bpf: fix convert API when libpcap missing

rte_bpf_convert() implementation depends on libpcap.
Right now it is defined only when this library is installed and
RTE_PORT_PCAP is defined.
Fix that by providing for such case stub rte_bpf_convert()
implementation that will always return an error.
To draw user attention, if proper implementation is disabled,
warning will be thrown at meson configure stage.
Also move stub for another function (rte_bpf_elf_load) into
the same place (bpf_stub.c).

Fixes: 2eccf6afbea9 ("bpf: add function to convert classic BPF to DPDK BPF")

Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

app/dumpcap/main.c

@@ -285,7 +285,8 @@ static void compile_filter(void)
 	bpf_prm = rte_bpf_convert(&bf);
 	if (bpf_prm == NULL)
 		rte_exit(EXIT_FAILURE,
-			 "bpf convert failed\n");
+			 "bpf convert failed: %s(%d)\n",
+			 rte_strerror(rte_errno), rte_errno);
 
 	if (dump_bpf) {
 		printf("cBPF program (%u insns)\n", bf.bf_len);

lib/bpf/bpf_load.c

@@ -130,21 +130,3 @@ rte_bpf_load(const struct rte_bpf_prm *prm)
 
 	return bpf;
 }
-
-#ifndef RTE_LIBRTE_BPF_ELF
-struct rte_bpf *
-rte_bpf_elf_load(const struct rte_bpf_prm *prm, const char *fname,
-	const char *sname)
-{
-	if (prm == NULL || fname == NULL || sname == NULL) {
-		rte_errno = EINVAL;
-		return NULL;
-	}
-
-	RTE_BPF_LOG(ERR, "%s() is not supported with current config\n"
-		"rebuild with libelf installed\n",
-		__func__);
-	rte_errno = ENOTSUP;
-	return NULL;
-}
-#endif

lib/bpf/bpf_stub.c

@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2018-2021 Intel Corporation
+ */
+
+#include "bpf_impl.h"
+#include <rte_errno.h>
+
+/**
+ * Contains stubs for unimplemented public API functions
+ */
+
+#ifndef RTE_LIBRTE_BPF_ELF
+struct rte_bpf *
+rte_bpf_elf_load(const struct rte_bpf_prm *prm, const char *fname,
+	const char *sname)
+{
+	if (prm == NULL || fname == NULL || sname == NULL) {
+		rte_errno = EINVAL;
+		return NULL;
+	}
+
+	RTE_BPF_LOG(ERR, "%s() is not supported with current config\n"
+		"rebuild with libelf installed\n",
+		__func__);
+	rte_errno = ENOTSUP;
+	return NULL;
+}
+#endif
+
+#ifndef RTE_PORT_PCAP
+struct rte_bpf_prm *
+rte_bpf_convert(const struct bpf_program *prog)
+{
+	if (prog == NULL) {
+		rte_errno = EINVAL;
+		return NULL;
+	}
+
+	RTE_BPF_LOG(ERR, "%s() is not supported with current config\n"
+		"rebuild with libpcap installed\n",
+		__func__);
+	rte_errno = ENOTSUP;
+	return NULL;
+}
+#endif

lib/bpf/meson.build

@@ -12,6 +12,7 @@ sources = files('bpf.c',
         'bpf_exec.c',
         'bpf_load.c',
         'bpf_pkt.c',
+        'bpf_stub.c',
         'bpf_validate.c')
 
 if arch_subdir == 'x86' and dpdk_conf.get('RTE_ARCH_64')
@@ -31,9 +32,13 @@ if dep.found()
     dpdk_conf.set('RTE_LIBRTE_BPF_ELF', 1)
     sources += files('bpf_load_elf.c')
     ext_deps += dep
+else
+     warning('libelf is missing, rte_bpf_elf_load API will be disabled')
 endif
 
 if dpdk_conf.has('RTE_PORT_PCAP')
     sources += files('bpf_convert.c')
     ext_deps += pcap_dep
+else
+     warning('RTE_PORT_PCAP is missing, rte_bpf_convert API will be disabled')
 endif

lib/bpf/rte_bpf.h

@@ -212,8 +212,6 @@ __rte_experimental
 void
 rte_bpf_dump(FILE *f, const struct ebpf_insn *buf, uint32_t len);
 
-#ifdef RTE_PORT_PCAP
-
 struct bpf_program;
 
 /**
@@ -228,13 +226,12 @@ struct bpf_program;
  *   Possible rte_errno errors include:
  *   - EINVAL - invalid parameter passed to function
  *   - ENOMEM - can't reserve enough memory
+ *   - ENOTSUP - operation not supported
  */
 __rte_experimental
 struct rte_bpf_prm *
 rte_bpf_convert(const struct bpf_program *prog);
 
-#endif
-
 #ifdef __cplusplus
 }
 #endif