From: Claudio Jeker <cjeker@diehard.n-r-g.com>
Subject: Re: convert bpf interface list into a tailq
To: David Gwynne <david@gwynne.id.au>
Cc: tech@openbsd.org
Date: Tue, 19 Nov 2024 13:27:47 +0100

On Tue, Nov 19, 2024 at 10:17:43PM +1000, David Gwynne wrote:
> at the moment it's a good old hand rolled list.
> 
> we have clean water^W^Wsys/queue.h now, so let's use it. this diff also
> inserts new bpf_ifs at the end of the list instead of the head. this
> means that the list of DLTs per interface will change order, eg, what
> tcpdump -i iwx0 -L prints will change order. currently attachinig
> a bpf descriptor to an interface prefers low numbered DLTs, so this
> doesnt change which one is picked if you run somethinig like tcpdump
> without specifying a dlt.
> 
> ok?

OK claudio@
 
> Index: bpfdesc.h
> ===================================================================
> RCS file: /cvs/src/sys/net/bpfdesc.h,v
> diff -u -p -r1.49 bpfdesc.h
> --- bpfdesc.h	15 Aug 2024 12:20:20 -0000	1.49
> +++ bpfdesc.h	19 Nov 2024 12:07:56 -0000
> @@ -114,7 +114,7 @@ struct bpf_d {
>   * Descriptor associated with each attached hardware interface.
>   */
>  struct bpf_if {
> -	struct bpf_if *bif_next;	/* list of all interfaces */
> +	TAILQ_ENTRY(bpf_if) bif_next;	/* list of all interfaces */
>  	SMR_SLIST_HEAD(, bpf_d) bif_dlist;		/* descriptor list */
>  	struct bpf_if **bif_driverp;	/* pointer into softc */
>  	u_int bif_dlt;			/* link layer type */
> Index: bpf.c
> ===================================================================
> RCS file: /cvs/src/sys/net/bpf.c,v
> diff -u -p -r1.226 bpf.c
> --- bpf.c	17 Nov 2024 12:21:48 -0000	1.226
> +++ bpf.c	19 Nov 2024 12:07:56 -0000
> @@ -98,8 +98,8 @@ int bpf_maxbufsize = BPF_MAXBUFSIZE;	/* 
>   *  bpf_iflist is the list of interfaces; each corresponds to an ifnet
>   *  bpf_d_list is the list of descriptors
>   */
> -struct bpf_if	*bpf_iflist;
> -LIST_HEAD(, bpf_d) bpf_d_list;
> +TAILQ_HEAD(, bpf_if) bpf_iflist = TAILQ_HEAD_INITIALIZER(bpf_iflist);
> +LIST_HEAD(, bpf_d) bpf_d_list = LIST_HEAD_INITIALIZER(bpf_d_list);
>  
>  int	bpf_allocbufs(struct bpf_d *);
>  void	bpf_ifname(struct bpf_if*, struct ifreq *);
> @@ -369,7 +369,6 @@ bpf_detachd(struct bpf_d *d)
>  void
>  bpfilterattach(int n)
>  {
> -	LIST_INIT(&bpf_d_list);
>  }
>  
>  /*
> @@ -1187,7 +1186,7 @@ bpf_setif(struct bpf_d *d, struct ifreq 
>  	/*
>  	 * Look through attached interfaces for the named one.
>  	 */
> -	for (bp = bpf_iflist; bp != NULL; bp = bp->bif_next) {
> +	TAILQ_FOREACH(bp, &bpf_iflist, bif_next) {
>  		if (strcmp(bp->bif_name, ifr->ifr_name) != 0)
>  			continue;
>  
> @@ -1742,8 +1741,7 @@ bpfsattach(caddr_t *bpfp, const char *na
>  	bp->bif_ifp = NULL;
>  	bp->bif_dlt = dlt;
>  
> -	bp->bif_next = bpf_iflist;
> -	bpf_iflist = bp;
> +	TAILQ_INSERT_TAIL(&bpf_iflist, bp, bif_next);
>  
>  	*bp->bif_driverp = NULL;
>  
> @@ -1775,8 +1782,7 @@ bpfdetach(struct ifnet *ifp)
>  
>  	KERNEL_ASSERT_LOCKED();
>  
> -	for (bp = bpf_iflist; bp; bp = nbp) {
> -		nbp = bp->bif_next;
> +	TAILQ_FOREACH_SAFE(bp, &bpf_iflist, bif_next, nbp) {
>  		if (bp->bif_ifp == ifp)
>  			bpfsdetach(bp);
>  	}
> @@ -1786,7 +1792,7 @@ bpfdetach(struct ifnet *ifp)
>  void
>  bpfsdetach(void *p)
>  {
> -	struct bpf_if *bp = p, *tbp;
> +	struct bpf_if *bp = p;
>  	struct bpf_d *bd;
>  	int maj;
>  
> @@ -1804,15 +1810,7 @@ bpfsdetach(void *p)
>  		bpf_put(bd);
>  	}
>  
> -	for (tbp = bpf_iflist; tbp; tbp = tbp->bif_next) {
> -		if (tbp->bif_next == bp) {
> -			tbp->bif_next = bp->bif_next;
> -			break;
> -		}
> -	}
> -
> -	if (bpf_iflist == bp)
> -		bpf_iflist = bp->bif_next;
> +	TAILQ_REMOVE(&bpf_iflist, bp, bif_next);
>  
>  	free(bp, M_DEVBUF, sizeof(*bp));
>  }
> @@ -1865,7 +1863,7 @@ bpf_getdltlist(struct bpf_d *d, struct b
>  	name = d->bd_bif->bif_name;
>  	n = 0;
>  	error = 0;
> -	for (bp = bpf_iflist; bp != NULL; bp = bp->bif_next) {
> +	TAILQ_FOREACH (bp, &bpf_iflist, bif_next) {
>  		if (strcmp(name, bp->bif_name) != 0)
>  			continue;
>  		if (bfl->bfl_list != NULL) {
> @@ -1896,7 +1894,7 @@ bpf_setdlt(struct bpf_d *d, u_int dlt)
>  	if (d->bd_bif->bif_dlt == dlt)
>  		return (0);
>  	name = d->bd_bif->bif_name;
> -	for (bp = bpf_iflist; bp != NULL; bp = bp->bif_next) {
> +	TAILQ_FOREACH (bp, &bpf_iflist, bif_next) {
>  		if (strcmp(name, bp->bif_name) != 0)
>  			continue;
>  		if (bp->bif_dlt == dlt)
> 

-- 
:wq Claudio