conn->want conversion: Fix fuse_apply_conn_info_opts()

fuse_apply_conn_info_opts() was applying to 'want_ext',
which would cause conflicts with 'want' if the application
applied its own flags to 'conn->want'.

Solution is:
    - to move fuse_{set,unset,get}_feature_flag and
      convert_to_conn_want_ext() to fuse_lowlevel.c and
      to define them as part of the public API, although
      convert_to_conn_want_ext() should not be used - it is
      currently needed to be a public function due as it needs
      to be defined for the tests.

Related to https://github.com/libfuse/libfuse/issues/1171 and
https://github.com/libfuse/libfuse/pull/1172.

Closes: https://github.com/libfuse/libfuse/issues/1171
Signed-off-by: Bernd Schubert <bschubert@ddn.com>

7 files changed, 99 insertions, 47 deletions

diff --git a/lib/fuse.c b/lib/fuse.c
index ccf4aeb..b116661 100644
--- a/lib/fuse.c
+++ b/lib/fuse.c
@@ -2560,15 +2560,8 @@ void fuse_fs_init(struct fuse_fs *fs, struct fuse_conn_info *conn,
 		fuse_unset_feature_flag(conn, FUSE_CAP_POSIX_LOCKS);
 	if (!fs->op.flock)
 		fuse_unset_feature_flag(conn, FUSE_CAP_FLOCK_LOCKS);
-	if (fs->op.init) {
-		uint64_t want_ext_default = conn->want_ext;
-		uint32_t want_default = fuse_lower_32_bits(conn->want_ext);
-
-		conn->want = want_default;
+	if (fs->op.init)
 		fs->user_data = fs->op.init(conn, cfg);
-
-		convert_to_conn_want_ext(conn, want_ext_default, want_default);
-	}
 }
 
 static int fuse_init_intr_signal(int signum, int *installed);
diff --git a/lib/fuse_i.h b/lib/fuse_i.h
index 14d99ad..80ec803 100644
--- a/lib/fuse_i.h
+++ b/lib/fuse_i.h
@@ -106,6 +106,13 @@ struct fuse_session {
 
 	/* io_uring */
 	struct fuse_session_uring uring;
+
+	/*
+	 * conn->want and conn_want_ext options set by libfuse , needed
+	 * to correctly convert want to want_ext
+	 */
+	uint32_t conn_want;
+	uint64_t conn_want_ext;
 };
 
 struct fuse_chan {
@@ -250,36 +257,5 @@ int fuse_loop_cfg_verify(struct fuse_loop_config *config);
 /* room needed in buffer to accommodate header */
 #define FUSE_BUFFER_HEADER_SIZE 0x1000
 
-/**
- * Get the wanted capability flags, converting from old format if necessary
- */
-static inline int convert_to_conn_want_ext(struct fuse_conn_info *conn,
-					   uint64_t want_ext_default,
-					   uint32_t want_default)
-{
-	/*
-	 * Convert want to want_ext if necessary.
-	 * For the high level interface this function might be called
-	 * twice, once from the high level interface and once from the
-	 * low level interface. Both, with different want_ext_default and
-	 * want_default values. In order to suppress a failure for the
-	 * second call, we check if the lower 32 bits of want_ext are
-	 * already set to the value of want.
-	 */
-	if (conn->want != want_default &&
-	    fuse_lower_32_bits(conn->want_ext) != conn->want) {
-		if (conn->want_ext != want_ext_default)
-			return -EINVAL;
-
-		/* high bits from want_ext, low bits from want */
-		conn->want_ext = fuse_higher_32_bits(conn->want_ext) |
-				 conn->want;
-	}
-
-	/* ensure there won't be a second conversion */
-	conn->want = fuse_lower_32_bits(conn->want_ext);
-
-	return 0;
-}
 
 #endif /* LIB_FUSE_I_H_*/
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 9fb793b..c2f3ccb 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -2435,6 +2435,77 @@ static bool want_flags_valid(uint64_t capable, uint64_t want)
 	return true;
 }
 
+/**
+ * Get the wanted capability flags, converting from old format if necessary
+ */
+int fuse_convert_to_conn_want_ext(struct fuse_conn_info *conn)
+{
+	struct fuse_session *se = container_of(conn, struct fuse_session, conn);
+
+	/*
+	 * Convert want to want_ext if necessary.
+	 * For the high level interface this function might be called
+	 * twice, once from the high level interface and once from the
+	 * low level interface. Both, with different want_ext_default and
+	 * want_default values. In order to suppress a failure for the
+	 * second call, we check if the lower 32 bits of want_ext are
+	 * already set to the value of want.
+	 */
+	if (conn->want != se->conn_want &&
+	    fuse_lower_32_bits(conn->want_ext) != conn->want) {
+		if (conn->want_ext != se->conn_want_ext) {
+			fuse_log(FUSE_LOG_ERR,
+				"%s: Both conn->want_ext and conn->want are set.\n"
+				"want=%x, want_ext=%lx, se->want=%lx se->want_ext=%lx\n",
+				__func__, conn->want, conn->want_ext,
+				se->conn_want, se->conn_want_ext);
+			return -EINVAL;
+		}
+
+		/* high bits from want_ext, low bits from want */
+		conn->want_ext = fuse_higher_32_bits(conn->want_ext) |
+				 conn->want;
+	}
+
+	/* ensure there won't be a second conversion */
+	conn->want = fuse_lower_32_bits(conn->want_ext);
+
+	return 0;
+}
+
+bool fuse_set_feature_flag(struct fuse_conn_info *conn,
+					 uint64_t flag)
+{
+	struct fuse_session *se = container_of(conn, struct fuse_session, conn);
+
+	if (conn->capable_ext & flag) {
+		conn->want_ext |= flag;
+		se->conn_want_ext |= flag;
+		conn->want  |= flag;
+		se->conn_want |= flag;
+		return true;
+	}
+	return false;
+}
+
+void fuse_unset_feature_flag(struct fuse_conn_info *conn,
+					 uint64_t flag)
+{
+	struct fuse_session *se = container_of(conn, struct fuse_session, conn);
+
+	conn->want_ext &= ~flag;
+	se->conn_want_ext &= ~flag;
+	conn->want  &= ~flag;
+	se->conn_want &= ~flag;
+}
+
+bool fuse_get_feature_flag(struct fuse_conn_info *conn,
+					     uint64_t flag)
+{
+	return conn->capable_ext & flag ? true : false;
+}
+
+
 /* Prevent bogus data races (bogus since "init" is called before
  * multi-threading becomes relevant */
 static __attribute__((no_sanitize("thread"))) void
@@ -2603,12 +2674,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 
 	se->got_init = 1;
 	if (se->op.init) {
-		uint64_t want_ext_default = se->conn.want_ext;
-		uint32_t want_default = fuse_lower_32_bits(se->conn.want_ext);
-
 		// Apply the first 32 bits of capable_ext to capable
 		se->conn.capable = fuse_lower_32_bits(se->conn.capable_ext);
-		se->conn.want = want_default;
 
 		se->op.init(se->userdata, &se->conn);
 
@@ -2617,8 +2684,7 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 		 * se->conn.want_ext
 		 * Userspace might still use conn.want - we need to convert it
 		 */
-		convert_to_conn_want_ext(&se->conn, want_ext_default,
-					      want_default);
+		fuse_convert_to_conn_want_ext(&se->conn);
 	}
 
 	if (!want_flags_valid(se->conn.capable_ext, se->conn.want_ext)) {
diff --git a/lib/fuse_versionscript b/lib/fuse_versionscript
index 22c59e1..ab57d7c 100644
--- a/lib/fuse_versionscript
+++ b/lib/fuse_versionscript
@@ -205,6 +205,12 @@ FUSE_3.17 {
 FUSE_3.18 {
 	global:
 		fuse_req_is_uring;
+		fuse_set_feature_flag;
+		fuse_unset_feature_flag;
+		fuse_get_feature_flag;
+
+		# Not part of public API, for internal test use only
+		fuse_convert_to_conn_want_ext;
 } FUSE_3.17;
 
 # Local Variables:
diff --git a/lib/helper.c b/lib/helper.c
index 5811c53..ced70a2 100644
--- a/lib/helper.c
+++ b/lib/helper.c
@@ -430,13 +430,13 @@ void fuse_apply_conn_info_opts(struct fuse_conn_info_opts *opts,
 #define LL_ENABLE(cond, cap)                     \
 	do {                                     \
 		if (cond)                        \
-			conn->want_ext |= (cap); \
+			fuse_set_feature_flag(conn, cap); \
 	} while (0)
 
 #define LL_DISABLE(cond, cap)                     \
 	do {                                      \
 		if (cond)                         \
-			conn->want_ext &= ~(cap); \
+			fuse_unset_feature_flag(conn, cap); \
 	} while (0)
 
 	LL_ENABLE(opts->splice_read, FUSE_CAP_SPLICE_READ);
diff --git a/lib/util.c b/lib/util.c
index 00f1e1a..7583d47 100644
--- a/lib/util.c
+++ b/lib/util.c
@@ -10,7 +10,14 @@
 #include <stdlib.h>
 #include <errno.h>
 
+#ifndef FUSE_USE_VERSION
+#define FUSE_USE_VERSION (FUSE_MAKE_VERSION(3, 18))
+#endif
+
 #include "util.h"
+#include "fuse_log.h"
+#include "fuse_lowlevel.h"
+#include <stdio.h>
 
 int libfuse_strtol(const char *str, long *res)
 {
@@ -44,3 +51,4 @@ void fuse_set_thread_name(unsigned long tid, const char *name)
 	(void)name;
 #endif
 }
+
diff --git a/lib/util.h b/lib/util.h
index 96b59d3..d91a5e9 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -2,12 +2,15 @@
 #define FUSE_UTIL_H_
 
 #include <stdint.h>
+#include <stdbool.h>
 
 #define ROUND_UP(val, round_to) (((val) + (round_to - 1)) & ~(round_to - 1))
 
 #define likely(x) __builtin_expect(!!(x), 1)
 #define unlikely(x) __builtin_expect(!!(x), 0)
 
+struct fuse_conn_info;
+
 int libfuse_strtol(const char *str, long *res);
 void fuse_set_thread_name(unsigned long tid, const char *name);