Read configuration files from /etc and /usr

Add support for the so called "stateless" configuration pattern (read
from /etc, fall back to /usr), giving system administrators a way to
define local configuration without changing any distro-provided files.

In practice this means that each configuration file FOO is loaded
from /usr/lib/iproute2/FOO unless /etc/iproute2/FOO exists.

Signed-off-by: Gioele Barabucci <gioele@svario.it>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

Makefile

@@ -16,7 +16,8 @@ endif
 
 PREFIX?=/usr
 SBINDIR?=/sbin
-CONFDIR?=/etc/iproute2
+CONF_ETC_DIR?=/etc/iproute2
+CONF_USR_DIR?=$(PREFIX)/lib/iproute2
 NETNS_RUN_DIR?=/var/run/netns
 NETNS_ETC_DIR?=/etc/netns
 DATADIR?=$(PREFIX)/share
@@ -37,7 +38,8 @@ ifneq ($(SHARED_LIBS),y)
 DEFINES+= -DNO_SHARED_LIBS
 endif
 
-DEFINES+=-DCONFDIR=\"$(CONFDIR)\" \
+DEFINES+=-DCONF_USR_DIR=\"$(CONF_USR_DIR)\" \
+         -DCONF_ETC_DIR=\"$(CONF_ETC_DIR)\" \
          -DNETNS_RUN_DIR=\"$(NETNS_RUN_DIR)\" \
          -DNETNS_ETC_DIR=\"$(NETNS_ETC_DIR)\"
 
@@ -100,11 +102,11 @@ config.mk:
 
 install: all
 	install -m 0755 -d $(DESTDIR)$(SBINDIR)
-	install -m 0755 -d $(DESTDIR)$(CONFDIR)
+	install -m 0755 -d $(DESTDIR)$(CONF_USR_DIR)
 	install -m 0755 -d $(DESTDIR)$(ARPDDIR)
 	install -m 0755 -d $(DESTDIR)$(HDRDIR)
 	@for i in $(SUBDIRS);  do $(MAKE) -C $$i install; done
-	install -m 0644 $(shell find etc/iproute2 -maxdepth 1 -type f) $(DESTDIR)$(CONFDIR)
+	install -m 0644 $(shell find etc/iproute2 -maxdepth 1 -type f) $(DESTDIR)$(CONF_USR_DIR)
 	install -m 0755 -d $(DESTDIR)$(BASH_COMPDIR)
 	install -m 0644 bash-completion/tc $(DESTDIR)$(BASH_COMPDIR)
 	install -m 0644 bash-completion/devlink $(DESTDIR)$(BASH_COMPDIR)

include/utils.h

@@ -38,8 +38,11 @@ extern int numeric;
 extern bool do_all;
 extern int echo_request;
 
-#ifndef CONFDIR
-#define CONFDIR		"/etc/iproute2"
+#ifndef CONF_USR_DIR
+#define CONF_USR_DIR "/usr/lib/iproute2"
+#endif
+#ifndef CONF_ETC_DIR
+#define CONF_ETC_DIR "/etc/iproute2"
 #endif
 
 #define SPRINT_BSIZE 64

lib/bpf_legacy.c

@@ -2751,7 +2751,7 @@ static bool bpf_pinning_reserved(uint32_t pinning)
 	}
 }
 
-static void bpf_hash_init(struct bpf_elf_ctx *ctx, const char *db_file)
+static int bpf_hash_init(struct bpf_elf_ctx *ctx, const char *db_file)
 {
 	struct bpf_hash_entry *entry;
 	char subpath[PATH_MAX] = {};
@@ -2761,14 +2761,14 @@ static void bpf_hash_init(struct bpf_elf_ctx *ctx, const char *db_file)
 
 	fp = fopen(db_file, "r");
 	if (!fp)
-		return;
+		return -errno;
 
 	while ((ret = bpf_read_pin_mapping(fp, &pinning, subpath))) {
 		if (ret == -1) {
 			fprintf(stderr, "Database %s is corrupted at: %s\n",
 				db_file, subpath);
 			fclose(fp);
-			return;
+			return -EINVAL;
 		}
 
 		if (bpf_pinning_reserved(pinning)) {
@@ -2796,6 +2796,8 @@ static void bpf_hash_init(struct bpf_elf_ctx *ctx, const char *db_file)
 	}
 
 	fclose(fp);
+
+	return 0;
 }
 
 static void bpf_hash_destroy(struct bpf_elf_ctx *ctx)
@@ -2924,7 +2926,9 @@ static int bpf_elf_ctx_init(struct bpf_elf_ctx *ctx, const char *pathname,
 	}
 
 	bpf_save_finfo(ctx);
-	bpf_hash_init(ctx, CONFDIR "/bpf_pinning");
+	bpf_hash_init(ctx, CONF_ETC_DIR "/bpf_pinning");
+	if (ret == -ENOENT)
+		ret = bpf_hash_init(ctx, CONF_USR_DIR "/bpf_pinning");
 
 	return 0;
 out_free: