test-nss-hosts: make buffer size configurable too and document it

docs/ENVIRONMENT.md

@@ -198,11 +198,6 @@ All tools:
   prefixed with `:` in which case the kernel command line option takes
   precedence, if it is specified as well.
 
-installed systemd tests:
-
-* `$SYSTEMD_TEST_DATA` — override the location of test data. This is useful if
-  a test executable is moved to an arbitrary location.
-
 `nss-systemd`:
 
 * `$SYSTEMD_NSS_BYPASS_SYNTHETIC=1` — if set, `nss-systemd` won't synthesize
@@ -302,6 +297,14 @@ installed systemd tests:
 * `$SYSTEMD_SYSVRCND_PATH` — Controls where `systemd-sysv-generator` looks for
   SysV init script runlevel link farms.
 
+systemd tests:
+
+* `$SYSTEMD_TEST_DATA` — override the location of test data. This is useful if
+  a test executable is moved to an arbitrary location.
+
+* `$SYSTEMD_TEST_NSS_BUFSIZE` — size of scratch buffers for "reentrant"
+  functions exported by the nss modules.
+
 fuzzers:
 
 * `$SYSTEMD_FUZZ_OUTPUT` — A boolean that specifies whether to write output to

src/test/test-nss-hosts.c

@@ -17,12 +17,15 @@
 #include "main-func.h"
 #include "nss-test-util.h"
 #include "nss-util.h"
+#include "parse-util.h"
 #include "path-util.h"
 #include "stdio-util.h"
 #include "string-util.h"
 #include "strv.h"
 #include "tests.h"
 
+static size_t arg_bufsize = 1024;
+
 static const char* af_to_string(int family, char *buf, size_t buf_len) {
         const char *name;
 
@@ -99,7 +102,7 @@ static void print_struct_hostent(struct hostent *host, const char *canon) {
 static void test_gethostbyname4_r(void *handle, const char *module, const char *name) {
         const char *fname;
         _nss_gethostbyname4_r_t f;
-        char buffer[2000];
+        char buffer[arg_bufsize];
         struct gaih_addrtuple *pat = NULL;
         int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
         int32_t ttl = INT32_MAX; /* nss-dns wants to return the lowest ttl,
@@ -151,7 +154,7 @@ static void test_gethostbyname4_r(void *handle, const char *module, const char *
 static void test_gethostbyname3_r(void *handle, const char *module, const char *name, int af) {
         const char *fname;
         _nss_gethostbyname3_r_t f;
-        char buffer[2000];
+        char buffer[arg_bufsize];
         int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
         int32_t ttl = INT32_MAX; /* nss-dns wants to return the lowest ttl,
                                     and will access this variable through *ttlp,
@@ -186,7 +189,7 @@ static void test_gethostbyname3_r(void *handle, const char *module, const char *
 static void test_gethostbyname2_r(void *handle, const char *module, const char *name, int af) {
         const char *fname;
         _nss_gethostbyname2_r_t f;
-        char buffer[2000];
+        char buffer[arg_bufsize];
         int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
         enum nss_status status;
         char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
@@ -214,7 +217,7 @@ static void test_gethostbyname2_r(void *handle, const char *module, const char *
 static void test_gethostbyname_r(void *handle, const char *module, const char *name) {
         const char *fname;
         _nss_gethostbyname_r_t f;
-        char buffer[2000];
+        char buffer[arg_bufsize];
         int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
         enum nss_status status;
         char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
@@ -245,7 +248,7 @@ static void test_gethostbyaddr2_r(void *handle,
 
         const char *fname;
         _nss_gethostbyaddr2_r_t f;
-        char buffer[2000];
+        char buffer[arg_bufsize];
         int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
         enum nss_status status;
         char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
@@ -283,7 +286,7 @@ static void test_gethostbyaddr_r(void *handle,
 
         const char *fname;
         _nss_gethostbyaddr_r_t f;
-        char buffer[2000];
+        char buffer[arg_bufsize];
         int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
         enum nss_status status;
         char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
@@ -404,8 +407,16 @@ static int parse_argv(int argc, char **argv,
         _cleanup_strv_free_ char **modules = NULL, **names = NULL;
         _cleanup_free_ struct local_address *addrs = NULL;
         size_t n_allocated = 0;
+        const char *p;
         int r, n = 0;
 
+        p = getenv("SYSTEMD_TEST_NSS_BUFSIZE");
+        if (p) {
+                r = safe_atozu(p, &arg_bufsize);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to parse $SYSTEMD_TEST_NSS_BUFSIZE");
+        }
+
         if (argc > 1)
                 modules = strv_new(argv[1]);
         else