[PATCH] gbproxy: Add gbprox_clear_patch_filter() (Coverity)

[Jacob Erlbeck]

Add a separate function to clear the IMSI filter to be used instead of
gbprox_set_patch_filter(cfg, NULL, ...). Albeit it fixes a Coverity
issue (Unchecked return value), it is a false positive, since the
return value is always 0 in these cases. Nevertheless it is more
obvious what happens when an explicit clear function is called. Using
NULL as filter argument of gbprox_set_patch_filter still clears the
filter.

Fixes: Coverity CID 1231255
Sponsored-by: On-Waves ehf
---
 openbsc/include/openbsc/gb_proxy.h   |  1 +
 openbsc/src/gprs/gb_proxy.c          | 13 +++++++++----
 openbsc/src/gprs/gb_proxy_vty.c      |  4 ++--
 openbsc/tests/gbproxy/gbproxy_test.c |  6 ++++++
 4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/openbsc/include/openbsc/gb_proxy.h 
b/openbsc/include/openbsc/gb_proxy.h
index 039a9a1..d6dde10 100644
--- a/openbsc/include/openbsc/gb_proxy.h
+++ b/openbsc/include/openbsc/gb_proxy.h
@@ -115,6 +115,7 @@ void gbprox_reset(struct gbproxy_config *cfg);
 
 int gbprox_set_patch_filter(struct gbproxy_config *cfg, const char *filter,
                const char **err_msg);
+void gbprox_clear_patch_filter(struct gbproxy_config *cfg);
 
 void gbprox_delete_tlli(struct gbproxy_peer *peer,
                               struct gbproxy_tlli_info *tlli_info);
diff --git a/openbsc/src/gprs/gb_proxy.c b/openbsc/src/gprs/gb_proxy.c
index a8ce3cc..64fb55b 100644
--- a/openbsc/src/gprs/gb_proxy.c
+++ b/openbsc/src/gprs/gb_proxy.c
@@ -481,16 +481,21 @@ static void gbprox_delete_tllis(struct gbproxy_peer *peer)
        OSMO_ASSERT(llist_empty(&state->enabled_tllis));
 }
 
+void gbprox_clear_patch_filter(struct gbproxy_config *cfg)
+{
+       if (cfg->check_imsi) {
+               regfree(&cfg->imsi_re_comp);
+               cfg->check_imsi = 0;
+       }
+}
+
 int gbprox_set_patch_filter(struct gbproxy_config *cfg, const char *filter,
                const char **err_msg)
 {
        static char err_buf[300];
        int rc;
 
-       if (cfg->check_imsi) {
-               regfree(&cfg->imsi_re_comp);
-               cfg->check_imsi = 0;
-       }
+       gbprox_clear_patch_filter(cfg);
 
        if (!filter)
                return 0;
diff --git a/openbsc/src/gprs/gb_proxy_vty.c b/openbsc/src/gprs/gb_proxy_vty.c
index ec73ae6..9574a45 100644
--- a/openbsc/src/gprs/gb_proxy_vty.c
+++ b/openbsc/src/gprs/gb_proxy_vty.c
@@ -193,7 +193,7 @@ static int set_core_apn(struct vty *vty, const char *apn, 
const char *filter)
                talloc_free(g_cfg->core_apn);
                g_cfg->core_apn = NULL;
                g_cfg->core_apn_size = 0;
-               gbprox_set_patch_filter(g_cfg, NULL, NULL);
+               gbprox_clear_patch_filter(g_cfg);
                return CMD_SUCCESS;
        }
 
@@ -206,7 +206,7 @@ static int set_core_apn(struct vty *vty, const char *apn, 
const char *filter)
        }
 
        if (!filter) {
-               gbprox_set_patch_filter(g_cfg, NULL, NULL);
+               gbprox_clear_patch_filter(g_cfg);
        } else if (gbprox_set_patch_filter(g_cfg, filter, &err_msg) != 0) {
                vty_out(vty, "Match expression invalid: %s%s",
                        err_msg, VTY_NEWLINE);
diff --git a/openbsc/tests/gbproxy/gbproxy_test.c 
b/openbsc/tests/gbproxy/gbproxy_test.c
index 964c6da..5363749 100644
--- a/openbsc/tests/gbproxy/gbproxy_test.c
+++ b/openbsc/tests/gbproxy/gbproxy_test.c
@@ -1571,6 +1571,12 @@ static void test_gbproxy_imsi_matching(void)
        OSMO_ASSERT(gbprox_set_patch_filter(&cfg, NULL, &err_msg) == 0);
        OSMO_ASSERT(cfg.check_imsi == 0);
 
+       OSMO_ASSERT(gbprox_set_patch_filter(&cfg, filter_re2, &err_msg) == 0);
+       OSMO_ASSERT(cfg.check_imsi == 1);
+
+       gbprox_clear_patch_filter(&cfg);
+       OSMO_ASSERT(cfg.check_imsi == 0);
+
        peer = gbproxy_peer_alloc(&cfg, 20);
 
        OSMO_ASSERT(gbprox_set_patch_filter(&cfg, filter_re2, &err_msg) == 0);
-- 
1.9.1