linux/include/net/ip.h

512 lines
14 KiB

ipv4: introduce ip_dst_mtu_maybe_forward and protect forwarding path against pmtu spoofing 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 <eric.dumazet@gmail.com> Cc: David Miller <davem@davemloft.net> Cc: John Heffner <johnwheffner@gmail.com> Cc: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-01-09 10:01:15 +01:00
ip: make IP identifiers less predictable [ 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 <edumazet@google.com> Reported-by: Jeffrey Knockel <jeffk@cs.unm.edu> Reported-by: Jedidiah R. Crandall <crandall@cs.unm.edu> Cc: Willy Tarreau <w@1wt.eu> Cc: Hannes Frederic Sowa <hannes@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-07-26 08:58:10 +02:00
inetpeer: get rid of ip_id_count [ 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 <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-06-02 05:26:03 -07:00
inetpeer: get rid of ip_id_count [ 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 <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-06-02 05:26:03 -07:00
inetpeer: get rid of ip_id_count [ 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 <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-06-02 05:26:03 -07:00