kernel/linux.git/include/net/netns/ipv6.h, branch linux-7.1.y

ipv6: flowlabel: enforce per-netns limit for unprivileged callers

2026-05-08T21:59:14+00:00

fl_size, fl_ht and ip6_fl_lock in net/ipv6/ip6_flowlabel.c are file scope and shared across netns. mem_check() reads fl_size to decide whether to deny non-CAP_NET_ADMIN callers. capable() runs against init_user_ns, so an unprivileged user in any non-init userns can push fl_size past FL_MAX_SIZE - FL_MAX_SIZE / 4 and starve every other unprivileged userns on the host. Add struct netns_ipv6::flowlabel_count, bumped and decremented next to fl_size in fl_intern, ip6_fl_gc and ip6_fl_purge. The new field fills the existing 4-byte hole after ipmr_seq, so struct netns_ipv6 stays the same size on 64-bit builds. Bump FL_MAX_SIZE from 4096 to 8192. It has been 4096 since the file was added. Machines and connection counts have grown. mem_check() folds an extra per-netns ceiling into the existing non-CAP_NET_ADMIN conditional. The ceiling is half of the total budget that unprivileged callers have ever been able to use, i.e. (FL_MAX_SIZE - FL_MAX_SIZE / 4) / 2 = 3072 entries. With FL_MAX_SIZE doubled, this preserves the original per-user reach of 3K (what an unprivileged caller could already obtain before this change), while forcing an attacker to spread allocations across at least two netns to exhaust the global non-CAP_NET_ADMIN budget. CAP_NET_ADMIN against init_user_ns still bypasses both caps. The previous patch took ip6_fl_lock across mem_check and fl_intern, so the new flowlabel_count read in mem_check and the new flowlabel_count++ in fl_intern run under the same critical section. flowlabel_count is therefore plain int, like fl_size. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Suggested-by: Willem de Bruijn Reviewed-by: Willem de Bruijn Cc: stable@vger.kernel.org # v5.15+ Signed-off-by: Maoyi Xie Link: https://patch.msgid.link/20260506082416.2259567-3-maoyixie.tju@gmail.com Signed-off-by: Jakub Kicinski

ipmr/ip6mr: Convert net->ipv[46].ipmr_seq to atomic_t.

2026-03-03T02:49:41+00:00

We will no longer hold RTNL for ipmr_mfc_add() and ipmr_mfc_delete(). MFC entry can be loosely connected with VIF by its index for mrt->vif_table[] (stored in mfc_parent), but the two tables are not synchronised. i.e. Even if VIF 1 is removed, MFC for VIF 1 is not automatically removed. The only field that the MFC/VIF interfaces share is net->ipv[46].ipmr_seq, which is protected by RTNL. Adding a new mutex for both just to protect a single field is overkill. Let's convert the field to atomic_t. Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260228221800.1082070-14-kuniyu@google.com Signed-off-by: Jakub Kicinski

ipv6: add sysctl_ipv6_flowlabel group

2026-01-19T17:56:42+00:00

Group together following struct netns_sysctl_ipv6 fields: - flowlabel_consistency - auto_flowlabels - flowlabel_state_ranges After this patch, ip6_make_flowlabel() uses a single cache line to fetch auto_flowlabels and flowlabel_state_ranges (instead of two before the patch). Signed-off-by: Eric Dumazet Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260115094141.3124990-2-edumazet@google.com Signed-off-by: Jakub Kicinski

ipv6: icmp: Add RFC 5837 support

2025-10-30T01:28:30+00:00

Add the ability to append the incoming IP interface information to ICMPv6 error messages in accordance with RFC 5837 and RFC 4884. This is required for more meaningful traceroute results in unnumbered networks. The feature is disabled by default and controlled via a new sysctl ("net.ipv6.icmp.errors_extension_mask") which accepts a bitmask of ICMP extensions to append to ICMP error messages. Currently, only a single value is supported, but the interface and the implementation should be able to support more extensions, if needed. Clone the skb and copy the relevant data portions before modifying the skb as the caller of icmp6_send() still owns the skb after the function returns. This should be fine since by default ICMP error messages are rate limited to 1000 per second and no more than 1 per second per specific host. Trim or pad the packet to 128 bytes before appending the ICMP extension structure in order to be compatible with legacy applications that assume that the ICMP extension structure always starts at this offset (the minimum length specified by RFC 4884). Since commit 20e1954fe238 ("ipv6: RFC 4884 partial support for SIT/GRE tunnels") it is possible for icmp6_send() to be called with an skb that already contains ICMP extensions. This can happen when we receive an ICMPv4 message with extensions from a tunnel and translate it to an ICMPv6 message towards an IPv6 host in the overlay network. I could not find an RFC that supports this behavior, but it makes sense to not overwrite the original extensions that were appended to the packet. Therefore, avoid appending extensions if the length field in the provided ICMPv6 header is already filled. Export netdev_copy_name() using EXPORT_IPV6_MOD_GPL() to make it available to IPv6 when it is built as a module. Reviewed-by: Petr Machata Reviewed-by: David Ahern Reviewed-by: Willem de Bruijn Signed-off-by: Ido Schimmel Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20251027082232.232571-3-idosch@nvidia.com Signed-off-by: Jakub Kicinski

ipv6: Protect fib6_link_table() with spinlock.

2025-04-24T07:29:56+00:00

We will get rid of RTNL from RTM_NEWROUTE and SIOCADDRT. If the request specifies a new table ID, fib6_new_table() is called to create a new routing table. Two concurrent requests could specify the same table ID, so we need a lock to protect net->ipv6.fib_table_hash[h]. Let's add a spinlock to protect the hash bucket linkage. Signed-off-by: Kuniyuki Iwashima Acked-by: Paolo Abeni Link: https://patch.msgid.link/20250418000443.43734-13-kuniyu@amazon.com Signed-off-by: Paolo Abeni

net/ipv6: convert skip_notify_on_dev_down sysctl to u8

2023-06-03T05:55:43+00:00

Save a bit a space, and could help future sysctls to use the same pattern. Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Acked-by: Matthieu Baerts Signed-off-by: Jakub Kicinski

net/ipv6: fix bool/int mismatch for skip_notify_on_dev_down

2023-06-03T05:55:43+00:00

skip_notify_on_dev_down ctl table expects this field to be an int (4 bytes), not a bool (1 byte). Because proc_dou8vec_minmax() was added in 5.13, this patch converts skip_notify_on_dev_down to an int. Following patch then converts the field to u8 and use proc_dou8vec_minmax(). Fixes: 7c6bb7d2faaf ("net/ipv6: Add knob to skip DELROUTE message on device down") Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Acked-by: Matthieu Baerts Signed-off-by: Jakub Kicinski

ipv6: add icmpv6_error_anycast_as_unicast for ICMPv6

2023-04-21T03:07:50+00:00

ICMPv6 error packets are not sent to the anycast destinations and this prevents things like traceroute from working. So create a setting similar to ECHO when dealing with Anycast sources (icmpv6_echo_ignore_anycast). Signed-off-by: Mahesh Bandewar Reviewed-by: David Ahern Reviewed-by: Maciej Żenczykowski Link: https://lore.kernel.org/r/20230419013238.2691167-1-maheshb@google.com Signed-off-by: Jakub Kicinski

ipv6: make ip6_rt_gc_expire an atomic_t

2022-04-15T21:28:50+00:00

Reads and Writes to ip6_rt_gc_expire always have been racy, as syzbot reported lately [1] There is a possible risk of under-flow, leading to unexpected high value passed to fib6_run_gc(), although I have not observed this in the field. Hosts hitting ip6_dst_gc() very hard are under pretty bad state anyway. [1] BUG: KCSAN: data-race in ip6_dst_gc / ip6_dst_gc read-write to 0xffff888102110744 of 4 bytes by task 13165 on cpu 1: ip6_dst_gc+0x1f3/0x220 net/ipv6/route.c:3311 dst_alloc+0x9b/0x160 net/core/dst.c:86 ip6_dst_alloc net/ipv6/route.c:344 [inline] icmp6_dst_alloc+0xb2/0x360 net/ipv6/route.c:3261 mld_sendpack+0x2b9/0x580 net/ipv6/mcast.c:1807 mld_send_cr net/ipv6/mcast.c:2119 [inline] mld_ifc_work+0x576/0x800 net/ipv6/mcast.c:2651 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289 worker_thread+0x618/0xa70 kernel/workqueue.c:2436 kthread+0x1a9/0x1e0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 read-write to 0xffff888102110744 of 4 bytes by task 11607 on cpu 0: ip6_dst_gc+0x1f3/0x220 net/ipv6/route.c:3311 dst_alloc+0x9b/0x160 net/core/dst.c:86 ip6_dst_alloc net/ipv6/route.c:344 [inline] icmp6_dst_alloc+0xb2/0x360 net/ipv6/route.c:3261 mld_sendpack+0x2b9/0x580 net/ipv6/mcast.c:1807 mld_send_cr net/ipv6/mcast.c:2119 [inline] mld_ifc_work+0x576/0x800 net/ipv6/mcast.c:2651 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289 worker_thread+0x618/0xa70 kernel/workqueue.c:2436 kthread+0x1a9/0x1e0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 value changed: 0x00000bb3 -> 0x00000ba9 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 11607 Comm: kworker/0:21 Not tainted 5.18.0-rc1-syzkaller-00037-g42e7a03d3bad-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: mld mld_ifc_work Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet Reported-by: syzbot Reviewed-by: David Ahern Link: https://lore.kernel.org/r/20220413181333.649424-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2022-02-17T19:44:20+00:00

No conflicts. Signed-off-by: Jakub Kicinski