Add the strlcat function to DPDK to exist alongside the strlcpy one.
While strncat is generally safe for use for concatenation, the API for the
strlcat function is perhaps a little nicer to use, and supports truncation
detection.

See commit 5364de644a4b ("eal: support strlcpy function") for more
details on the function selection logic, since we only should be using the
DPDK-provided version when no system-provided version is present.

Signed-off-by: Bruce Richardson <bruce.richard...@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yi...@intel.com>

---
V3: fix compiler error by making the test function static
CC: Reshma Pattan <reshma.pat...@intel.com>

V2: place ternary operator with regular if statement for readability
CC: Ferruh Yigit <ferruh.yi...@intel.com>
---
 .../common/include/rte_string_fns.h           | 16 +++++++
 test/test/test_string_fns.c                   | 45 +++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/lib/librte_eal/common/include/rte_string_fns.h 
b/lib/librte_eal/common/include/rte_string_fns.h
index 9a2a1ff90..35c6b003c 100644
--- a/lib/librte_eal/common/include/rte_string_fns.h
+++ b/lib/librte_eal/common/include/rte_string_fns.h
@@ -59,10 +59,25 @@ rte_strlcpy(char *dst, const char *src, size_t size)
        return (size_t)snprintf(dst, size, "%s", src);
 }
 
+/**
+ * @internal
+ * DPDK-specific version of strlcat for systems without
+ * libc or libbsd copies of the function
+ */
+static inline size_t
+rte_strlcat(char *dst, const char *src, size_t size)
+{
+       size_t l = strnlen(dst, size);
+       if (l < size)
+               return l + rte_strlcpy(&dst[l], src, size - l);
+       return l + strlen(src);
+}
+
 /* pull in a strlcpy function */
 #ifdef RTE_EXEC_ENV_BSDAPP
 #ifndef __BSD_VISIBLE /* non-standard functions are hidden */
 #define strlcpy(dst, src, size) rte_strlcpy(dst, src, size)
+#define strlcat(dst, src, size) rte_strlcat(dst, src, size)
 #endif
 
 #else /* non-BSD platforms */
@@ -71,6 +86,7 @@ rte_strlcpy(char *dst, const char *src, size_t size)
 
 #else /* no BSD header files, create own */
 #define strlcpy(dst, src, size) rte_strlcpy(dst, src, size)
+#define strlcat(dst, src, size) rte_strlcat(dst, src, size)
 
 #endif /* RTE_USE_LIBBSD */
 #endif /* BSDAPP */
diff --git a/test/test/test_string_fns.c b/test/test/test_string_fns.c
index 3f091ab92..5e105d2bb 100644
--- a/test/test/test_string_fns.c
+++ b/test/test/test_string_fns.c
@@ -129,11 +129,56 @@ test_rte_strsplit(void)
        return 0;
 }
 
+static int
+test_rte_strlcat(void)
+{
+       /* only run actual unit tests if we have system-provided strlcat */
+#if defined(__BSD_VISIBLE) || defined(RTE_USE_LIBBSD)
+#define BUF_LEN 32
+       const char dst[BUF_LEN] = "Test string";
+       const char src[] = " appended";
+       char bsd_dst[BUF_LEN];
+       char rte_dst[BUF_LEN];
+       size_t i, bsd_ret, rte_ret;
+
+       LOG("dst = '%s', strlen(dst) = %zu\n", dst, strlen(dst));
+       LOG("src = '%s', strlen(src) = %zu\n", src, strlen(src));
+       LOG("---\n");
+
+       for (i = 0; i < BUF_LEN; i++) {
+               /* initialize destination buffers */
+               memcpy(bsd_dst, dst, BUF_LEN);
+               memcpy(rte_dst, dst, BUF_LEN);
+               /* compare implementations */
+               bsd_ret = strlcat(bsd_dst, src, i);
+               rte_ret = rte_strlcat(rte_dst, src, i);
+               if (bsd_ret != rte_ret) {
+                       LOG("Incorrect retval for buf length = %zu\n", i);
+                       LOG("BSD: '%zu', rte: '%zu'\n", bsd_ret, rte_ret);
+                       return -1;
+               }
+               if (memcmp(bsd_dst, rte_dst, BUF_LEN) != 0) {
+                       LOG("Resulting buffers don't match\n");
+                       LOG("BSD: '%s', rte: '%s'\n", bsd_dst, rte_dst);
+                       return -1;
+               }
+               LOG("buffer size = %zu: dst = '%s', ret = %zu\n",
+                       i, rte_dst, rte_ret);
+       }
+       LOG("Checked %zu combinations\n", i);
+#undef BUF_LEN
+#endif /* defined(__BSD_VISIBLE) || defined(RTE_USE_LIBBSD) */
+
+       return 0;
+}
+
 static int
 test_string_fns(void)
 {
        if (test_rte_strsplit() < 0)
                return -1;
+       if (test_rte_strlcat() < 0)
+               return -1;
        return 0;
 }
 
-- 
2.20.1

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