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ipmr: add rcu protection over (struct vif_device)->dev
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We will soon use RCU instead of rwlock in ipmr & ip6mr

This preliminary patch adds proper rcu verbs to read/write
(struct vif_device)->dev

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Jun 24, 2022
1 parent 0a24c43 commit ebc3197
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Showing 4 changed files with 111 additions and 77 deletions.
11 changes: 7 additions & 4 deletions include/linux/mroute_base.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@
* @remote: Remote address for tunnels
*/
struct vif_device {
struct net_device *dev;
struct net_device __rcu *dev;
netdevice_tracker dev_tracker;
unsigned long bytes_in, bytes_out;
unsigned long pkt_in, pkt_out;
Expand All @@ -52,6 +52,7 @@ static inline int mr_call_vif_notifier(struct notifier_block *nb,
unsigned short family,
enum fib_event_type event_type,
struct vif_device *vif,
struct net_device *vif_dev,
unsigned short vif_index, u32 tb_id,
struct netlink_ext_ack *extack)
{
Expand All @@ -60,7 +61,7 @@ static inline int mr_call_vif_notifier(struct notifier_block *nb,
.family = family,
.extack = extack,
},
.dev = vif->dev,
.dev = vif_dev,
.vif_index = vif_index,
.vif_flags = vif->flags,
.tb_id = tb_id,
Expand All @@ -73,14 +74,15 @@ static inline int mr_call_vif_notifiers(struct net *net,
unsigned short family,
enum fib_event_type event_type,
struct vif_device *vif,
struct net_device *vif_dev,
unsigned short vif_index, u32 tb_id,
unsigned int *ipmr_seq)
{
struct vif_entry_notifier_info info = {
.info = {
.family = family,
},
.dev = vif->dev,
.dev = vif_dev,
.vif_index = vif_index,
.vif_flags = vif->flags,
.tb_id = tb_id,
Expand All @@ -98,7 +100,8 @@ static inline int mr_call_vif_notifiers(struct net *net,
#define MAXVIFS 32
#endif

#define VIF_EXISTS(_mrt, _idx) (!!((_mrt)->vif_table[_idx].dev))
/* Note: This helper is deprecated. */
#define VIF_EXISTS(_mrt, _idx) (!!rcu_access_pointer((_mrt)->vif_table[_idx].dev))

/* mfc_flags:
* MFC_STATIC - the entry was added statically (not by a routing daemon)
Expand Down
65 changes: 38 additions & 27 deletions net/ipv4/ipmr.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,12 @@ struct ipmr_result {

static DEFINE_RWLOCK(mrt_lock);

static struct net_device *vif_dev_read(const struct vif_device *vif)
{
return rcu_dereference_check(vif->dev,
lockdep_is_held(&mrt_lock));
}

/* Multicast router control variables */

/* Special spinlock for queue of unresolved entries */
Expand Down Expand Up @@ -586,7 +592,7 @@ static int __pim_rcv(struct mr_table *mrt, struct sk_buff *skb,

read_lock(&mrt_lock);
if (mrt->mroute_reg_vif_num >= 0)
reg_dev = mrt->vif_table[mrt->mroute_reg_vif_num].dev;
reg_dev = vif_dev_read(&mrt->vif_table[mrt->mroute_reg_vif_num]);
read_unlock(&mrt_lock);

if (!reg_dev)
Expand Down Expand Up @@ -614,10 +620,11 @@ static struct net_device *ipmr_reg_vif(struct net *net, struct mr_table *mrt)
static int call_ipmr_vif_entry_notifiers(struct net *net,
enum fib_event_type event_type,
struct vif_device *vif,
struct net_device *vif_dev,
vifi_t vif_index, u32 tb_id)
{
return mr_call_vif_notifiers(net, RTNL_FAMILY_IPMR, event_type,
vif, vif_index, tb_id,
vif, vif_dev, vif_index, tb_id,
&net->ipv4.ipmr_seq);
}

Expand Down Expand Up @@ -649,18 +656,14 @@ static int vif_delete(struct mr_table *mrt, int vifi, int notify,

v = &mrt->vif_table[vifi];

if (VIF_EXISTS(mrt, vifi))
call_ipmr_vif_entry_notifiers(net, FIB_EVENT_VIF_DEL, v, vifi,
mrt->id);
dev = rtnl_dereference(v->dev);
if (!dev)
return -EADDRNOTAVAIL;

write_lock_bh(&mrt_lock);
dev = v->dev;
v->dev = NULL;

if (!dev) {
write_unlock_bh(&mrt_lock);
return -EADDRNOTAVAIL;
}
call_ipmr_vif_entry_notifiers(net, FIB_EVENT_VIF_DEL, v, dev,
vifi, mrt->id);
RCU_INIT_POINTER(v->dev, NULL);

if (vifi == mrt->mroute_reg_vif_num)
mrt->mroute_reg_vif_num = -1;
Expand Down Expand Up @@ -890,14 +893,15 @@ static int vif_add(struct net *net, struct mr_table *mrt,

/* And finish update writing critical data */
write_lock_bh(&mrt_lock);
v->dev = dev;
rcu_assign_pointer(v->dev, dev);
netdev_tracker_alloc(dev, &v->dev_tracker, GFP_ATOMIC);
if (v->flags & VIFF_REGISTER)
mrt->mroute_reg_vif_num = vifi;
if (vifi+1 > mrt->maxvif)
mrt->maxvif = vifi+1;
write_unlock_bh(&mrt_lock);
call_ipmr_vif_entry_notifiers(net, FIB_EVENT_VIF_ADD, v, vifi, mrt->id);
call_ipmr_vif_entry_notifiers(net, FIB_EVENT_VIF_ADD, v, dev,
vifi, mrt->id);
return 0;
}

Expand Down Expand Up @@ -1726,7 +1730,7 @@ static int ipmr_device_event(struct notifier_block *this, unsigned long event, v
ipmr_for_each_table(mrt, net) {
v = &mrt->vif_table[0];
for (ct = 0; ct < mrt->maxvif; ct++, v++) {
if (v->dev == dev)
if (rcu_access_pointer(v->dev) == dev)
vif_delete(mrt, ct, 1, NULL);
}
}
Expand Down Expand Up @@ -1811,19 +1815,21 @@ static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt,
{
const struct iphdr *iph = ip_hdr(skb);
struct vif_device *vif = &mrt->vif_table[vifi];
struct net_device *vif_dev;
struct net_device *dev;
struct rtable *rt;
struct flowi4 fl4;
int encap = 0;

if (!vif->dev)
vif_dev = vif_dev_read(vif);
if (!vif_dev)
goto out_free;

if (vif->flags & VIFF_REGISTER) {
vif->pkt_out++;
vif->bytes_out += skb->len;
vif->dev->stats.tx_bytes += skb->len;
vif->dev->stats.tx_packets++;
vif_dev->stats.tx_bytes += skb->len;
vif_dev->stats.tx_packets++;
ipmr_cache_report(mrt, skb, vifi, IGMPMSG_WHOLEPKT);
goto out_free;
}
Expand Down Expand Up @@ -1881,8 +1887,8 @@ static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt,
if (vif->flags & VIFF_TUNNEL) {
ip_encap(net, skb, vif->local, vif->remote);
/* FIXME: extra output firewall step used to be here. --RR */
vif->dev->stats.tx_packets++;
vif->dev->stats.tx_bytes += skb->len;
vif_dev->stats.tx_packets++;
vif_dev->stats.tx_bytes += skb->len;
}

IPCB(skb)->flags |= IPSKB_FORWARDED;
Expand Down Expand Up @@ -1911,7 +1917,7 @@ static int ipmr_find_vif(struct mr_table *mrt, struct net_device *dev)
int ct;

for (ct = mrt->maxvif-1; ct >= 0; ct--) {
if (mrt->vif_table[ct].dev == dev)
if (rcu_access_pointer(mrt->vif_table[ct].dev) == dev)
break;
}
return ct;
Expand Down Expand Up @@ -1944,7 +1950,7 @@ static void ip_mr_forward(struct net *net, struct mr_table *mrt,
}

/* Wrong interface: drop packet and (maybe) send PIM assert. */
if (mrt->vif_table[vif].dev != dev) {
if (rcu_access_pointer(mrt->vif_table[vif].dev) != dev) {
if (rt_is_output_route(skb_rtable(skb))) {
/* It is our own packet, looped back.
* Very complicated situation...
Expand Down Expand Up @@ -2744,18 +2750,21 @@ static bool ipmr_fill_table(struct mr_table *mrt, struct sk_buff *skb)

static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb)
{
struct net_device *vif_dev;
struct nlattr *vif_nest;
struct vif_device *vif;

vif = &mrt->vif_table[vifid];
vif_dev = vif_dev_read(vif);
/* if the VIF doesn't exist just continue */
if (!VIF_EXISTS(mrt, vifid))
if (!vif_dev)
return true;

vif = &mrt->vif_table[vifid];
vif_nest = nla_nest_start_noflag(skb, IPMRA_VIF);
if (!vif_nest)
return false;
if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, vif->dev->ifindex) ||

if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, 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,
Expand Down Expand Up @@ -2919,9 +2928,11 @@ static int ipmr_vif_seq_show(struct seq_file *seq, void *v)
"Interface BytesIn PktsIn BytesOut PktsOut Flags Local Remote\n");
} else {
const struct vif_device *vif = v;
const char *name = vif->dev ?
vif->dev->name : "none";
const struct net_device *vif_dev;
const char *name;

vif_dev = vif_dev_read(vif);
name = vif_dev ? vif_dev->name : "none";
seq_printf(seq,
"%2td %-10s %8ld %7ld %8ld %7ld %05X %08X %08X\n",
vif - mrt->vif_table,
Expand Down
49 changes: 31 additions & 18 deletions net/ipv4/ipmr_base.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ void vif_device_init(struct vif_device *v,
unsigned short flags,
unsigned short get_iflink_mask)
{
v->dev = NULL;
RCU_INIT_POINTER(v->dev, NULL);
v->bytes_in = 0;
v->bytes_out = 0;
v->pkt_in = 0;
Expand Down Expand Up @@ -208,6 +208,7 @@ EXPORT_SYMBOL(mr_mfc_seq_next);
int mr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
struct mr_mfc *c, struct rtmsg *rtm)
{
struct net_device *vif_dev;
struct rta_mfc_stats mfcs;
struct nlattr *mp_attr;
struct rtnexthop *nhp;
Expand All @@ -220,10 +221,13 @@ int mr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
return -ENOENT;
}

if (VIF_EXISTS(mrt, c->mfc_parent) &&
nla_put_u32(skb, RTA_IIF,
mrt->vif_table[c->mfc_parent].dev->ifindex) < 0)
rcu_read_lock();
vif_dev = rcu_dereference(mrt->vif_table[c->mfc_parent].dev);
if (vif_dev && nla_put_u32(skb, RTA_IIF, vif_dev->ifindex) < 0) {
rcu_read_unlock();
return -EMSGSIZE;
}
rcu_read_unlock();

if (c->mfc_flags & MFC_OFFLOAD)
rtm->rtm_flags |= RTNH_F_OFFLOAD;
Expand All @@ -232,23 +236,27 @@ int mr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
if (!mp_attr)
return -EMSGSIZE;

rcu_read_lock();
for (ct = c->mfc_un.res.minvif; ct < c->mfc_un.res.maxvif; ct++) {
if (VIF_EXISTS(mrt, ct) && c->mfc_un.res.ttls[ct] < 255) {
struct vif_device *vif;
struct vif_device *vif = &mrt->vif_table[ct];

vif_dev = rcu_dereference(vif->dev);
if (vif_dev && c->mfc_un.res.ttls[ct] < 255) {

nhp = nla_reserve_nohdr(skb, sizeof(*nhp));
if (!nhp) {
rcu_read_unlock();
nla_nest_cancel(skb, mp_attr);
return -EMSGSIZE;
}

nhp->rtnh_flags = 0;
nhp->rtnh_hops = c->mfc_un.res.ttls[ct];
vif = &mrt->vif_table[ct];
nhp->rtnh_ifindex = vif->dev->ifindex;
nhp->rtnh_ifindex = vif_dev->ifindex;
nhp->rtnh_len = sizeof(*nhp);
}
}
rcu_read_unlock();

nla_nest_end(skb, mp_attr);

Expand All @@ -275,13 +283,14 @@ static bool mr_mfc_uses_dev(const struct mr_table *mrt,
int ct;

for (ct = c->mfc_un.res.minvif; ct < c->mfc_un.res.maxvif; ct++) {
if (VIF_EXISTS(mrt, ct) && c->mfc_un.res.ttls[ct] < 255) {
const struct vif_device *vif;

vif = &mrt->vif_table[ct];
if (vif->dev == dev)
return true;
}
const struct net_device *vif_dev;
const struct vif_device *vif;

vif = &mrt->vif_table[ct];
vif_dev = rcu_access_pointer(vif->dev);
if (vif_dev && c->mfc_un.res.ttls[ct] < 255 &&
vif_dev == dev)
return true;
}
return false;
}
Expand Down Expand Up @@ -402,18 +411,22 @@ int mr_dump(struct net *net, struct notifier_block *nb, unsigned short family,

for (mrt = mr_iter(net, NULL); mrt; mrt = mr_iter(net, mrt)) {
struct vif_device *v = &mrt->vif_table[0];
struct net_device *vif_dev;
struct mr_mfc *mfc;
int vifi;

/* Notifiy on table VIF entries */
read_lock(mrt_lock);
for (vifi = 0; vifi < mrt->maxvif; vifi++, v++) {
if (!v->dev)
vif_dev = rcu_dereference_check(v->dev,
lockdep_is_held(mrt_lock));
if (!vif_dev)
continue;

err = mr_call_vif_notifier(nb, family,
FIB_EVENT_VIF_ADD,
v, vifi, mrt->id, extack);
FIB_EVENT_VIF_ADD, v,
vif_dev, vifi,
mrt->id, extack);
if (err)
break;
}
Expand Down
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