utils: Introduce and use nftnl_set_str_attr()

The function consolidates the necessary code when assigning to string
pointer attributes, namely:

* Conditional free of the previous value
* Allocation of new value
* Checking for memory allocation errors
* Setting respective flag bit

A new feature previously missing in all call sites is respecting
data_len in case the buffer up to that point did not contain a NUL-char.

Signed-off-by: Phil Sutter <phil@nwl.cc>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/utils.c b/src/utils.c
index ffbad89..2f1ffd6 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -136,3 +136,17 @@ void __noreturn __abi_breakage(const char *file, int line, const char *reason)
 		       "%s:%d reason: %s\n", file, line, reason);
        exit(EXIT_FAILURE);
 }
+
+int nftnl_set_str_attr(const char **dptr, uint32_t *flags,
+		       uint16_t attr, const void *data, uint32_t data_len)
+{
+	if (*flags & (1 << attr))
+		xfree(*dptr);
+
+	*dptr = strndup(data, data_len);
+	if (!*dptr)
+		return -1;
+
+	*flags |= (1 << attr);
+	return 0;
+}