Module Name: src
Committed By: ozaki-r
Date: Wed Nov 30 06:02:37 UTC 2022
Modified Files:
src/sys/net: bpf.c
Log Message:
bpf: support sending packets on loopback interfaces
Previously sending packets on a loopback interface via bpf failed
because the packets are treated as AF_UNSPEC by bpf and the loopback
interface couldn't handle such packets.
This fix enables user programs to prepend a protocol family (AF_INET or
AF_INET6) to a payload. bpf interprets it and treats a packet as so,
not just AF_UNSPEC. The protocol family is encoded as 4 bytes, host byte
order as per DLT_NULL in the specification(*).
(*) https://www.tcpdump.org/linktypes.html
Proposed on tech-net and tech-kern
To generate a diff of this commit:
cvs rdiff -u -r1.248 -r1.249 src/sys/net/bpf.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/net/bpf.c
diff -u src/sys/net/bpf.c:1.248 src/sys/net/bpf.c:1.249
--- src/sys/net/bpf.c:1.248 Sat Nov 19 08:53:06 2022
+++ src/sys/net/bpf.c Wed Nov 30 06:02:37 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: bpf.c,v 1.248 2022/11/19 08:53:06 yamt Exp $ */
+/* $NetBSD: bpf.c,v 1.249 2022/11/30 06:02:37 ozaki-r Exp $ */
/*
* Copyright (c) 1990, 1991, 1993
@@ -39,7 +39,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bpf.c,v 1.248 2022/11/19 08:53:06 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bpf.c,v 1.249 2022/11/30 06:02:37 ozaki-r Exp $");
#if defined(_KERNEL_OPT)
#include "opt_bpf.h"
@@ -89,6 +89,7 @@ __KERNEL_RCSID(0, "$NetBSD: bpf.c,v 1.24
#include <net/if_arc.h>
#include <net/if_ether.h>
+#include <net/if_types.h>
#include <netinet/in.h>
#include <netinet/if_inarp.h>
@@ -244,7 +245,7 @@ static void bpf_freed(struct bpf_d *);
static void bpf_free_filter(struct bpf_filter *);
static void bpf_ifname(struct ifnet *, struct ifreq *);
static void *bpf_mcpy(void *, const void *, size_t);
-static int bpf_movein(struct uio *, int, uint64_t,
+static int bpf_movein(struct ifnet *, struct uio *, int, uint64_t,
struct mbuf **, struct sockaddr *,
struct bpf_filter **);
static void bpf_attachd(struct bpf_d *, struct bpf_if *);
@@ -323,7 +324,7 @@ bpf_jit_freecode(bpfjit_func_t jcode)
}
static int
-bpf_movein(struct uio *uio, int linktype, uint64_t mtu, struct mbuf **mp,
+bpf_movein(struct ifnet *ifp, struct uio *uio, int linktype, uint64_t mtu, struct mbuf **mp,
struct sockaddr *sockp, struct bpf_filter **wfilter)
{
struct mbuf *m, *m0, *n;
@@ -385,7 +386,11 @@ bpf_movein(struct uio *uio, int linktype
case DLT_NULL:
sockp->sa_family = AF_UNSPEC;
- hlen = 0;
+ if (ifp->if_type == IFT_LOOP) {
+ /* Set here to apply the following validations */
+ hlen = sizeof(uint32_t);
+ } else
+ hlen = 0;
align = 0;
break;
@@ -441,8 +446,15 @@ bpf_movein(struct uio *uio, int linktype
}
if (hlen != 0) {
- /* move link level header in the top of mbuf to sa_data */
- memcpy(sockp->sa_data, mtod(m0, void *), hlen);
+ if (linktype == DLT_NULL && ifp->if_type == IFT_LOOP) {
+ uint32_t af;
+ /* the link header indicates the address family */
+ memcpy(&af, mtod(m0, void *), sizeof(af));
+ sockp->sa_family = af;
+ } else {
+ /* move link level header in the top of mbuf to sa_data */
+ memcpy(sockp->sa_data, mtod(m0, void *), hlen);
+ }
m0->m_data += hlen;
m0->m_len -= hlen;
}
@@ -853,7 +865,7 @@ bpf_write(struct file *fp, off_t *offp,
goto out;
}
- error = bpf_movein(uio, (int)bp->bif_dlt, ifp->if_mtu, &m,
+ error = bpf_movein(ifp, uio, (int)bp->bif_dlt, ifp->if_mtu, &m,
(struct sockaddr *) &dst, &d->bd_wfilter);
if (error)
goto out;
