From: Alexander Bluhm <bluhm@openbsd.org>
Subject: Re: sysctl(2): unlock `gre_vars'
To: Vitaliy Makkoveev <mvs@openbsd.org>
Cc: tech@openbsd.org
Date: Wed, 4 Dec 2024 18:53:54 +0100

On Wed, Dec 04, 2024 at 08:32:53PM +0300, Vitaliy Makkoveev wrote:
> Both `gre_allow' and `gre_wccp' are atomically accessed integers. They
> could have only '0' and '1' values, so no extra dances around
> atomic_load_int(9) required.

OK bluhm@

> Index: sys/net/if_gre.c
> ===================================================================
> RCS file: /cvs/src/sys/net/if_gre.c,v
> diff -u -p -r1.178 if_gre.c
> --- sys/net/if_gre.c	23 Dec 2023 10:52:54 -0000	1.178
> +++ sys/net/if_gre.c	4 Dec 2024 17:29:28 -0000
> @@ -101,6 +101,11 @@
>  #include <net/if_etherbridge.h>
>  
>  /*
> + * Locks used to protect data:
> + *	a	atomic
> + */
> +
> +/*
>   * packet formats
>   */
>  struct gre_header {
> @@ -545,8 +550,8 @@ struct eoip_tree eoip_tree = RBT_INITIAL
>   * allowed as well.
>   *
>   */
> -int gre_allow = 0;
> -int gre_wccp = 0;
> +int gre_allow = 0;		/* [a] */
> +int gre_wccp = 0;		/* [a] */
>  
>  void
>  greattach(int n)
> @@ -1009,7 +1014,7 @@ gre_input_key(struct mbuf **mp, int *off
>  	int mcast = 0;
>  	uint8_t itos;
>  
> -	if (!gre_allow)
> +	if (!atomic_load_int(&gre_allow))
>  		goto decline;
>  
>  	key->t_rtableid = m->m_pkthdr.ph_rtableid;
> @@ -1092,7 +1097,8 @@ gre_input_key(struct mbuf **mp, int *off
>  		 *     draft-wilson-wrec-wccp-v2-01.txt
>  		 */
>  
> -		if (!gre_wccp && !ISSET(ifp->if_flags, IFF_LINK0))
> +		if (!atomic_load_int(&gre_wccp) &&
> +		    !ISSET(ifp->if_flags, IFF_LINK0))
>  			goto decline;
>  
>  		/*
> @@ -1494,7 +1500,7 @@ gre_output(struct ifnet *ifp, struct mbu
>  	struct m_tag *mtag;
>  	int error = 0;
>  
> -	if (!gre_allow) {
> +	if (!atomic_load_int(&gre_allow)) {
>  		error = EACCES;
>  		goto drop;
>  	}
> @@ -1633,7 +1639,7 @@ mgre_output(struct ifnet *ifp, struct mb
>  	sa_family_t af;
>  	const void *addr;
>  
> -	if (!gre_allow) {
> +	if (!atomic_load_int(&gre_allow)) {
>  		error = EACCES;
>  		goto drop;
>  	}
> @@ -1785,7 +1791,7 @@ egre_start(struct ifnet *ifp)
>  	caddr_t if_bpf;
>  #endif
>  
> -	if (!gre_allow) {
> +	if (!atomic_load_int(&gre_allow)) {
>  		ifq_purge(&ifp->if_snd);
>  		return;
>  	}
> @@ -3642,7 +3648,7 @@ nvgre_start(struct ifnet *ifp)
>  	caddr_t if_bpf;
>  #endif
>  
> -	if (!gre_allow) {
> +	if (!atomic_load_int(&gre_allow)) {
>  		ifq_purge(&ifp->if_snd);
>  		return;
>  	}
> @@ -3833,7 +3839,7 @@ eoip_start(struct ifnet *ifp)
>  	caddr_t if_bpf;
>  #endif
>  
> -	if (!gre_allow) {
> +	if (!atomic_load_int(&gre_allow)) {
>  		ifq_purge(&ifp->if_snd);
>  		return;
>  	}
> @@ -4047,13 +4053,8 @@ int
>  gre_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp, void *newp,
>      size_t newlen)
>  {
> -	int error;
> -
> -	NET_LOCK();
> -	error = sysctl_bounded_arr(gre_vars, nitems(gre_vars), name,
> +	return sysctl_bounded_arr(gre_vars, nitems(gre_vars), name,
>  	    namelen, oldp, oldlenp, newp, newlen);
> -	NET_UNLOCK();
> -	return error;
>  }
>  
>  static inline int
> Index: sys/netinet/in_proto.c
> ===================================================================
> RCS file: /cvs/src/sys/netinet/in_proto.c,v
> diff -u -p -r1.113 in_proto.c
> --- sys/netinet/in_proto.c	22 Aug 2024 10:58:31 -0000	1.113
> +++ sys/netinet/in_proto.c	4 Dec 2024 17:29:28 -0000
> @@ -318,7 +318,7 @@ const struct protosw inetsw[] = {
>    .pr_type	= SOCK_RAW,
>    .pr_domain	= &inetdomain,
>    .pr_protocol	= IPPROTO_GRE,
> -  .pr_flags	= PR_ATOMIC|PR_ADDR|PR_MPSOCKET,
> +  .pr_flags	= PR_ATOMIC|PR_ADDR|PR_MPSOCKET|PR_MPSYSCTL,
>    .pr_input	= gre_input,
>    .pr_ctloutput	= rip_ctloutput,
>    .pr_usrreqs	= &gre_usrreqs,