Prepare bpf_sysctl() for upcoming net_sysctl() unlocking.

Both NET_BPF_MAXBUFSIZE and NET_BPF_BUFSIZE (`bpf_maxbufsize' and
`bpf_bufsize' respectively) are atomically accessed integers. No locks
required to modify them.

ok bluhm

diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index 6adc594..b7c2f1b 100644 (file)
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: bpf.c,v 1.223 2024/08/05 23:56:10 dlg Exp $   */
+/*     $OpenBSD: bpf.c,v 1.224 2024/08/12 17:02:58 mvs Exp $   */
 /*     $NetBSD: bpf.c,v 1.33 1997/02/21 23:59:35 thorpej Exp $ */
 
 /*
@@ -83,11 +83,16 @@
 
 #define PRINET  26                     /* interruptible */
 
+/*
+ * Locks used to protect data:
+ *     a       atomic
+ */
+
 /*
  * The default read buffer size is patchable.
  */
-int bpf_bufsize = BPF_BUFSIZE;
-int bpf_maxbufsize = BPF_MAXBUFSIZE;
+int bpf_bufsize = BPF_BUFSIZE;         /* [a] */
+int bpf_maxbufsize = BPF_MAXBUFSIZE;   /* [a] */
 
 /*
  *  bpf_iflist is the list of interfaces; each corresponds to an ifnet
@@ -117,8 +122,6 @@ int filt_bpfread(struct knote *, long);
 int    filt_bpfreadmodify(struct kevent *, struct knote *);
 int    filt_bpfreadprocess(struct knote *, struct kevent *);
 
-int    bpf_sysctl_locked(int *, u_int, void *, size_t *, void *, size_t);
-
 struct bpf_d *bpfilter_lookup(int);
 
 /*
@@ -137,9 +140,6 @@ void        bpf_d_smr(void *);
 void   bpf_get(struct bpf_d *);
 void   bpf_put(struct bpf_d *);
 
-
-struct rwlock bpf_sysctl_lk = RWLOCK_INITIALIZER("bpfsz");
-
 int
 bpf_movein(struct uio *uio, struct bpf_d *d, struct mbuf **mp,
     struct sockaddr *sockp)
@@ -393,7 +393,7 @@ bpfopen(dev_t dev, int flag, int mode, struct proc *p)
 
        /* Mark "free" and do most initialization. */
        bd->bd_unit = unit;
-       bd->bd_bufsize = bpf_bufsize;
+       bd->bd_bufsize = atomic_load_int(&bpf_bufsize);
        bd->bd_sig = SIGIO;
        mtx_init(&bd->bd_mtx, IPL_NET);
        task_set(&bd->bd_wake_task, bpf_wakeup_cb, bd);
@@ -853,9 +853,11 @@ bpfioctl(dev_t dev, u_long cmd, caddr_t addr, int flag, struct proc *p)
                        error = EINVAL;
                else {
                        u_int size = *(u_int *)addr;
+                       int bpf_maxbufsize_local =
+                           atomic_load_int(&bpf_maxbufsize);
 
-                       if (size > bpf_maxbufsize)
-                               *(u_int *)addr = size = bpf_maxbufsize;
+                       if (size > bpf_maxbufsize_local)
+                               *(u_int *)addr = size = bpf_maxbufsize_local;
                        else if (size < BPF_MINBUFSIZE)
                                *(u_int *)addr = size = BPF_MINBUFSIZE;
                        mtx_enter(&d->bd_mtx);
@@ -1815,42 +1817,25 @@ bpfsdetach(void *p)
 }
 
 int
-bpf_sysctl_locked(int *name, u_int namelen, void *oldp, size_t *oldlenp,
-    void *newp, size_t newlen)
+bpf_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp, void *newp,
+    size_t newlen)
 {
+       if (namelen != 1)
+               return (ENOTDIR);
+
        switch (name[0]) {
        case NET_BPF_BUFSIZE:
                return sysctl_int_bounded(oldp, oldlenp, newp, newlen,
-                   &bpf_bufsize, BPF_MINBUFSIZE, bpf_maxbufsize);
+                   &bpf_bufsize, BPF_MINBUFSIZE,
+                   atomic_load_int(&bpf_maxbufsize));
        case NET_BPF_MAXBUFSIZE:
                return sysctl_int_bounded(oldp, oldlenp, newp, newlen,
                    &bpf_maxbufsize, BPF_MINBUFSIZE, INT_MAX);
        default:
                return (EOPNOTSUPP);
        }
-}
-
-int
-bpf_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp, void *newp,
-    size_t newlen)
-{
-       int flags = RW_INTR;
-       int error;
 
-       if (namelen != 1)
-               return (ENOTDIR);
-
-       flags |= (newp == NULL) ? RW_READ : RW_WRITE;
-
-       error = rw_enter(&bpf_sysctl_lk, flags);
-       if (error != 0)
-               return (error);
-
-       error = bpf_sysctl_locked(name, namelen, oldp, oldlenp, newp, newlen);
-
-       rw_exit(&bpf_sysctl_lk);
-
-       return (error);
+       /* NOTREACHED */
 }
 
 struct bpf_d *