extensions: libxt_bpf: support ebpf pinned objects

Exercise the new kernel feature introduced in commit 2c16d6033264
("netfilter: xt_bpf: support ebpf") to load pinned eBPF programs.

The new interface allows instantiating a bpf match using

  -m bpf --object-pinned ${PATH}

where ${PATH} points to a node in a bpf virtual filesystem. See
also the revised man page.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 16 insertions, 3 deletions

diff --git a/extensions/libxt_bpf.man b/extensions/libxt_bpf.man
index 302e0103..1d2aa9e6 100644
--- a/extensions/libxt_bpf.man
+++ b/extensions/libxt_bpf.man
@@ -1,8 +1,21 @@
-Match using Linux Socket Filter. Expects a BPF program in decimal format. This
-is the format generated by the \fBnfbpf_compile\fP utility.
+Match using Linux Socket Filter. Expects a path to an eBPF object or a cBPF
+program in decimal format.
+.TP
+\fB\-\-object\-pinned\fP \fIpath\fP
+Pass a path to a pinned eBPF object.
+.PP
+Applications load eBPF programs into the kernel with the bpf() system call and
+BPF_PROG_LOAD command and can pin them in a virtual filesystem with BPF_OBJ_PIN.
+To use a pinned object in iptables, mount the bpf filesystem using
+.IP
+mount \-t bpf bpf ${BPF_MOUNT}
+.PP
+then insert the filter in iptables by path:
+.IP
+iptables \-A OUTPUT \-m bpf \-\-object\-pinned ${BPF_MOUNT}/{PINNED_PATH} \-j ACCEPT
 .TP
 \fB\-\-bytecode\fP \fIcode\fP
-Pass the BPF byte code format (described in the example below).
+Pass the BPF byte code format as generated by the \fBnfbpf_compile\fP utility.
 .PP
 The code format is similar to the output of the tcpdump -ddd command: one line
 that stores the number of instructions, followed by one line for each