. However, current bridge netfilter output path generates an ICMP packet with 'size exceeded MTU' message for such packets, this is a bug. This patch refactors the ip_fragment() API to allow two separate use cases. The bridge netfilter user case will not send ICMP, the routing output will, as before. Signed-off-by: Andy Zhou Acked-by: Florian Westphal Signed-off-by: David S. Miller --- include/net/ip.h | 4 ++-- net/bridge/br_netfilter.c | 21 ++++++++++++++++++++- net/ipv4/ip_output.c | 40 ++++++++++++++++++++++++++++------------ 3 files changed, 50 insertions(+), 15 deletions(-) diff --git a/include/net/ip.h b/include/net/ip.h index 43f6f39..cd7a6a4 100644 --- a/include/net/ip.h +++ b/include/net/ip.h @@ -108,8 +108,8 @@ int ip_local_deliver(struct sk_buff *skb); int ip_mr_input(struct sk_buff *skb); int ip_output(struct sock *sk, struct sk_buff *skb); int ip_mc_output(struct sock *sk, struct sk_buff *skb); -int ip_fragment(struct sock *sk, struct sk_buff *skb, - int (*output)(struct sock *, struct sk_buff *)); +int ip_do_fragment(struct sock *sk, struct sk_buff *skb, + int (*output)(struct sock *, struct sk_buff *)); int ip_do_nat(struct sk_buff *skb); void ip_send_check(struct iphdr *ip); int __ip_local_out(struct sk_buff *skb); diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c index 2b0e8bb..1d2eb32 100644 --- a/net/bridge/br_netfilter.c +++ b/net/bridge/br_netfilter.c @@ -853,6 +853,25 @@ static int br_nf_push_frag_xmit(struct sock *sk, struct sk_buff *skb) return br_dev_queue_push_xmit(sk, skb); } +static int br_nf_ip_fragment(struct sock *sk, struct sk_buff *skb, + int (*output)(struct sock *, struct sk_buff *)) +{ + unsigned int mtu = ip_skb_dst_mtu(skb); + struct iphdr *iph = ip_hdr(skb); + struct rtable *rt = skb_rtable(skb); + struct net_device *dev = rt->dst.dev; + + if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) || + (IPCB(skb)->frag_max_size && + IPCB(skb)->frag_max_size > mtu))) { + IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS); + kfree_skb(skb); + return -EMSGSIZE; + } + + return ip_do_fragment(sk, skb, output); +} + static int br_nf_dev_queue_xmit(struct sock *sk, struct sk_buff *skb) { int ret; @@ -886,7 +905,7 @@ static int br_nf_dev_queue_xmit(struct sock *sk, struct sk_buff *skb) skb_copy_from_linear_data_offset(skb, -data->size, data->mac, data->size); - ret = ip_fragment(sk, skb, br_nf_push_frag_xmit); + ret = br_nf_ip_fragment(sk, skb, br_nf_push_frag_xmit); } else { nf_bridge_info_free(skb); ret = br_dev_queue_push_xmit(sk, skb); diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 2acc5dc..8d91b922 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -83,6 +83,9 @@ int sysctl_ip_default_ttl __read_mostly = IPDEFTTL; EXPORT_SYMBOL(sysctl_ip_default_ttl); +static int ip_fragment(struct sock *sk, struct sk_buff *skb, + int (*output)(struct sock *, struct sk_buff *)); + /* Generate a checksum for an outgoing IP datagram. */ void ip_send_check(struct iphdr *iph) { @@ -478,6 +481,28 @@ static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from) skb_copy_secmark(to, from); } +static int ip_fragment(struct sock *sk, struct sk_buff *skb, + int (*output)(struct sock *, struct sk_buff *)) +{ + struct iphdr *iph = ip_hdr(skb); + unsigned int mtu = ip_skb_dst_mtu(skb); + + if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) || + (IPCB(skb)->frag_max_size && + IPCB(skb)->frag_max_size > mtu))) { + struct rtable *rt = skb_rtable(skb); + struct net_device *dev = rt->dst.dev; + + IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS); + icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, + htonl(mtu)); + kfree_skb(skb); + return -EMSGSIZE; + } + + return ip_do_fragment(sk, skb, output); +} + /* * This IP datagram is too large to be sent in one piece. Break it up into * smaller pieces (each of size equal to IP header plus @@ -485,8 +510,8 @@ static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from) * single device frame, and queue such a frame for sending. */ -int ip_fragment(struct sock *sk, struct sk_buff *skb, - int (*output)(struct sock *, struct sk_buff *)) +int ip_do_fragment(struct sock *sk, struct sk_buff *skb, + int (*output)(struct sock *, struct sk_buff *)) { struct iphdr *iph; int ptr; @@ -507,15 +532,6 @@ int ip_fragment(struct sock *sk, struct sk_buff *skb, iph = ip_hdr(skb); mtu = ip_skb_dst_mtu(skb); - if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) || - (IPCB(skb)->frag_max_size && - 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(mtu)); - kfree_skb(skb); - return -EMSGSIZE; - } /* * Setup starting values. @@ -751,7 +767,7 @@ fail: IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS); return err; } -EXPORT_SYMBOL(ip_fragment); +EXPORT_SYMBOL(ip_do_fragment); int ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb) -- 2.7.4