[PATCH net v2 4/5] ipv4: restrict igmp_qrv to 255
flat view
WARM2d
REVIEWED: 1 (0M)
From: Jiayuan Chen <jiayuan.chen@linux.dev>
Date: 2026-10-27 10:49:28
Also in:
linux-doc, lkml, stable
Subsystem:
documentation, networking [general], the rest · Maintainers:
Jonathan Corbet, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Status: Reviewed.
Revision v2 (2 revisions archived); 1 review trailer.
Revisions (2)
- v1
- v2 current [diff against previous]
net.ipv4.igmp_qrv only has a lower bound, but ip_mc_reset() stores it
into the u8 in_device::mr_qrv, and the IGMPv3 retransmit counters filled
from it (crcount, sf_crcount) are u8 as well. Anything above 255
silently wraps. With 256, mr_qrv becomes 0, every
"in_dev->mr_qrv ?: sysctl_igmp_qrv" falls back to 256, which truncates
to 0 again in crcount, and igmpv3_send_cr() never puts the state change
records for the group into a report. The older version querier present
timeout (mr_qrv * mr_qi + mr_qri) also collapses to just mr_qri.
Make the sysctl a u8 like mr_qrv and switch to proc_dou8vec_minmax(),
which rejects anything above 255, and document it.
Fixes: a9fe8e29945d ("ipv4: implement igmp_qrv sysctl to tune igmp robustness variable")
Cc: <redacted>
Reviewed-by: Fernando Fernandez Mancera <redacted>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
For AI review: drivers/net/amt.c writing sysctl_igmp_qrv into the 3-bit
qrv wire fields is pre-existing and out of scope for this patch.
v2: switched to u8 and proc_dou8vec_minmax(), as suggested by Kuniyuki
Iwashima.
---
Documentation/networking/ip-sysctl.rst | 2 ++
Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst | 2 +-
include/net/netns/ipv4.h | 2 +-
net/ipv4/sysctl_net_ipv4.c | 4 ++--
4 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 71f334f27004e..9e282fb046904 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst@@ -1906,6 +1906,8 @@ igmp_qrv - INTEGER Minimum: 1 (as specified by RFC6636 4.5) + Maximum: 255 + force_igmp_version - INTEGER - 0 - (default) No enforcement of a IGMP version, IGMPv1/v2 fallback allowed. Will back to IGMPv3 mode again if all IGMPv1/v2 Querier
diff --git a/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst b/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst
index 3dc03bff739e4..2833ce6cba1d4 100644
--- a/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst
+++ b/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst@@ -143,9 +143,9 @@ int sysctl_udp_rmem_min u8 sysctl_fib_notify_on_flag_change u8 sysctl_udp_l3mdev_accept u8 sysctl_igmp_llm_reports +u8 sysctl_igmp_qrv int sysctl_igmp_max_memberships int sysctl_igmp_max_msf -int sysctl_igmp_qrv struct_ping_group_range ping_group_range atomic_t dev_addr_genid unsigned_int sysctl_udp_child_hash_entries
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index cb7f8bf15671c..3efbc7f4b4f7d 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h@@ -258,9 +258,9 @@ struct netns_ipv4 { #endif u8 sysctl_igmp_llm_reports; + u8 sysctl_igmp_qrv; int sysctl_igmp_max_memberships; int sysctl_igmp_max_msf; - int sysctl_igmp_qrv; struct ping_group_range ping_group_range; u16 ping_port_rover;
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index e3760daa34706..09f7fc6771456 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c@@ -975,9 +975,9 @@ static const struct ctl_table ipv4_net_table[] = { { .procname = "igmp_qrv", .data = &init_net.ipv4.sysctl_igmp_qrv, - .maxlen = sizeof(int), + .maxlen = sizeof(u8), .mode = 0644, - .proc_handler = proc_dointvec_minmax, + .proc_handler = proc_dou8vec_minmax, .extra1 = SYSCTL_ONE }, #endif
--
2.43.0