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c2a936600f
Increase the amount of memory usage limits for incomplete IP fragments. Arguing for new thresh high/low values: High threshold = 4 MBytes Low threshold = 3 MBytes The fragmentation memory accounting code, tries to account for the real memory usage, by measuring both the size of frag queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue)) and the SKB's truesize. We want to be able to handle/hold-on-to enough fragments, to ensure good performance, without causing incomplete fragments to hurt scalability, by causing the number of inet_frag_queue to grow too much (resulting longer searches for frag queues). For IPv4, how much memory does the largest frag consume. Maximum size fragment is 64K, which is approx 44 fragments with MTU(1500) sized packets. Sizeof(struct ipq) is 200. A 1500 byte packet results in a truesize of 2944 (not 2048 as I first assumed) (44*2944)+200 = 129736 bytes The current default high thresh of 262144 bytes, is obviously problematic, as only two 64K fragments can fit in the queue at the same time. How many 64K fragment can we fit into 4 MBytes: 4*2^20/((44*2944)+200) = 32.34 fragment in queues An attacker could send a separate/distinct fake fragment packets per queue, causing us to allocate one inet_frag_queue per packet, and thus attacking the hash table and its lists. How many frag queue do we need to store, and given a current hash size of 64, what is the average list length. Using one MTU sized fragment per inet_frag_queue, each consuming (2944+200) 3144 bytes. 4*2^20/(2944+200) = 1334 frag queues -> 21 avg list length An attack could send small fragments, the smallest packet I could send resulted in a truesize of 896 bytes (I'm a little surprised by this). 4*2^20/(896+200) = 3827 frag queues -> 59 avg list length When increasing these number, we also need to followup with improvements, that is going to help scalability. Simply increasing the hash size, is not enough as the current implementation does not have a per hash bucket locking. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| .. | ||
| netfilter | ||
| af_inet.c | ||
| ah4.c | ||
| arp.c | ||
| cipso_ipv4.c | ||
| datagram.c | ||
| devinet.c | ||
| esp4.c | ||
| fib_frontend.c | ||
| fib_lookup.h | ||
| fib_rules.c | ||
| fib_semantics.c | ||
| fib_trie.c | ||
| gre.c | ||
| icmp.c | ||
| igmp.c | ||
| inet_connection_sock.c | ||
| inet_diag.c | ||
| inet_fragment.c | ||
| inet_hashtables.c | ||
| inet_lro.c | ||
| inet_timewait_sock.c | ||
| inetpeer.c | ||
| ip_forward.c | ||
| ip_fragment.c | ||
| ip_gre.c | ||
| ip_input.c | ||
| ip_options.c | ||
| ip_output.c | ||
| ip_sockglue.c | ||
| ip_vti.c | ||
| ipcomp.c | ||
| ipconfig.c | ||
| ipip.c | ||
| ipmr.c | ||
| Kconfig | ||
| Makefile | ||
| netfilter.c | ||
| ping.c | ||
| proc.c | ||
| protocol.c | ||
| raw.c | ||
| route.c | ||
| syncookies.c | ||
| sysctl_net_ipv4.c | ||
| tcp.c | ||
| tcp_bic.c | ||
| tcp_cong.c | ||
| tcp_cubic.c | ||
| tcp_diag.c | ||
| tcp_fastopen.c | ||
| tcp_highspeed.c | ||
| tcp_htcp.c | ||
| tcp_hybla.c | ||
| tcp_illinois.c | ||
| tcp_input.c | ||
| tcp_ipv4.c | ||
| tcp_lp.c | ||
| tcp_memcontrol.c | ||
| tcp_metrics.c | ||
| tcp_minisocks.c | ||
| tcp_output.c | ||
| tcp_probe.c | ||
| tcp_scalable.c | ||
| tcp_timer.c | ||
| tcp_vegas.c | ||
| tcp_vegas.h | ||
| tcp_veno.c | ||
| tcp_westwood.c | ||
| tcp_yeah.c | ||
| tunnel4.c | ||
| udp.c | ||
| udp_diag.c | ||
| udp_impl.h | ||
| udplite.c | ||
| xfrm4_input.c | ||
| xfrm4_mode_beet.c | ||
| xfrm4_mode_transport.c | ||
| xfrm4_mode_tunnel.c | ||
| xfrm4_output.c | ||
| xfrm4_policy.c | ||
| xfrm4_state.c | ||
| xfrm4_tunnel.c | ||