Re: [PATCH 19/32] inany: Helper functions for handling addresses which could be IPv4 or IPv6

[David Gibson <david@gibson.dropbear.id.au>]

[-- Attachment #1: Type: text/plain, Size: 7910 bytes --]

On Thu, Nov 17, 2022 at 12:54:08AM +0100, Stefano Brivio wrote:
> [Reviewed until 25/32 so far]
> 
> On Wed, 16 Nov 2022 15:41:59 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > struct tcp_conn stores an address which could be IPv6 or IPv4 using a
> > union.  We can do this without an additional tag by encoding IPv4 addresses
> > as IPv4-mapped IPv6 addresses.
> > 
> > This approach is useful wider than the specific place in tcp_conn, so
> > expose a new 'union inany_addr' like this from a new inany.h.  Along with
> > that create a number of helper functions to make working with these "inany"
> > addresses easier.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  Makefile     |  6 ++--
> >  inany.h      | 68 ++++++++++++++++++++++++++++++++++++++++
> >  tcp.c        | 88 +++++++++++++++++++++++++---------------------------
> >  tcp_conn.h   | 15 ++-------
> >  tcp_splice.c |  1 +
> >  5 files changed, 117 insertions(+), 61 deletions(-)
> >  create mode 100644 inany.h
> > 
> > diff --git a/Makefile b/Makefile
> > index 9046b0b..ca453aa 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -44,9 +44,9 @@ SRCS = $(PASST_SRCS) $(QRAP_SRCS)
> >  MANPAGES = passt.1 pasta.1 qrap.1
> >  
> >  PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h icmp.h \
> > -	isolation.h lineread.h log.h ndp.h netlink.h packet.h passt.h pasta.h \
> > -	pcap.h port_fwd.h siphash.h tap.h tcp.h tcp_conn.h tcp_splice.h udp.h \
> > -	util.h
> > +	inany.h isolation.h lineread.h log.h ndp.h netlink.h packet.h passt.h \
> > +	pasta.h pcap.h port_fwd.h siphash.h tap.h tcp.h tcp_conn.h \
> > +	tcp_splice.h udp.h util.h
> >  HEADERS = $(PASST_HEADERS) seccomp.h
> >  
> >  # On gcc 11 and 12, with -O2 and -flto, tcp_hash() and siphash_20b(), if
> > diff --git a/inany.h b/inany.h
> > new file mode 100644
> > index 0000000..4e53da9
> > --- /dev/null
> > +++ b/inany.h
> > @@ -0,0 +1,68 @@
> > +/* SPDX-License-Identifier: AGPL-3.0-or-later
> > + * Copyright Red Hat
> > + * Author: David Gibson <david@gibson.dropbear.id.au>
> > + *
> > + * inany.h - Types and helpers for handling addresses which could be
> > + *           IPv6 or IPv4 (encoded as IPv4-mapped IPv6 addresses)
> > + */
> > +
> > +#include <assert.h>
> > +
> > +/** union inany_addr - Represents either an IPv4 or IPv6 address
> > + * @a6:		Address as an IPv6 address, may be IPv4-mapped
> > + * @_v4._zero:	All zero-bits for an IPv4 address
> > + * @_v4._one:	All one-bits for an IPv4 address
> > + * @_v4.a4:	If @a6 is an IPv4 mapped address, this is the raw IPv4 address
> > + *
> > + * Fields starting with _ shouldn't be accessed except via helpers.
> > + */
> > +union inany_addr {
> > +	struct in6_addr a6;
> > +	struct {
> > +		uint8_t _zero[10];
> > +		uint8_t _one[2];
> > +		struct in_addr a4;
> > +	} _v4mapped;
> 
> I'm not sure the extra _ are really worth it. I mean, that's not really
> enforceable, so saying that v4mapped should only be accessed by helpers
> should be equivalent.

Fair call.  Adjusted.

> 
> > +};
> > +
> > +/** inany_v4 - Extract IPv4 address, if present, from IPv[46] address
> > + * @addr:	IPv4 or IPv6 address
> > + *
> > + * Return: IPv4 address if @addr is IPv4, NULL otherwise
> > + */
> > +static inline const struct in_addr *inany_v4(const union inany_addr *addr)
> > +{
> > +	if (!IN6_IS_ADDR_V4MAPPED(&addr->a6))
> > +		return NULL;
> > +	return &addr->_v4mapped.a4;
> > +}
> > +
> > +/** inany_equals - Compare two IPv[46] addresses
> > + * @a, @b:	IPv[46] addresses
> > + *
> > + * Return: true if @a and @b are the same address
> > + */
> > +static inline bool inany_equals(const union inany_addr *a,
> > +				const union inany_addr *b)
> > +{
> > +	return IN6_ARE_ADDR_EQUAL(&a->a6, &b->a6);
> > +}
> > +
> > +/** inany_from_af - Set IPv[46] address from IPv4 or IPv6 address
> > + * @aa:		Pointer to store IPv[46] address
> > + * @af:		Address family of @addr
> > + * @addr:	struct in_addr (IPv4) or struct in6_addr (IPv6)
> > + */
> > +static inline void inany_from_af(union inany_addr *aa, int af, const void *addr)
> > +{
> > +	if (af == AF_INET6) {
> > +		aa->a6 = *((struct in6_addr *)addr);
> > +	} else if (af == AF_INET) {
> > +		memset(&aa->_v4mapped._zero, 0, sizeof(aa->_v4mapped._zero));
> > +		memset(&aa->_v4mapped._one, 0xff, sizeof(aa->_v4mapped._one));
> > +		aa->_v4mapped.a4 = *((struct in_addr *)addr);
> > +	} else {
> > +		/* Not valid to call with other address families */
> > +		assert(0);
> > +	}
> > +}
> > diff --git a/tcp.c b/tcp.c
> > index 7686766..4040198 100644
> > --- a/tcp.c
> > +++ b/tcp.c
> > @@ -301,6 +301,7 @@
> >  #include "conf.h"
> >  #include "tcp_splice.h"
> >  #include "log.h"
> > +#include "inany.h"
> >  
> >  #include "tcp_conn.h"
> >  
> > @@ -404,7 +405,7 @@ struct tcp6_l2_head {	/* For MSS6 macro: keep in sync with tcp6_l2_buf_t */
> >  #define OPT_SACK	5
> >  #define OPT_TS		8
> >  
> > -#define CONN_V4(conn)		IN6_IS_ADDR_V4MAPPED(&conn->a.a6)
> > +#define CONN_V4(conn)		(!!inany_v4(&(conn)->addr))
> >  #define CONN_V6(conn)		(!CONN_V4(conn))
> >  #define CONN_IS_CLOSING(conn)						\
> >  	((conn->events & ESTABLISHED) &&				\
> > @@ -438,7 +439,7 @@ static int tcp_sock_init_ext	[NUM_PORTS][IP_VERSIONS];
> >  static int tcp_sock_ns		[NUM_PORTS][IP_VERSIONS];
> >  
> >  /* Table of destinations with very low RTT (assumed to be local), LRU */
> > -static struct in6_addr low_rtt_dst[LOW_RTT_TABLE_SIZE];
> > +static union inany_addr low_rtt_dst[LOW_RTT_TABLE_SIZE];
> >  
> >  /* Static buffers */
> >  
> > @@ -861,7 +862,7 @@ static int tcp_rtt_dst_low(const struct tcp_tap_conn *conn)
> >  	int i;
> >  
> >  	for (i = 0; i < LOW_RTT_TABLE_SIZE; i++)
> > -		if (IN6_ARE_ADDR_EQUAL(&conn->a.a6, low_rtt_dst + i))
> > +		if (inany_equals(&conn->addr, low_rtt_dst + i))
> >  			return 1;
> >  
> >  	return 0;
> > @@ -883,7 +884,7 @@ static void tcp_rtt_dst_check(const struct tcp_tap_conn *conn,
> >  		return;
> >  
> >  	for (i = 0; i < LOW_RTT_TABLE_SIZE; i++) {
> > -		if (IN6_ARE_ADDR_EQUAL(&conn->a.a6, low_rtt_dst + i))
> > +		if (inany_equals(&conn->addr, low_rtt_dst + i))
> >  			return;
> >  		if (hole == -1 && IN6_IS_ADDR_UNSPECIFIED(low_rtt_dst + i))
> >  			hole = i;
> > @@ -895,10 +896,10 @@ static void tcp_rtt_dst_check(const struct tcp_tap_conn *conn,
> >  	if (hole == -1)
> >  		return;
> >  
> > -	memcpy(low_rtt_dst + hole++, &conn->a.a6, sizeof(conn->a.a6));
> > +	low_rtt_dst[hole++] = conn->addr;
> >  	if (hole == LOW_RTT_TABLE_SIZE)
> >  		hole = 0;
> > -	memcpy(low_rtt_dst + hole, &in6addr_any, sizeof(conn->a.a6));
> > +	inany_from_af(low_rtt_dst + hole, AF_INET6, &in6addr_any);
> >  #else
> >  	(void)conn;
> >  	(void)tinfo;
> > @@ -1187,13 +1188,14 @@ static int tcp_hash_match(const struct tcp_tap_conn *conn,
> >  			  int af, const void *addr,
> >  			  in_port_t tap_port, in_port_t sock_port)
> >  {
> > -	if (af == AF_INET && CONN_V4(conn)			&&
> > -	    !memcmp(&conn->a.a4.a, addr, sizeof(conn->a.a4.a))	&&
> > +	const struct in_addr *a4 = inany_v4(&conn->addr);
> > +
> > +	if (af == AF_INET && a4	&& !memcmp(a4, addr, sizeof(*a4)) &&
> >  	    conn->tap_port == tap_port && conn->sock_port == sock_port)
> >  		return 1;
> >  
> >  	if (af == AF_INET6					&&
> > -	    IN6_ARE_ADDR_EQUAL(&conn->a.a6, addr)		&&
> > +	    IN6_ARE_ADDR_EQUAL(&conn->addr.a6, addr)		&&
> >  	    conn->tap_port == tap_port && conn->sock_port == sock_port)
> >  		return 1;
> 
> Note to self or other reviewers: switch to inany_equals() in 22/32.
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]