sd-json: add sd_json_dispatch_pid()

src/basic/process-util.h

@@ -148,10 +148,21 @@ static inline bool sched_priority_is_valid(int i) {
         return i >= 0 && i <= sched_get_priority_max(SCHED_RR);
 }
 
+#define PID_AUTOMATIC ((pid_t) INT_MIN) /* special value indicating "acquire pid from connection peer */
+#define PID_INVALID   ((pid_t) 0)       /* default value for "invalid pid" */
+
 static inline bool pid_is_valid(pid_t p) {
         return p > 0;
 }
 
+static inline bool pid_is_automatic(pid_t p) {
+        return p == PID_AUTOMATIC;
+}
+
+static inline bool pid_is_valid_or_automatic(pid_t p) {
+        return pid_is_valid(p) || pid_is_automatic(p);
+}
+
 pid_t getpid_cached(void);
 void reset_cached_pid(void);
 

src/libsystemd/libsystemd.sym

@@ -864,6 +864,7 @@ global:
         sd_json_dispatch_strv;
         sd_json_dispatch_tristate;
         sd_json_dispatch_uid_gid;
+        sd_json_dispatch_pid;
         sd_json_dispatch_uint16;
         sd_json_dispatch_uint32;
         sd_json_dispatch_uint64;

src/libsystemd/sd-json/sd-json.c

@@ -29,6 +29,7 @@
 #include "memory-util.h"
 #include "memstream-util.h"
 #include "path-util.h"
+#include "process-util.h"
 #include "set.h"
 #include "signal-util.h"
 #include "string-table.h"
@@ -5507,6 +5508,44 @@ _public_ int sd_json_dispatch_uid_gid(const char *name, sd_json_variant *variant
         return 0;
 }
 
+_public_ int sd_json_dispatch_pid(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
+        /* pid_t is a signed type, but we don't consider negative values as valid.
+         * There is a special treatment for 0 if SD_JSON_RELAX flag present. */
+
+        pid_t *pid = userdata;
+        uint32_t k;
+        int r;
+
+        assert_return(variant, -EINVAL);
+        assert_cc(sizeof(pid_t) == sizeof(uint32_t));
+
+        if (sd_json_variant_is_null(variant)) {
+                *pid = PID_INVALID;
+                return 0;
+        }
+
+        r = sd_json_dispatch_uint32(name, variant, flags, &k);
+        if (r < 0)
+                return r;
+
+        if (k == 0) {
+                if (!FLAGS_SET(flags, SD_JSON_RELAX))
+                        goto invalid_value;
+
+                *pid = PID_AUTOMATIC;
+                return 0;
+        }
+
+        if (!pid_is_valid(k))
+                goto invalid_value;
+
+        *pid = k;
+        return 0;
+
+invalid_value:
+        return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not a valid PID.", strna(name));
+}
+
 _public_ int sd_json_dispatch_id128(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
         sd_id128_t *uuid = userdata;
         int r;

src/systemd/sd-json.h

@@ -328,6 +328,7 @@ int sd_json_dispatch_int8(const char *name, sd_json_variant *variant, sd_json_di
 int sd_json_dispatch_uint8(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int sd_json_dispatch_double(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int sd_json_dispatch_uid_gid(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
+int sd_json_dispatch_pid(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int sd_json_dispatch_id128(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int sd_json_dispatch_signal(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int sd_json_dispatch_unsupported(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);