core: add support for naming file descriptors passed using socket activation

This adds support for naming file descriptors passed using socket
activation. The names are passed in a new $LISTEN_FDNAMES= environment
variable, that matches the existign $LISTEN_FDS= one and contains a
colon-separated list of names.

This also adds support for naming fds submitted to the per-service fd
store using FDNAME= in the sd_notify() message.

This also adds a new FileDescriptorName= setting for socket unit files
to set the name for fds created by socket units.

This also adds a new call sd_listen_fds_with_names(), that is similar to
sd_listen_fds(), but also returns the names of the fds.

systemd-activate gained the new --fdname= switch to specify a name for
testing socket activation.

This is based on #1247 by Maciej Wereski.

Fixes #1247.

4 files changed, 73 insertions, 3 deletions

diff --git a/src/basic/strv.c b/src/basic/strv.c
index 9524e80a6f..90f0b8c741 100644
--- a/src/basic/strv.c
+++ b/src/basic/strv.c
@@ -277,8 +277,8 @@ char **strv_split_newlines(const char *s) {
 }
 
 int strv_split_extract(char ***t, const char *s, const char *separators, ExtractFlags flags) {
-        size_t n = 0, allocated = 0;
         _cleanup_strv_free_ char **l = NULL;
+        size_t n = 0, allocated = 0;
         int r;
 
         assert(t);
@@ -302,13 +302,16 @@ int strv_split_extract(char ***t, const char *s, const char *separators, Extract
                 l[n] = NULL;
         }
 
-        if (!l)
+        if (!l) {
                 l = new0(char*, 1);
+                if (!l)
+                        return -ENOMEM;
+        }
 
         *t = l;
         l = NULL;
 
-        return 0;
+        return (int) n;
 }
 
 char *strv_join(char **l, const char *separator) {
@@ -745,3 +748,41 @@ char **strv_skip(char **l, size_t n) {
 
         return l;
 }
+
+int strv_extend_n(char ***l, const char *value, size_t n) {
+        size_t i, j, k;
+        char **nl;
+
+        assert(l);
+
+        if (!value)
+                return 0;
+        if (n == 0)
+                return 0;
+
+        /* Adds the value value n times to l */
+
+        k = strv_length(*l);
+
+        nl = realloc(*l, sizeof(char*) * (k + n + 1));
+        if (!nl)
+                return -ENOMEM;
+
+        *l = nl;
+
+        for (i = k; i < k + n; i++) {
+                nl[i] = strdup(value);
+                if (!nl[i])
+                        goto rollback;
+        }
+
+        nl[i] = NULL;
+        return 0;
+
+rollback:
+        for (j = k; j < i; i++)
+                free(nl[j]);
+
+        nl[k] = NULL;
+        return NULL;
+}
diff --git a/src/basic/strv.h b/src/basic/strv.h
index 4c4b6526de..7c1f80230a 100644
--- a/src/basic/strv.h
+++ b/src/basic/strv.h
@@ -158,3 +158,5 @@ static inline bool strv_fnmatch_or_empty(char* const* patterns, const char *s, i
 char ***strv_free_free(char ***l);
 
 char **strv_skip(char **l, size_t n);
+
+int strv_extend_n(char ***l, const char *value, size_t n);
diff --git a/src/basic/util.c b/src/basic/util.c
index c63ec0ceb0..054d45092e 100644
--- a/src/basic/util.c
+++ b/src/basic/util.c
@@ -6842,3 +6842,28 @@ int version(void) {
              SYSTEMD_FEATURES);
         return 0;
 }
+
+bool fdname_is_valid(const char *s) {
+        const char *p;
+
+        /* Validates a name for $LISTEN_NAMES. We basically allow
+         * everything ASCII that's not a control character. Also, as
+         * special exception the ":" character is not allowed, as we
+         * use that as field separator in $LISTEN_NAMES.
+         *
+         * Note that the empty string is explicitly allowed here.*/
+
+        if (!s)
+                return false;
+
+        for (p = s; *p; p++) {
+                if (*p < ' ')
+                        return false;
+                if (*p >= 127)
+                        return false;
+                if (*p == ':')
+                        return false;
+        }
+
+        return p - s < 256;
+}
diff --git a/src/basic/util.h b/src/basic/util.h
index a4e3672130..034410b8a8 100644
--- a/src/basic/util.h
+++ b/src/basic/util.h
@@ -941,3 +941,5 @@ int receive_one_fd(int transport_fd, int flags);
 void nop_signal_handler(int sig);
 
 int version(void);
+
+bool fdname_is_valid(const char *s);