kernel/git/stable/linux.git/include/net/ip.h, branch linux-3.15.y

ip: make IP identifiers less predictable

2014-08-14T01:51:48+00:00

[ Upstream commit 04ca6973f7c1a0d8537f2d9906a0cf8e69886d75 ] In "Counting Packets Sent Between Arbitrary Internet Hosts", Jeffrey and Jedidiah describe ways exploiting linux IP identifier generation to infer whether two machines are exchanging packets. With commit 73f156a6e8c1 ("inetpeer: get rid of ip_id_count"), we changed IP id generation, but this does not really prevent this side-channel technique. This patch adds a random amount of perturbation so that IP identifiers for a given destination [1] are no longer monotonically increasing after an idle period. Note that prandom_u32_max(1) returns 0, so if generator is used at most once per jiffy, this patch inserts no hole in the ID suite and do not increase collision probability. This is jiffies based, so in the worst case (HZ=1000), the id can rollover after ~65 seconds of idle time, which should be fine. We also change the hash used in __ip_select_ident() to not only hash on daddr, but also saddr and protocol, so that ICMP probes can not be used to infer information for other protocols. For IPv6, adds saddr into the hash as well, but not nexthdr. If I ping the patched target, we can see ID are now hard to predict. 21:57:11.008086 IP (...) A > target: ICMP echo request, seq 1, length 64 21:57:11.010752 IP (... id 2081 ...) target > A: ICMP echo reply, seq 1, length 64 21:57:12.013133 IP (...) A > target: ICMP echo request, seq 2, length 64 21:57:12.015737 IP (... id 3039 ...) target > A: ICMP echo reply, seq 2, length 64 21:57:13.016580 IP (...) A > target: ICMP echo request, seq 3, length 64 21:57:13.019251 IP (... id 3437 ...) target > A: ICMP echo reply, seq 3, length 64 [1] TCP sessions uses a per flow ID generator not changed by this patch. Signed-off-by: Eric Dumazet Reported-by: Jeffrey Knockel Reported-by: Jedidiah R. Crandall Cc: Willy Tarreau Cc: Hannes Frederic Sowa Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

inetpeer: get rid of ip_id_count

2014-08-14T01:51:48+00:00

[ Upstream commit 73f156a6e8c1074ac6327e0abd1169e95eb66463 ] Ideally, we would need to generate IP ID using a per destination IP generator. linux kernels used inet_peer cache for this purpose, but this had a huge cost on servers disabling MTU discovery. 1) each inet_peer struct consumes 192 bytes 2) inetpeer cache uses a binary tree of inet_peer structs, with a nominal size of ~66000 elements under load. 3) lookups in this tree are hitting a lot of cache lines, as tree depth is about 20. 4) If server deals with many tcp flows, we have a high probability of not finding the inet_peer, allocating a fresh one, inserting it in the tree with same initial ip_id_count, (cf secure_ip_id()) 5) We garbage collect inet_peer aggressively. IP ID generation do not have to be 'perfect' Goal is trying to avoid duplicates in a short period of time, so that reassembly units have a chance to complete reassembly of fragments belonging to one message before receiving other fragments with a recycled ID. We simply use an array of generators, and a Jenkin hash using the dst IP as a key. ipv6_select_ident() is put back into net/ipv6/ip6_output.c where it belongs (it is only used from this file) secure_ip_id() and secure_ipv6_id() no longer are needed. Rename ip_select_ident_more() to ip_select_ident_segs() to avoid unnecessary decrement/increment of the number of segments. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

ipv4: add a sock pointer to dst->output() path.

2014-04-15T17:47:15+00:00

In the dst->output() path for ipv4, the code assumes the skb it has to transmit is attached to an inet socket, specifically via ip_mc_output() : The sk_mc_loop() test triggers a WARN_ON() when the provider of the packet is an AF_PACKET socket. The dst->output() method gets an additional 'struct sock *sk' parameter. This needs a cascade of changes so that this parameter can be propagated from vxlan to final consumer. Fixes: 8f646c922d55 ("vxlan: keep original skb ownership") Reported-by: lucien xin Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

ipv4: add a sock pointer to ip_queue_xmit()

2014-04-15T16:58:34+00:00

ip_queue_xmit() assumes the skb it has to transmit is attached to an inet socket. Commit 31c70d5956fc ("l2tp: keep original skb ownership") changed l2tp to not change skb ownership and thus broke this assumption. One fix is to add a new 'struct sock *sk' parameter to ip_queue_xmit(), so that we do not assume skb->sk points to the socket used by l2tp tunnel. Fixes: 31c70d5956fc ("l2tp: keep original skb ownership") Reported-by: Zhan Jianyu Tested-by: Zhan Jianyu Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: Use NET_ADD_STATS instead of NET_ADD_STATS_BH in tcp_event_new_data_sent()

2014-03-06T20:19:43+00:00

Can be invoked from non-BH context. Based upon a patch by Eric Dumazet. Fixes: f19c29e3e391 ("tcp: snmp stats for Fast Open, SYN rtx, and data pkts") Reported-by: Sergey Senozhatsky Signed-off-by: David S. Miller

ipv4: yet another new IP_MTU_DISCOVER option IP_PMTUDISC_OMIT

2014-02-26T20:51:00+00:00

IP_PMTUDISC_INTERFACE has a design error: because it does not allow the generation of fragments if the interface mtu is exceeded, it is very hard to make use of this option in already deployed name server software for which I introduced this option. This patch adds yet another new IP_MTU_DISCOVER option to not honor any path mtu information and not accepting new icmp notifications destined for the socket this option is enabled on. But we allow outgoing fragmentation in case the packet size exceeds the outgoing interface mtu. As such this new option can be used as a drop-in replacement for IP_PMTUDISC_DONT, which is currently in use by most name server software making the adoption of this option very smooth and easy. The original advantage of IP_PMTUDISC_INTERFACE is still maintained: ignoring incoming path MTU updates and not honoring discovered path MTUs in the output path. Fixes: 482fc6094afad5 ("ipv4: introduce new IP_MTU_DISCOVER mode IP_PMTUDISC_INTERFACE") Cc: Florian Weimer Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller

ipv6: honor IPV6_PKTINFO with v4 mapped addresses on sendmsg

2014-02-19T21:28:42+00:00

In case we decide in udp6_sendmsg to send the packet down the ipv4 udp_sendmsg path because the destination is either of family AF_INET or the destination is an ipv4 mapped ipv6 address, we don't honor the maybe specified ipv4 mapped ipv6 address in IPV6_PKTINFO. We simply can check for this option in ip_cmsg_send because no calls to ipv6 module functions are needed to do so. Reported-by: Gert Doering Cc: Tore Anderson Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller

ipv6: make IPV6_RECVPKTINFO work for ipv4 datagrams

2014-01-20T03:53:18+00:00

We currently don't report IPV6_RECVPKTINFO in cmsg access ancillary data for IPv4 datagrams on IPv6 sockets. This patch splits the ip6_datagram_recv_ctl into two functions, one which handles both protocol families, AF_INET and AF_INET6, while the ip6_datagram_recv_specific_ctl only handles IPv6 cmsg data. ip6_datagram_recv_*_ctl never reported back any errors, so we can make them return void. Also provide a helper for protocols which don't offer dual personality to further use ip6_datagram_recv_ctl, which is exported to modules. I needed to shuffle the code for ping around a bit to make it easier to implement dual personality for ping ipv6 sockets in future. Reported-by: Gert Doering Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller

ipv4: register igmp_notifier even when !CONFIG_PROC_FS

2014-01-14T23:03:33+00:00

We still need this notifier even when we don't config PROC_FS. It should be rare to have a kernel without PROC_FS, so just for completeness. Cc: Stephen Hemminger Cc: David S. Miller Cc: Patrick McHardy Signed-off-by: Cong Wang Signed-off-by: David S. Miller

ipv4: introduce ip_dst_mtu_maybe_forward and protect forwarding path against pmtu spoofing

2014-01-13T19:22:54+00:00

While forwarding we should not use the protocol path mtu to calculate the mtu for a forwarded packet but instead use the interface mtu. We mark forwarded skbs in ip_forward with IPSKB_FORWARDED, which was introduced for multicast forwarding. But as it does not conflict with our usage in unicast code path it is perfect for reuse. I moved the functions ip_sk_accept_pmtu, ip_sk_use_pmtu and ip_skb_dst_mtu along with the new ip_dst_mtu_maybe_forward to net/ip.h to fix circular dependencies because of IPSKB_FORWARDED. Because someone might have written a software which does probe destinations manually and expects the kernel to honour those path mtus I introduced a new per-namespace "ip_forward_use_pmtu" knob so someone can disable this new behaviour. We also still use mtus which are locked on a route for forwarding. The reason for this change is, that path mtus information can be injected into the kernel via e.g. icmp_err protocol handler without verification of local sockets. As such, this could cause the IPv4 forwarding path to wrongfully emit fragmentation needed notifications or start to fragment packets along a path. Tunnel and ipsec output paths clear IPCB again, thus IPSKB_FORWARDED won't be set and further fragmentation logic will use the path mtu to determine the fragmentation size. They also recheck packet size with help of path mtu discovery and report appropriate errors. Cc: Eric Dumazet Cc: David Miller Cc: John Heffner Cc: Steffen Klassert Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller