Re: [PATCH 4.4 002/193] net: replace dst_cache ip6_tunnel implementation with the generic one

From: Nathan Chancellor
Date: Fri Feb 23 2018 - 18:00:29 EST

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In reply to: Greg Kroah-Hartman: "[PATCH 4.4 002/193] net: replace dst_cache ip6_tunnel implementation with the generic one"
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On Fri, Feb 23, 2018 at 07:23:55PM +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Paolo Abeni <pabeni@xxxxxxxxxx>
>
> commit 607f725f6f7d5ec3759fbc16224afb60e2152a5b upstream.
>
> This also fix a potential race into the existing tunnel code, which
> could lead to the wrong dst to be permanenty cached:
>
> CPU1: CPU2:
> <xmit on ip6_tunnel>
> <cache lookup fails>
> dst = ip6_route_output(...)
> <tunnel params are changed via nl>
> dst_cache_reset() // no effect,
> // the cache is empty
> dst_cache_set() // the wrong dst
> // is permanenty stored
> // into the cache
>
> With the new dst implementation the above race is not possible
> since the first cache lookup after dst_cache_reset will fail due
> to the timestamp check
>
> Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
> Suggested-and-acked-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Manoj Boopathi Raj <manojboopathi@xxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>
> ---
> include/net/ip6_tunnel.h | 15 ----
> net/ipv6/Kconfig | 1
> net/ipv6/ip6_gre.c | 12 +--
> net/ipv6/ip6_tunnel.c | 151 +++++++----------------------------------------
> net/ipv6/ip6_vti.c | 2
> 5 files changed, 35 insertions(+), 146 deletions(-)
>
> --- a/include/net/ip6_tunnel.h
> +++ b/include/net/ip6_tunnel.h
> @@ -5,6 +5,8 @@
> #include <linux/netdevice.h>
> #include <linux/if_tunnel.h>
> #include <linux/ip6_tunnel.h>
> +#include <net/ip_tunnels.h>
> +#include <net/dst_cache.h>
>
> #define IP6TUNNEL_ERR_TIMEO (30*HZ)
>
> @@ -32,12 +34,6 @@ struct __ip6_tnl_parm {
> __be32 o_key;
> };
>
> -struct ip6_tnl_dst {
> - seqlock_t lock;
> - struct dst_entry __rcu *dst;
> - u32 cookie;
> -};
> -
> /* IPv6 tunnel */
> struct ip6_tnl {
> struct ip6_tnl __rcu *next; /* next tunnel in list */
> @@ -45,7 +41,7 @@ struct ip6_tnl {
> struct net *net; /* netns for packet i/o */
> struct __ip6_tnl_parm parms; /* tunnel configuration parameters */
> struct flowi fl; /* flowi template for xmit */
> - struct ip6_tnl_dst __percpu *dst_cache; /* cached dst */
> + struct dst_cache dst_cache; /* cached dst */
>
> int err_count;
> unsigned long err_time;
> @@ -65,11 +61,6 @@ struct ipv6_tlv_tnl_enc_lim {
> __u8 encap_limit; /* tunnel encapsulation limit */
> } __packed;
>
> -struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t);
> -int ip6_tnl_dst_init(struct ip6_tnl *t);
> -void ip6_tnl_dst_destroy(struct ip6_tnl *t);
> -void ip6_tnl_dst_reset(struct ip6_tnl *t);
> -void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst);
> int ip6_tnl_rcv_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,
> const struct in6_addr *raddr);
> int ip6_tnl_xmit_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,
> --- a/net/ipv6/Kconfig
> +++ b/net/ipv6/Kconfig
> @@ -205,6 +205,7 @@ config IPV6_NDISC_NODETYPE
> config IPV6_TUNNEL
> tristate "IPv6: IP-in-IPv6 tunnel (RFC2473)"
> select INET6_TUNNEL
> + select DST_CACHE
> ---help---
> Support for IPv6-in-IPv6 and IPv4-in-IPv6 tunnels described in
> RFC 2473.
> --- a/net/ipv6/ip6_gre.c
> +++ b/net/ipv6/ip6_gre.c
> @@ -362,7 +362,7 @@ static void ip6gre_tunnel_uninit(struct
> struct ip6gre_net *ign = net_generic(t->net, ip6gre_net_id);
>
> ip6gre_tunnel_unlink(ign, t);
> - ip6_tnl_dst_reset(t);
> + dst_cache_reset(&t->dst_cache);
> dev_put(dev);
> }
>
> @@ -640,7 +640,7 @@ static netdev_tx_t ip6gre_xmit2(struct s
> }
>
> if (!fl6->flowi6_mark)
> - dst = ip6_tnl_dst_get(tunnel);
> + dst = dst_cache_get(&tunnel->dst_cache);
>
> if (!dst) {
> dst = ip6_route_output(net, NULL, fl6);
> @@ -709,7 +709,7 @@ static netdev_tx_t ip6gre_xmit2(struct s
> }
>
> if (!fl6->flowi6_mark && ndst)
> - ip6_tnl_dst_set(tunnel, ndst);
> + dst_cache_set_ip6(&tunnel->dst_cache, ndst, &fl6->saddr);
> skb_dst_set(skb, dst);
>
> proto = NEXTHDR_GRE;
> @@ -1017,7 +1017,7 @@ static int ip6gre_tnl_change(struct ip6_
> t->parms.o_key = p->o_key;
> t->parms.i_flags = p->i_flags;
> t->parms.o_flags = p->o_flags;
> - ip6_tnl_dst_reset(t);
> + dst_cache_reset(&t->dst_cache);
> ip6gre_tnl_link_config(t, set_mtu);
> return 0;
> }
> @@ -1228,7 +1228,7 @@ static void ip6gre_dev_free(struct net_d
> {
> struct ip6_tnl *t = netdev_priv(dev);
>
> - ip6_tnl_dst_destroy(t);
> + dst_cache_destroy(&t->dst_cache);
> free_percpu(dev->tstats);
> free_netdev(dev);
> }
> @@ -1266,7 +1266,7 @@ static int ip6gre_tunnel_init_common(str
> if (!dev->tstats)
> return -ENOMEM;
>
> - ret = ip6_tnl_dst_init(tunnel);
> + ret = dst_cache_init(&tunnel->dst_cache, GFP_KERNEL);
> if (ret) {
> free_percpu(dev->tstats);
> dev->tstats = NULL;
> --- a/net/ipv6/ip6_tunnel.c
> +++ b/net/ipv6/ip6_tunnel.c
> @@ -122,97 +122,6 @@ static struct net_device_stats *ip6_get_
> return &dev->stats;
> }
>
> -/*
> - * Locking : hash tables are protected by RCU and RTNL
> - */
> -
> -static void ip6_tnl_per_cpu_dst_set(struct ip6_tnl_dst *idst,
> - struct dst_entry *dst)
> -{
> - write_seqlock_bh(&idst->lock);
> - dst_release(rcu_dereference_protected(
> - idst->dst,
> - lockdep_is_held(&idst->lock.lock)));
> - if (dst) {
> - dst_hold(dst);
> - idst->cookie = rt6_get_cookie((struct rt6_info *)dst);
> - } else {
> - idst->cookie = 0;
> - }
> - rcu_assign_pointer(idst->dst, dst);
> - write_sequnlock_bh(&idst->lock);
> -}
> -
> -struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t)
> -{
> - struct ip6_tnl_dst *idst;
> - struct dst_entry *dst;
> - unsigned int seq;
> - u32 cookie;
> -
> - idst = raw_cpu_ptr(t->dst_cache);
> -
> - rcu_read_lock();
> - do {
> - seq = read_seqbegin(&idst->lock);
> - dst = rcu_dereference(idst->dst);
> - cookie = idst->cookie;
> - } while (read_seqretry(&idst->lock, seq));
> -
> - if (dst && !atomic_inc_not_zero(&dst->__refcnt))
> - dst = NULL;
> - rcu_read_unlock();
> -
> - if (dst && dst->obsolete && !dst->ops->check(dst, cookie)) {
> - ip6_tnl_per_cpu_dst_set(idst, NULL);
> - dst_release(dst);
> - dst = NULL;
> - }
> - return dst;
> -}
> -EXPORT_SYMBOL_GPL(ip6_tnl_dst_get);
> -
> -void ip6_tnl_dst_reset(struct ip6_tnl *t)
> -{
> - int i;
> -
> - for_each_possible_cpu(i)
> - ip6_tnl_per_cpu_dst_set(per_cpu_ptr(t->dst_cache, i), NULL);
> -}
> -EXPORT_SYMBOL_GPL(ip6_tnl_dst_reset);
> -
> -void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst)
> -{
> - ip6_tnl_per_cpu_dst_set(raw_cpu_ptr(t->dst_cache), dst);
> -
> -}
> -EXPORT_SYMBOL_GPL(ip6_tnl_dst_set);
> -
> -void ip6_tnl_dst_destroy(struct ip6_tnl *t)
> -{
> - if (!t->dst_cache)
> - return;
> -
> - ip6_tnl_dst_reset(t);
> - free_percpu(t->dst_cache);
> -}
> -EXPORT_SYMBOL_GPL(ip6_tnl_dst_destroy);
> -
> -int ip6_tnl_dst_init(struct ip6_tnl *t)
> -{
> - int i;
> -
> - t->dst_cache = alloc_percpu(struct ip6_tnl_dst);
> - if (!t->dst_cache)
> - return -ENOMEM;
> -
> - for_each_possible_cpu(i)
> - seqlock_init(&per_cpu_ptr(t->dst_cache, i)->lock);
> -
> - return 0;
> -}
> -EXPORT_SYMBOL_GPL(ip6_tnl_dst_init);
> -
> /**
> * ip6_tnl_lookup - fetch tunnel matching the end-point addresses
> * @remote: the address of the tunnel exit-point
> @@ -331,7 +240,7 @@ static void ip6_dev_free(struct net_devi
> {
> struct ip6_tnl *t = netdev_priv(dev);
>
> - ip6_tnl_dst_destroy(t);
> + dst_cache_destroy(&t->dst_cache);
> free_percpu(dev->tstats);
> free_netdev(dev);
> }
> @@ -464,7 +373,7 @@ ip6_tnl_dev_uninit(struct net_device *de
> RCU_INIT_POINTER(ip6n->tnls_wc[0], NULL);
> else
> ip6_tnl_unlink(ip6n, t);
> - ip6_tnl_dst_reset(t);
> + dst_cache_reset(&t->dst_cache);
> dev_put(dev);
> }
>
> @@ -1053,7 +962,6 @@ static int ip6_tnl_xmit2(struct sk_buff
> struct ipv6_tel_txoption opt;
> struct dst_entry *dst = NULL, *ndst = NULL;
> struct net_device *tdev;
> - bool use_cache = false;
> int mtu;
> unsigned int max_headroom = sizeof(struct ipv6hdr);
> u8 proto;
> @@ -1061,39 +969,28 @@ static int ip6_tnl_xmit2(struct sk_buff
>
> /* NBMA tunnel */
> if (ipv6_addr_any(&t->parms.raddr)) {
> - if (skb->protocol == htons(ETH_P_IPV6)) {
> - struct in6_addr *addr6;
> - struct neighbour *neigh;
> - int addr_type;
> -
> - if (!skb_dst(skb))
> - goto tx_err_link_failure;
> -
> - neigh = dst_neigh_lookup(skb_dst(skb),
> - &ipv6_hdr(skb)->daddr);
> - if (!neigh)
> - goto tx_err_link_failure;
> + struct in6_addr *addr6;
> + struct neighbour *neigh;
> + int addr_type;
> +
> + if (!skb_dst(skb))
> + goto tx_err_link_failure;
>
> - addr6 = (struct in6_addr *)&neigh->primary_key;
> - addr_type = ipv6_addr_type(addr6);
> + neigh = dst_neigh_lookup(skb_dst(skb),
> + &ipv6_hdr(skb)->daddr);
> + if (!neigh)
> + goto tx_err_link_failure;
>
> - if (addr_type == IPV6_ADDR_ANY)
> - addr6 = &ipv6_hdr(skb)->daddr;
> + addr6 = (struct in6_addr *)&neigh->primary_key;
> + addr_type = ipv6_addr_type(addr6);
>
> - memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
> - neigh_release(neigh);
> - }
> - } else if (t->parms.proto != 0 && !(t->parms.flags &
> - (IP6_TNL_F_USE_ORIG_TCLASS |
> - IP6_TNL_F_USE_ORIG_FWMARK))) {
> - /* enable the cache only if neither the outer protocol nor the
> - * routing decision depends on the current inner header value
> - */
> - use_cache = true;
> - }
> + if (addr_type == IPV6_ADDR_ANY)
> + addr6 = &ipv6_hdr(skb)->daddr;
>
> - if (use_cache)
> - dst = ip6_tnl_dst_get(t);
> + memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
> + neigh_release(neigh);
> + } else if (!fl6->flowi6_mark)
> + dst = dst_cache_get(&t->dst_cache);
>
> if (!ip6_tnl_xmit_ctl(t, &fl6->saddr, &fl6->daddr))
> goto tx_err_link_failure;
> @@ -1156,8 +1053,8 @@ static int ip6_tnl_xmit2(struct sk_buff
> skb = new_skb;
> }
>
> - if (use_cache && ndst)
> - ip6_tnl_dst_set(t, ndst);
> + if (!fl6->flowi6_mark && ndst)
> + dst_cache_set_ip6(&t->dst_cache, ndst, &fl6->saddr);
> skb_dst_set(skb, dst);
>
> skb->transport_header = skb->network_header;
> @@ -1392,7 +1289,7 @@ ip6_tnl_change(struct ip6_tnl *t, const
> t->parms.flowinfo = p->flowinfo;
> t->parms.link = p->link;
> t->parms.proto = p->proto;
> - ip6_tnl_dst_reset(t);
> + dst_cache_reset(&t->dst_cache);
> ip6_tnl_link_config(t);
> return 0;
> }
> @@ -1663,7 +1560,7 @@ ip6_tnl_dev_init_gen(struct net_device *
> if (!dev->tstats)
> return -ENOMEM;
>
> - ret = ip6_tnl_dst_init(t);
> + ret = dst_cache_init(&t->dst_cache, GFP_KERNEL);
> if (ret) {
> free_percpu(dev->tstats);
> dev->tstats = NULL;
> --- a/net/ipv6/ip6_vti.c
> +++ b/net/ipv6/ip6_vti.c
> @@ -645,7 +645,7 @@ vti6_tnl_change(struct ip6_tnl *t, const
> t->parms.i_key = p->i_key;
> t->parms.o_key = p->o_key;
> t->parms.proto = p->proto;
> - ip6_tnl_dst_reset(t);
> + dst_cache_reset(&t->dst_cache);
> vti6_link_config(t);
> return 0;
> }
>
>

It may also be wise to take these two commits from mainline, as they
are along the same lines as this one:

09acddf873b ("ip_tunnel: replace dst_cache with generic implementation")
27337e16f2d ("ip_tunnel: fix preempt warning in ip tunnel creation/updating")

There is a minor conflict with the first one due to stable commit
6f99825e7632 ("sit: fix a double free on error path").

I'll most likely carry them anyways, it fixes a build error with some
out of tree code but less out of tree code I have, the better!

Thanks!
Nathan

Next message: Bjorn Helgaas: "Re: [PATCH v11 0/7] Address error and recovery for AER and DPC"
Previous message: Khalid Aziz: "[PATCH v13 10/11] sparc64: Add support for ADI (Application Data Integrity)"
In reply to: Greg Kroah-Hartman: "[PATCH 4.4 002/193] net: replace dst_cache ip6_tunnel implementation with the generic one"
Next in thread: Greg Kroah-Hartman: "[PATCH 4.4 023/193] arm64: dts: add #cooling-cells to CPU nodes"
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