Re: [PATCH RFC net-next] ipv6: Kill ipv6 dependency of icmpv6_send().

Eric Dumazet
2013-04-24T00:05:54Z

On Tue, 2013-04-23 at 16:49 -0700, Pravin B Shelar wrote:
> Following patch adds icmp-registration module for ipv6. It allows
> ipv6 protocol to register icmp_sender which is used for sending
> ipv6 icmp msgs. This extra layer allows us to kill dependency
> on ipv6 for icmpv6_send() function.
>
> This patch also fixes ip_tunnel compilation problem when ip_tunnel
> is statically compiled in kernel but ipv6 is module.
>
> Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
> ---
> include/linux/icmpv6.h | 18 +++++++++++--
> net/ipv6/Makefile | 2 +-
> net/ipv6/icmp.c | 35 +++++++++++++++-----------
> net/ipv6/ip6_icmp.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 100 insertions(+), 19 deletions(-)
> create mode 100644 net/ipv6/ip6_icmp.c
>
> diff --git a/include/linux/icmpv6.h b/include/linux/icmpv6.h
> index b4f6c29..630f453 100644
> --- a/include/linux/icmpv6.h
> +++ b/include/linux/icmpv6.h
> @@ -11,9 +11,21 @@ static inline struct icmp6hdr *icmp6_hdr(const struct sk_buff *skb)
>
> #include <linux/netdevice.h>
>
> -extern void icmpv6_send(struct sk_buff *skb,
> - u8 type, u8 code,
> - __u32 info);
> +#if IS_ENABLED(CONFIG_IPV6)
> +extern void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info);
> +
> +typedef void ip6_icmp_send_t(struct sk_buff *skb, u8 type, u8 code, __u32 info);
> +extern int inet6_register_icmp_sender(ip6_icmp_send_t *fn);
> +extern int inet6_unregister_icmp_sender(ip6_icmp_send_t *fn);
> +
> +#else
> +
> +static inline void icmpv6_send(struct sk_buff *skb,
> + u8 type, u8 code, __u32 info)
> +{
> +
> +}
> +#endif
>
> extern int icmpv6_init(void);
> extern int icmpv6_err_convert(u8 type, u8 code,
> diff --git a/net/ipv6/Makefile b/net/ipv6/Makefile
> index 309af19..9af088d 100644
> --- a/net/ipv6/Makefile
> +++ b/net/ipv6/Makefile
> @@ -40,7 +40,7 @@ obj-$(CONFIG_IPV6_SIT) += sit.o
> obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.o
> obj-$(CONFIG_IPV6_GRE) += ip6_gre.o
>
> -obj-y += addrconf_core.o exthdrs_core.o ip6_checksum.o
> +obj-y += addrconf_core.o exthdrs_core.o ip6_checksum.o ip6_icmp.o
> obj-$(CONFIG_INET) += output_core.o protocol.o $(ipv6-offload)
>
> obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o
> diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
> index 71b900c..2a53a79 100644
> --- a/net/ipv6/icmp.c
> +++ b/net/ipv6/icmp.c
> @@ -124,15 +124,6 @@ static __inline__ void icmpv6_xmit_unlock(struct sock *sk)
> }
>
> /*
> - * Slightly more convenient version of icmpv6_send.
> - */
> -void icmpv6_param_prob(struct sk_buff *skb, u8 code, int pos)
> -{
> - icmpv6_send(skb, ICMPV6_PARAMPROB, code, pos);
> - kfree_skb(skb);
> -}
> -
> -/*
> * Figure out, may we reply to this packet with icmp error.
> *
> * We do not reply, if:
> @@ -332,7 +323,7 @@ static struct dst_entry *icmpv6_route_lookup(struct net *net, struct sk_buff *sk
> * anycast.
> */
> if (((struct rt6_info *)dst)->rt6i_flags & RTF_ANYCAST) {
> - LIMIT_NETDEBUG(KERN_DEBUG "icmpv6_send: acast source\n");
> + LIMIT_NETDEBUG(KERN_DEBUG "icmp6_send: acast source\n");
> dst_release(dst);
> return ERR_PTR(-EINVAL);
> }
> @@ -381,7 +372,7 @@ relookup_failed:
> /*
> * Send an ICMP message in response to a packet in error
> */
> -void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
> +static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
> {
> struct net *net = dev_net(skb->dev);
> struct inet6_dev *idev = NULL;
> @@ -406,7 +397,7 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
> /*
> * Make sure we respect the rules
> * i.e. RFC 1885 2.4(e)
> - * Rule (e.1) is enforced by not using icmpv6_send
> + * Rule (e.1) is enforced by not using icmp6_send
> * in any code that processes icmp errors.
> */
> addr_type = ipv6_addr_type(&hdr->daddr);
> @@ -444,7 +435,7 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
> * and anycast addresses will be checked later.
> */
> if ((addr_type == IPV6_ADDR_ANY) || (addr_type & IPV6_ADDR_MULTICAST)) {
> - LIMIT_NETDEBUG(KERN_DEBUG "icmpv6_send: addr_any/mcast source\n");
> + LIMIT_NETDEBUG(KERN_DEBUG "icmp6_send: addr_any/mcast source\n");
> return;
> }
>
> @@ -452,7 +443,7 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
> * Never answer to a ICMP packet.
> */
> if (is_ineligible(skb)) {
> - LIMIT_NETDEBUG(KERN_DEBUG "icmpv6_send: no reply to icmp error\n");
> + LIMIT_NETDEBUG(KERN_DEBUG "icmp6_send: no reply to icmp error\n");
> return;
> }
>
> @@ -529,7 +520,14 @@ out_dst_release:
> out:
> icmpv6_xmit_unlock(sk);
> }
> -EXPORT_SYMBOL(icmpv6_send);
> +
> +/* Slightly more convenient version of icmp6_send.
> + */
> +void icmpv6_param_prob(struct sk_buff *skb, u8 code, int pos)
> +{
> + icmp6_send(skb, ICMPV6_PARAMPROB, code, pos);
> + kfree_skb(skb);
> +}
>
> static void icmpv6_echo_reply(struct sk_buff *skb)
> {
> @@ -885,8 +883,14 @@ int __init icmpv6_init(void)
> err = -EAGAIN;
> if (inet6_add_protocol(&icmpv6_protocol, IPPROTO_ICMPV6) < 0)
> goto fail;
> +
> + err = inet6_register_icmp_sender(icmp6_send);
> + if (err)
> + goto sender_reg_err;
> return 0;
>
> +sender_reg_err:
> + inet6_del_protocol(&icmpv6_protocol, IPPROTO_ICMPV6);
> fail:
> pr_err("Failed to register ICMP6 protocol\n");
> unregister_pernet_subsys(&icmpv6_sk_ops);
> @@ -895,6 +899,7 @@ fail:
>
> void icmpv6_cleanup(void)
> {
> + inet6_unregister_icmp_sender(icmp6_send);
> unregister_pernet_subsys(&icmpv6_sk_ops);
> inet6_del_protocol(&icmpv6_protocol, IPPROTO_ICMPV6);
> }
> diff --git a/net/ipv6/ip6_icmp.c b/net/ipv6/ip6_icmp.c
> new file mode 100644
> index 0000000..cfcc563
> --- /dev/null
> +++ b/net/ipv6/ip6_icmp.c
> @@ -0,0 +1,64 @@
> +#include <linux/export.h>
> +#include <linux/icmpv6.h>
> +#include <linux/mutex.h>
> +#include <linux/netdevice.h>
> +#include <linux/spinlock.h>
> +
> +#include <net/ipv6.h>
> +
> +#if IS_ENABLED(CONFIG_IPV6)
> +
> +static ip6_icmp_send_t __rcu *ip6_icmp_send;
> +static DEFINE_MUTEX(handler_lock);
> +
> +int inet6_register_icmp_sender(ip6_icmp_send_t *fn)
> +{
> + int ret = 0;
> +
> + mutex_lock(&handler_lock);
> + if (rcu_dereference(ip6_icmp_send)) {

rcu_dereference_protected()

> + ret = -EBUSY;
> + goto out;
> + }
> + rcu_assign_pointer(ip6_icmp_send, fn);
> +
> +out:
> + mutex_unlock(&handler_lock);
> + return ret;
> +}
> +EXPORT_SYMBOL(inet6_register_icmp_sender);
> +
> +int inet6_unregister_icmp_sender(ip6_icmp_send_t *fn)
> +{
> + int ret = 0;
> +
> + mutex_lock(&handler_lock);
> + if (rcu_dereference(ip6_icmp_send) != fn) {

rcu_dereference_protected()

> + ret = -EINVAL;
> + goto out;
> + }
> + rcu_assign_pointer(ip6_icmp_send, NULL);
> +
> +out:
> + mutex_unlock(&handler_lock);
> + synchronize_net();
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(inet6_unregister_icmp_sender);
> +
> +void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
> +{
> + ip6_icmp_send_t *send;
> +
> + rcu_read_lock();
> + send = rcu_dereference(ip6_icmp_send);
> +
> + if (!send)
> + goto out;
> + send(skb, type, code, info);
> +out:
> + rcu_read_unlock();
> +}
> +EXPORT_SYMBOL(icmpv6_send);
> +#endif