If BPF_STMT or BPF_JUMP is defined, undefine them before redefining them.

Do that instead of just not defining the BPF stuff if __LINUX_FILTER_H__
is defined.  That way, our definitions override the <linux/filter.h>
definitions.  If those differ from our definitions, we want our
definitions, at least when building the BPF code generator, so that, for
example, we support the modulo and XOR operators.  (If the kernel
doesn't support them, the attempt to set the kernel filter will fail if
we use BPF_MOD or BPF_XOR, and we'll fall back on doing userland
filtering.)

This should address GitHub issue #987.

(cherry picked from commit 2abff2bc2dbd2be3888330e9ce0df298dd441d8a)

diff --git a/pcap/bpf.h b/pcap/bpf.h
index ccb93cc749730dd4df7fbe073439edafc50c365a..bfc60d2c72cf782346c409d4b4a1160341e74f5c 100644 (file)
--- a/pcap/bpf.h
+++ b/pcap/bpf.h
@@ -119,8 +119,6 @@ struct bpf_program {
 
 #include <pcap/dlt.h>
 
-#ifndef __LINUX_FILTER_H__
-
 /*
  * The instruction encodings.
  *
@@ -241,8 +239,6 @@ struct bpf_program {
 /*                             0xf0    reserved */
 /*                             0xf8    reserved */
 
-#endif /* __LINUX_FILTER_H__ */
-
 /*
  * The instruction data structure.
  */
@@ -253,16 +249,25 @@ struct bpf_insn {
        bpf_u_int32 k;
 };
 
-#ifndef __LINUX_FILTER_H__
-
 /*
  * Macros for insn array initializers.
+ *
+ * In case somebody's included <linux/filter.h>, or something else that
+ * gives the kernel's definitions of BPF statements, get rid of its
+ * definitions, so we can supply ours instead.  If some kernel's
+ * definitions aren't *binary-compatible* with what BPF has had
+ * since it first sprung from the brows of Van Jacobson and Steve
+ * McCanne, that kernel should be fixed.
  */
+#ifdef BPF_STMT
+#undef BPF_STMT
+#endif
 #define BPF_STMT(code, k) { (u_short)(code), 0, 0, k }
+#ifdef BPF_JUMP
+#undef BPF_JUMP
+#endif
 #define BPF_JUMP(code, k, jt, jf) { (u_short)(code), jt, jf, k }
 
-#endif /* __LINUX_FILTER_H__ */
-
 PCAP_AVAILABLE_0_4
 PCAP_API u_int bpf_filter(const struct bpf_insn *, const u_char *, u_int, u_int);