From: Vitaliy Makkoveev <otto@bsdbox.dev>
Subject: Re: const sockaddr in tcp syn cache
To: Alexander Bluhm <alexander.bluhm@gmx.net>
Cc: tech@openbsd.org
Date: Sat, 27 Jan 2024 03:37:28 +0300

> On 25 Jan 2024, at 02:47, Alexander Bluhm <alexander.bluhm@gmx.net> wrote:
> 
> On Fri, Jan 19, 2024 at 03:01:12PM +0100, Alexander Bluhm wrote:
>> On Fri, Jan 19, 2024 at 02:47:53PM +0100, Alexander Bluhm wrote:
>>> tcp6_ctlinput() casts a constant sockaddr_sin6 to non-const sockaddr.
>>> sa6_src may be &sa6_any which lives in read-only data section.
>>> 
>>> Better pass down the const addresses to tcp syn cache.  We only need
>>> them for lookup.
>> 
>> Oops, missed one satosin_const which breaks non-INET6 builds.
>> 
>> updated diff, ok?
> 
> anyone?
> 

ok mvs

>> Index: netinet/tcp_input.c
>> ===================================================================
>> RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_input.c,v
>> diff -u -p -r1.398 tcp_input.c
>> --- netinet/tcp_input.c	11 Jan 2024 13:49:49 -0000	1.398
>> +++ netinet/tcp_input.c	19 Jan 2024 13:56:41 -0000
>> @@ -201,8 +201,8 @@ int	 syn_cache_add(struct sockaddr *, st
>> struct socket *syn_cache_get(struct sockaddr *, struct sockaddr *,
>> 		struct tcphdr *, unsigned int, unsigned int, struct socket *,
>> 		struct mbuf *, uint64_t);
>> -struct syn_cache *syn_cache_lookup(struct sockaddr *, struct sockaddr *,
>> -		struct syn_cache_head **, u_int);
>> +struct syn_cache *syn_cache_lookup(const struct sockaddr *,
>> +		const struct sockaddr *, struct syn_cache_head **, u_int);
>> 
>> /*
>>  * Insert segment ti into reassembly queue of tcp with
>> @@ -3109,9 +3109,9 @@ struct mutex syn_cache_mtx = MUTEX_INITI
>> #ifndef INET6
>> #define	SYN_HASHALL(hash, src, dst, rand) \
>> do {									\
>> -	hash = SYN_HASH(&satosin(src)->sin_addr,			\
>> -		satosin(src)->sin_port,					\
>> -		satosin(dst)->sin_port, (rand));			\
>> +	hash = SYN_HASH(&satosin_const(src)->sin_addr,			\
>> +		satosin_const(src)->sin_port,				\
>> +		satosin_const(dst)->sin_port, (rand));			\
>> } while (/*CONSTCOND*/ 0)
>> #else
>> #define SYN_HASH6(sa, sp, dp, rand) \
>> @@ -3125,14 +3125,14 @@ do {									\
>> do {									\
>> 	switch ((src)->sa_family) {					\
>> 	case AF_INET:							\
>> -		hash = SYN_HASH(&satosin(src)->sin_addr,		\
>> -			satosin(src)->sin_port,				\
>> -			satosin(dst)->sin_port, (rand));		\
>> +		hash = SYN_HASH(&satosin_const(src)->sin_addr,		\
>> +			satosin_const(src)->sin_port,			\
>> +			satosin_const(dst)->sin_port, (rand));		\
>> 		break;							\
>> 	case AF_INET6:							\
>> -		hash = SYN_HASH6(&satosin6(src)->sin6_addr,		\
>> -			satosin6(src)->sin6_port,			\
>> -			satosin6(dst)->sin6_port, (rand));		\
>> +		hash = SYN_HASH6(&satosin6_const(src)->sin6_addr,	\
>> +			satosin6_const(src)->sin6_port,			\
>> +			satosin6_const(dst)->sin6_port, (rand));	\
>> 		break;							\
>> 	default:							\
>> 		hash = 0;						\
>> @@ -3423,7 +3423,7 @@ syn_cache_cleanup(struct tcpcb *tp)
>>  * Find an entry in the syn cache.
>>  */
>> struct syn_cache *
>> -syn_cache_lookup(struct sockaddr *src, struct sockaddr *dst,
>> +syn_cache_lookup(const struct sockaddr *src, const struct sockaddr *dst,
>>     struct syn_cache_head **headp, u_int rtableid)
>> {
>> 	struct syn_cache_set *sets[2];
>> @@ -3709,8 +3709,8 @@ syn_cache_reset(struct sockaddr *src, st
>> }
>> 
>> void
>> -syn_cache_unreach(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th,
>> -    u_int rtableid)
>> +syn_cache_unreach(const struct sockaddr *src, const struct sockaddr *dst,
>> +    struct tcphdr *th, u_int rtableid)
>> {
>> 	struct syn_cache *sc;
>> 	struct syn_cache_head *scp;
>> Index: netinet/tcp_subr.c
>> ===================================================================
>> RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_subr.c,v
>> diff -u -p -r1.195 tcp_subr.c
>> --- netinet/tcp_subr.c	11 Jan 2024 13:49:49 -0000	1.195
>> +++ netinet/tcp_subr.c	19 Jan 2024 13:37:29 -0000
>> @@ -698,8 +698,8 @@ tcp6_ctlinput(int cmd, struct sockaddr *
>> 		} else if (inet6ctlerrmap[cmd] == EHOSTUNREACH ||
>> 		    inet6ctlerrmap[cmd] == ENETUNREACH ||
>> 		    inet6ctlerrmap[cmd] == EHOSTDOWN)
>> -			syn_cache_unreach((struct sockaddr *)sa6_src,
>> -			    sa, &th, rdomain);
>> +			syn_cache_unreach(sin6tosa_const(sa6_src), sa, &th,
>> +			    rdomain);
>> 		in_pcbunref(inp);
>> 	} else {
>> 		in6_pcbnotify(&tcbtable, sa6, 0,
>> Index: netinet/tcp_var.h
>> ===================================================================
>> RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_var.h,v
>> diff -u -p -r1.174 tcp_var.h
>> --- netinet/tcp_var.h	11 Jan 2024 13:49:49 -0000	1.174
>> +++ netinet/tcp_var.h	19 Jan 2024 13:37:29 -0000
>> @@ -799,7 +799,7 @@ int	tcp_signature(struct tdb *, int, str
>> #endif /* TCP_SIGNATURE */
>> void     tcp_set_iss_tsm(struct tcpcb *);
>> 
>> -void	 syn_cache_unreach(struct sockaddr *, struct sockaddr *,
>> +void	 syn_cache_unreach(const struct sockaddr *, const struct sockaddr *,
>> 	   struct tcphdr *, u_int);
>> void	 syn_cache_init(void);
>> void	 syn_cache_cleanup(struct tcpcb *);
>> Index: netinet6/in6.h
>> ===================================================================
>> RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/in6.h,v
>> diff -u -p -r1.111 in6.h
>> --- netinet6/in6.h	28 Nov 2023 13:23:20 -0000	1.111
>> +++ netinet6/in6.h	19 Jan 2024 13:37:29 -0000
>> @@ -459,6 +459,12 @@ sin6tosa(struct sockaddr_in6 *sin6)
>> 	return ((struct sockaddr *)(sin6));
>> }
>> 
>> +static inline const struct sockaddr *
>> +sin6tosa_const(const struct sockaddr_in6 *sin6)
>> +{
>> +	return ((const struct sockaddr *)(sin6));
>> +}
>> +
>> static inline struct in6_ifaddr *
>> ifatoia6(struct ifaddr *ifa)
>> {
>