[PATCH v3 net-next 03/15] ipmr: Convert ipmr_rtm_dumplink() to RCU.
From: Kuniyuki Iwashima <kuniyu@google.com>
Date: 2026-02-28 22:18:08
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
net->ipv4.mr_tables is updated under RTNL and can be read safely under RCU. Once created, the multicast route tables are not removed until netns dismantle. ipmr_rtm_dumplink() does not need RTNL protection for ipmr_for_each_table() and ipmr_fill_table() if RCU is held. Even if mrt->maxvif changes concurrently, ipmr_fill_vif() returns true to continue dumping the next table. Let's convert it to RCU. Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> --- v2: Add READ_ONCE() for mrt->maxvif in ipmr_rtm_dumplink(). --- net/ipv4/ipmr.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-)
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 970f173654c7..eecc79a835d1 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c@@ -2901,12 +2901,13 @@ static bool ipmr_fill_table(struct mr_table *mrt, struct sk_buff *skb) if (nla_put_u32(skb, IPMRA_TABLE_ID, mrt->id) || nla_put_u32(skb, IPMRA_TABLE_CACHE_RES_QUEUE_LEN, queue_len) || nla_put_s32(skb, IPMRA_TABLE_MROUTE_REG_VIF_NUM, - mrt->mroute_reg_vif_num) || + READ_ONCE(mrt->mroute_reg_vif_num)) || nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_ASSERT, - mrt->mroute_do_assert) || - nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_PIM, mrt->mroute_do_pim) || + READ_ONCE(mrt->mroute_do_assert)) || + nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_PIM, + READ_ONCE(mrt->mroute_do_pim)) || nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_WRVIFWHOLE, - mrt->mroute_do_wrvifwhole)) + READ_ONCE(mrt->mroute_do_wrvifwhole))) return false; return true;
@@ -2919,7 +2920,7 @@ static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb) struct vif_device *vif; vif = &mrt->vif_table[vifid]; - vif_dev = rtnl_dereference(vif->dev); + vif_dev = vif_dev_read(vif); /* if the VIF doesn't exist just continue */ if (!vif_dev) return true;
@@ -2928,16 +2929,16 @@ static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb) if (!vif_nest) return false; - if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, vif_dev->ifindex) || + if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, READ_ONCE(vif_dev->ifindex)) || nla_put_u32(skb, IPMRA_VIFA_VIF_ID, vifid) || nla_put_u16(skb, IPMRA_VIFA_FLAGS, vif->flags) || - nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_IN, vif->bytes_in, + nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_IN, READ_ONCE(vif->bytes_in), IPMRA_VIFA_PAD) || - nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_OUT, vif->bytes_out, + nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_OUT, READ_ONCE(vif->bytes_out), IPMRA_VIFA_PAD) || - nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_IN, vif->pkt_in, + nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_IN, READ_ONCE(vif->pkt_in), IPMRA_VIFA_PAD) || - nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_OUT, vif->pkt_out, + nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_OUT, READ_ONCE(vif->pkt_out), IPMRA_VIFA_PAD) || nla_put_be32(skb, IPMRA_VIFA_LOCAL_ADDR, vif->local) || nla_put_be32(skb, IPMRA_VIFA_REMOTE_ADDR, vif->remote)) {
@@ -2992,6 +2993,8 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb) s_t = cb->args[0]; s_e = cb->args[1]; + rcu_read_lock(); + ipmr_for_each_table(mrt, net) { struct nlattr *vifs, *af; struct ifinfomsg *hdr;
@@ -3026,7 +3029,7 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb) nlmsg_end(skb, nlh); goto out; } - for (i = 0; i < mrt->maxvif; i++) { + for (i = 0; i < READ_ONCE(mrt->maxvif); i++) { if (e < s_e) goto skip_entry; if (!ipmr_fill_vif(mrt, i, skb)) {
@@ -3048,6 +3051,8 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb) } out: + rcu_read_unlock(); + cb->args[1] = e; cb->args[0] = t;
@@ -3287,7 +3292,7 @@ static struct pernet_operations ipmr_net_ops = { static const struct rtnl_msg_handler ipmr_rtnl_msg_handlers[] __initconst = { {.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_GETLINK, - .dumpit = ipmr_rtm_dumplink}, + .dumpit = ipmr_rtm_dumplink, .flags = RTNL_FLAG_DUMP_UNLOCKED}, {.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_NEWROUTE, .doit = ipmr_rtm_route}, {.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_DELROUTE,
--
2.53.0.473.g4a7958ca14-goog