kernel/net/ipv4/sysctl_net_ipv4.c, branch linux-5.1.y

tcp: add tcp_min_snd_mss sysctl

2019-06-17T17:50:37Z

commit 5f3e2bf008c2221478101ee72f5cb4654b9fc363 upstream. Some TCP peers announce a very small MSS option in their SYN and/or SYN/ACK messages. This forces the stack to send packets with a very high network/cpu overhead. Linux has enforced a minimal value of 48. Since this value includes the size of TCP options, and that the options can consume up to 40 bytes, this means that each segment can include only 8 bytes of payload. In some cases, it can be useful to increase the minimal value to a saner value. We still let the default to 48 (TCP_MIN_SND_MSS), for compatibility reasons. Note that TCP_MAXSEG socket option enforces a minimal value of (TCP_MIN_MSS). David Miller increased this minimal value in commit c39508d6f118 ("tcp: Make TCP_MAXSEG minimum more correct.") from 64 to 88. We might in the future merge TCP_MIN_SND_MSS and TCP_MIN_MSS. CVE-2019-11479 -- tcp mss hardcoded to 48 Signed-off-by: Eric Dumazet Suggested-by: Jonathan Looney Acked-by: Neal Cardwell Cc: Yuchung Cheng Cc: Tyler Hicks Cc: Bruce Curtis Cc: Jonathan Lemon Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

ipv4: set the tcp_min_rtt_wlen range from 0 to one day

2019-04-17T20:57:11Z

There is a UBSAN report as below: UBSAN: Undefined behaviour in net/ipv4/tcp_input.c:2877:56 signed integer overflow: 2147483647 * 1000 cannot be represented in type 'int' CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.1.0-rc4-00058-g582549e #1 Call Trace: dump_stack+0x8c/0xba ubsan_epilogue+0x11/0x60 handle_overflow+0x12d/0x170 ? ttwu_do_wakeup+0x21/0x320 __ubsan_handle_mul_overflow+0x12/0x20 tcp_ack_update_rtt+0x76c/0x780 tcp_clean_rtx_queue+0x499/0x14d0 tcp_ack+0x69e/0x1240 ? __wake_up_sync_key+0x2c/0x50 ? update_group_capacity+0x50/0x680 tcp_rcv_established+0x4e2/0xe10 tcp_v4_do_rcv+0x22b/0x420 tcp_v4_rcv+0xfe8/0x1190 ip_protocol_deliver_rcu+0x36/0x180 ip_local_deliver+0x15b/0x1a0 ip_rcv+0xac/0xd0 __netif_receive_skb_one_core+0x7f/0xb0 __netif_receive_skb+0x33/0xc0 netif_receive_skb_internal+0x84/0x1c0 napi_gro_receive+0x2a0/0x300 receive_buf+0x3d4/0x2350 ? detach_buf_split+0x159/0x390 virtnet_poll+0x198/0x840 ? reweight_entity+0x243/0x4b0 net_rx_action+0x25c/0x770 __do_softirq+0x19b/0x66d irq_exit+0x1eb/0x230 do_IRQ+0x7a/0x150 common_interrupt+0xf/0xf It can be reproduced by: echo 2147483647 > /proc/sys/net/ipv4/tcp_min_rtt_wlen Fixes: f672258391b42 ("tcp: track min RTT using windowed min-filter") Signed-off-by: ZhangXiaoxu Signed-off-by: David S. Miller

net: provide a sysctl raw_l3mdev_accept for raw socket lookup with VRFs

2018-11-08T00:12:38Z

Add a sysctl raw_l3mdev_accept to control raw socket lookup in a manner similar to use of tcp_l3mdev_accept for stream and of udp_l3mdev_accept for datagram sockets. Have this default to enabled for reasons of backwards compatibility. This is so as to specify the output device with cmsg and IP_PKTINFO, but using a socket not bound to the corresponding VRF. This allows e.g. older ping implementations to be run with specifying the device but without executing it in the VRF. If the option is disabled, packets received in a VRF context are only handled by a raw socket bound to the VRF, and correspondingly packets in the default VRF are only handled by a socket not bound to any VRF. Signed-off-by: Mike Manning Reviewed-by: David Ahern Tested-by: David Ahern Signed-off-by: David S. Miller

net-tcp: /proc/sys/net/ipv4/tcp_probe_interval is a u32 not int

2018-09-27T03:33:21Z

(fix documentation and sysctl access to treat it as such) Tested: # zcat /proc/config.gz | egrep ^CONFIG_HZ CONFIG_HZ_1000=y CONFIG_HZ=1000 # echo $[(1<<32)/1000 + 1] | tee /proc/sys/net/ipv4/tcp_probe_interval 4294968 tee: /proc/sys/net/ipv4/tcp_probe_interval: Invalid argument # echo $[(1<<32)/1000] | tee /proc/sys/net/ipv4/tcp_probe_interval 4294967 # echo 0 | tee /proc/sys/net/ipv4/tcp_probe_interval # echo -1 | tee /proc/sys/net/ipv4/tcp_probe_interval -1 tee: /proc/sys/net/ipv4/tcp_probe_interval: Invalid argument Signed-off-by: Maciej Żenczykowski Signed-off-by: David S. Miller

net: ipv4: Notify about changes to ip_forward_update_priority

2018-08-01T16:52:30Z

Drivers may make offloading decision based on whether ip_forward_update_priority is enabled or not. Therefore distribute netevent notifications to give them a chance to react to a change. Signed-off-by: Petr Machata Reviewed-by: Ido Schimmel Signed-off-by: David S. Miller

net: ipv4: Control SKB reprioritization after forwarding

2018-08-01T16:52:30Z

After IPv4 packets are forwarded, the priority of the corresponding SKB is updated according to the TOS field of IPv4 header. This overrides any prioritization done earlier by e.g. an skbedit action or ingress-qos-map defined at a vlan device. Such overriding may not always be desirable. Even if the packet ends up being routed, which implies this is an L3 network node, an administrator may wish to preserve whatever prioritization was done earlier on in the pipeline. Therefore introduce a sysctl that controls this behavior. Keep the default value at 1 to maintain backward-compatible behavior. Signed-off-by: Petr Machata Reviewed-by: Ido Schimmel Signed-off-by: David S. Miller

ipv4: Return EINVAL when ping_group_range sysctl doesn't map to user ns

2018-07-06T02:51:18Z

The low and high values of the net.ipv4.ping_group_range sysctl were being silently forced to the default disabled state when a write to the sysctl contained GIDs that didn't map to the associated user namespace. Confusingly, the sysctl's write operation would return success and then a subsequent read of the sysctl would indicate that the low and high values are the overflowgid. This patch changes the behavior by clearly returning an error when the sysctl write operation receives a GID range that doesn't map to the associated user namespace. In such a situation, the previous value of the sysctl is preserved and that range will be returned in a subsequent read of the sysctl. Signed-off-by: Tyler Hicks Signed-off-by: David S. Miller

tcp: fix Fast Open key endianness

2018-06-30T09:40:46Z

Fast Open key could be stored in different endian based on the CPU. Previously hosts in different endianness in a server farm using the same key config (sysctl value) would produce different cookies. This patch fixes it by always storing it as little endian to keep same API for LE hosts. Reported-by: Daniele Iamartino Signed-off-by: Yuchung Cheng Signed-off-by: Eric Dumazet Signed-off-by: Neal Cardwell Signed-off-by: David S. Miller

net-tcp: extend tcp_tw_reuse sysctl to enable loopback only optimization

2018-06-04T21:13:35Z

This changes the /proc/sys/net/ipv4/tcp_tw_reuse from a boolean to an integer. It now takes the values 0, 1 and 2, where 0 and 1 behave as before, while 2 enables timewait socket reuse only for sockets that we can prove are loopback connections: ie. bound to 'lo' interface or where one of source or destination IPs is 127.0.0.0/8, ::ffff:127.0.0.0/104 or ::1. This enables quicker reuse of ephemeral ports for loopback connections - where tcp_tw_reuse is 100% safe from a protocol perspective (this assumes no artificially induced packet loss on 'lo'). This also makes estblishing many loopback connections *much* faster (allocating ports out of the first half of the ephemeral port range is significantly faster, then allocating from the second half) Without this change in a 32K ephemeral port space my sample program (it just establishes and closes [::1]:ephemeral -> [::1]:server_port connections in a tight loop) fails after 32765 connections in 24 seconds. With it enabled 50000 connections only take 4.7 seconds. This is particularly problematic for IPv6 where we only have one local address and cannot play tricks with varying source IP from 127.0.0.0/8 pool. Signed-off-by: Maciej Żenczykowski Cc: Neal Cardwell Cc: Yuchung Cheng Cc: Wei Wang Change-Id: I0377961749979d0301b7b62871a32a4b34b654e1 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: add tcp_comp_sack_nr sysctl

2018-05-18T15:40:27Z

This per netns sysctl allows for TCP SACK compression fine-tuning. This limits number of SACK that can be compressed. Using 0 disables SACK compression. Signed-off-by: Eric Dumazet Acked-by: Neal Cardwell Signed-off-by: David S. Miller