From 23d2673796e60c7fea6ba218eb084cbd59e7271b Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman@redhat.com>
Date: Mon, 18 Nov 2013 15:39:37 -0800
Subject: [PATCH] linktype: add netlink link/dlt type
With Linux 3.11, we have the possibility to debug local netlink traffic
[1] i.e. the workflow looks like this:
Setup:
modprobe nlmon
ip link add type nlmon
ip link set nlmon0 up
Capture:
tcpdump -i nlmon0 ...
Teardown:
ip link set nlmon0 down
ip link del dev nlmon0
rmmod nlmon
For pcap interoperability, introduce a common link type for netlink
captures.
---
pcap-common.c | 7 ++++++-
pcap-linux.c | 13 +++++++++++++
pcap/bpf.h | 7 ++++++-
3 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/pcap-common.c b/pcap-common.c
index 6175a5a..f26d22e 100644
--- a/pcap-common.c
+++ b/pcap-common.c
@@ -932,7 +932,12 @@
*/
#define LINKTYPE_WIRESHARK_UPPER_PDU 252
-#define LINKTYPE_MATCHING_MAX 252 /* highest value in the "matching" range */
+/*
+ * Link-layer header type for the netlink protocol (nlmon devices).
+ */
+#define LINKTYPE_NETLINK 253
+
+#define LINKTYPE_MATCHING_MAX 253 /* highest value in the "matching" range */
static struct linktype_map {
int dlt;
diff --git a/pcap-linux.c b/pcap-linux.c
index e817382..0651522 100644
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -2972,6 +2972,19 @@ static void map_arphrd_to_dlt(pcap_t *handle, int arptype, int cooked_ok)
handle->linktype = DLT_IEEE802_15_4_NOFCS;
break;
+#ifndef ARPHRD_NETLINK
+#define ARPHRD_NETLINK 824
+#endif
+ case ARPHRD_NETLINK:
+ handle->linktype = DLT_NETLINK;
+ /*
+ * We need to use cooked mode, so that in sll_protocol we
+ * pick up the netlink protocol type such as NETLINK_ROUTE,
+ * NETLINK_GENERIC, NETLINK_FIB_LOOKUP, etc.
+ */
+ handle->cooked = 1;
+ break;
+
default:
handle->linktype = -1;
break;
diff --git a/pcap/bpf.h b/pcap/bpf.h
index ad36eb6..8286ed5 100644
--- a/pcap/bpf.h
+++ b/pcap/bpf.h
@@ -1224,7 +1224,12 @@ struct bpf_program {
*/
#define DLT_WIRESHARK_UPPER_PDU 252
-#define DLT_MATCHING_MAX 252 /* highest value in the "matching" range */
+/*
+ * DLT type for the netlink protocol (nlmon devices).
+ */
+#define DLT_NETLINK 253
+
+#define DLT_MATCHING_MAX 253 /* highest value in the "matching" range */
/*
* DLT and savefile link type values are split into a class and
--
2.4.3