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From: David Gibson <david@gibson.dropbear.id.au>
To: Stefano Brivio <sbrivio@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH 05/32] tcp: Better helpers for converting between connection pointer and index
Date: Thu, 17 Nov 2022 12:24:59 +1100	[thread overview]
Message-ID: <Y3WNa+gm9bni6zg7@yekko> (raw)
In-Reply-To: <20221117001130.247743ea@elisabeth>

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On Thu, Nov 17, 2022 at 12:11:30AM +0100, Stefano Brivio wrote:
> On Wed, 16 Nov 2022 15:41:45 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > The macro CONN_OR_NULL() is used to look up connections by index with
> > bounds checking.  Replace it with an inline function, which means:
> >     - Better type checking
> >     - No danger of multiple evaluation of an @index with side effects
> > 
> > Also add a helper to perform the reverse translation: from connection
> > pointer to index.  Introduce a macro for this which will make later
> > cleanups easier and safer.
> 
> Ah, yes, much better, agreed. Just two things here:
> 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  tcp.c | 83 ++++++++++++++++++++++++++++++++---------------------------
> >  1 file changed, 45 insertions(+), 38 deletions(-)
> > 
> > diff --git a/tcp.c b/tcp.c
> > index d043123..4e56a6c 100644
> > --- a/tcp.c
> > +++ b/tcp.c
> > @@ -518,14 +518,6 @@ struct tcp_conn {
> >  	 (conn->events & (SOCK_FIN_RCVD | TAP_FIN_RCVD)))
> >  #define CONN_HAS(conn, set)	((conn->events & (set)) == (set))
> >  
> > -#define CONN(index)		(tc + (index))
> > -
> > -/* We probably don't want to use gcc statement expressions (for portability), so
> > - * use this only after well-defined sequence points (no pre-/post-increments).
> > - */
> > -#define CONN_OR_NULL(index)						\
> > -	(((int)(index) >= 0 && (index) < TCP_MAX_CONNS) ? (tc + (index)) : NULL)
> > -
> >  static const char *tcp_event_str[] __attribute((__unused__)) = {
> >  	"SOCK_ACCEPTED", "TAP_SYN_RCVD", "ESTABLISHED", "TAP_SYN_ACK_SENT",
> >  
> > @@ -705,6 +697,21 @@ static size_t tcp6_l2_flags_buf_bytes;
> >  /* TCP connections */
> >  static struct tcp_conn tc[TCP_MAX_CONNS];
> >  
> > +#define CONN(index)		(tc + (index))
> > +#define CONN_IDX(conn)		((conn) - tc)
> > +
> > +/** conn_at_idx() - Find a connection by index, if present
> > + * @index:	Index of connection to lookup
> > + *
> > + * Return:	Pointer to connection, or NULL if @index is out of bounds
> 
> Return: pointer [...]

Fixed.

> > + */
> > +static inline struct tcp_conn *conn_at_idx(int index)
> 
> The CONN_OR_NULL name made it very explicit that the pointer obtained
> there could be NULL. On the other hand I find conn_at_idx() more
> descriptive. But maybe conn_or_null() would be "safer". I don't really
> have a preference.

I see your point, but on balance I think I marginally prefer
conn_at_idx(), so I've left it.

-- 
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

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  reply	other threads:[~2022-11-17  2:08 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-16  4:41 [PATCH 00/32] Use dual stack sockets to listen for inbound TCP connections David Gibson
2022-11-16  4:41 ` [PATCH 01/32] clang-tidy: Suppress warning about assignments in if statements David Gibson
2022-11-16 23:10   ` Stefano Brivio
2022-11-17  1:20     ` David Gibson
2022-11-16  4:41 ` [PATCH 02/32] style: Minor corrections to function comments David Gibson
2022-11-16 23:11   ` Stefano Brivio
2022-11-17  1:21     ` David Gibson
2022-11-16  4:41 ` [PATCH 03/32] tcp_splice: #include tcp_splice.h in tcp_splice.c David Gibson
2022-11-16  4:41 ` [PATCH 04/32] tcp: Remove unused TCP_MAX_SOCKS constant David Gibson
2022-11-16  4:41 ` [PATCH 05/32] tcp: Better helpers for converting between connection pointer and index David Gibson
2022-11-16 23:11   ` Stefano Brivio
2022-11-17  1:24     ` David Gibson [this message]
2022-11-16  4:41 ` [PATCH 06/32] tcp_splice: Helpers for converting from index to/from tcp_splice_conn David Gibson
2022-11-16  4:41 ` [PATCH 07/32] tcp: Move connection state structures into a shared header David Gibson
2022-11-16  4:41 ` [PATCH 08/32] tcp: Add connection union type David Gibson
2022-11-16  4:41 ` [PATCH 09/32] tcp: Improved helpers to update connections after moving David Gibson
2022-11-16  4:41 ` [PATCH 10/32] tcp: Unify spliced and non-spliced connection tables David Gibson
2022-11-16  4:41 ` [PATCH 11/32] tcp: Unify tcp_defer_handler and tcp_splice_defer_handler() David Gibson
2022-11-16  4:41 ` [PATCH 12/32] tcp: Partially unify tcp_timer() and tcp_splice_timer() David Gibson
2022-11-16  4:41 ` [PATCH 13/32] tcp: Unify the IN_EPOLL flag David Gibson
2022-11-16  4:41 ` [PATCH 14/32] tcp: Separate helpers to create ns listening sockets David Gibson
2022-11-16 23:51   ` Stefano Brivio
2022-11-17  1:32     ` David Gibson
2022-11-16  4:41 ` [PATCH 15/32] tcp: Unify part of spliced and non-spliced conn_from_sock path David Gibson
2022-11-16 23:53   ` Stefano Brivio
2022-11-17  1:37     ` David Gibson
2022-11-17  7:30       ` Stefano Brivio
2022-11-17  8:58         ` David Gibson
2022-11-16  4:41 ` [PATCH 16/32] tcp: Use the same sockets to listen for spliced and non-spliced connections David Gibson
2022-11-16 23:54   ` Stefano Brivio
2022-11-17  1:43     ` David Gibson
2022-11-16  4:41 ` [PATCH 17/32] tcp: Remove splice from tcp_epoll_ref David Gibson
2022-11-16  4:41 ` [PATCH 18/32] tcp: Don't store hash bucket in connection structures David Gibson
2022-11-16  4:41 ` [PATCH 19/32] inany: Helper functions for handling addresses which could be IPv4 or IPv6 David Gibson
2022-11-16 23:54   ` Stefano Brivio
2022-11-17  1:48     ` David Gibson
2022-11-16  4:42 ` [PATCH 20/32] tcp: Hash IPv4 and IPv4-mapped-IPv6 addresses the same David Gibson
2022-11-16  4:42 ` [PATCH 21/32] tcp: Take tcp_hash_insert() address from struct tcp_conn David Gibson
2022-11-16  4:42 ` [PATCH 22/32] tcp: Simplify tcp_hash_match() to take an inany_addr David Gibson
2022-11-16  4:42 ` [PATCH 23/32] tcp: Unify initial sequence number calculation for IPv4 and IPv6 David Gibson
2022-11-16  4:42 ` [PATCH 24/32] tcp: Have tcp_seq_init() take its parameters from struct tcp_conn David Gibson
2022-11-16  4:42 ` [PATCH 25/32] tcp: Fix small errors in tcp_seq_init() time handling David Gibson
2022-11-16  4:42 ` [PATCH 26/32] tcp: Remove v6 flag from tcp_epoll_ref David Gibson
2022-11-17  0:15   ` Stefano Brivio
2022-11-17  1:50     ` David Gibson
2022-11-16  4:42 ` [PATCH 27/32] tcp: NAT IPv4-mapped IPv6 addresses like IPv4 addresses David Gibson
2022-11-17  0:15   ` Stefano Brivio
2022-11-17  2:00     ` David Gibson
2022-11-16  4:42 ` [PATCH 28/32] tcp_splice: Allow splicing of connections from IPv4-mapped loopback David Gibson
2022-11-17  0:15   ` Stefano Brivio
2022-11-17  2:05     ` David Gibson
2022-11-16  4:42 ` [PATCH 29/32] tcp: Consolidate tcp_sock_init[46] David Gibson
2022-11-16  4:42 ` [PATCH 30/32] util: Allow sock_l4() to open dual stack sockets David Gibson
2022-11-16  4:42 ` [PATCH 31/32] util: Always return -1 on error in sock_l4() David Gibson
2022-11-16  4:42 ` [PATCH 32/32] tcp: Use dual stack sockets for port forwarding when possible David Gibson
2022-11-17  0:15   ` Stefano Brivio
2022-11-17  2:08     ` David Gibson

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