Allow the KVP daemon to log the KVP updates triggered in the VM
with a new debug flag(-d).
When the daemon is started with this flag, it logs updates and debug
information in syslog with loglevel LOG_DEBUG. This information comes
in handy for debugging issues where the key-value pairs for certain
pools show mismatch/incorrect values.
The distro-vendors can further consume these changes and modify the
respective service files to redirect the logs to specific files as
needed.

Signed-off-by: Shradha Gupta <shradhagu...@linux.microsoft.com>
---
 Changes in v2:
 * log the debug logs in syslog(debug) instead of a seperate file that
   we will have to maintain.
 * fix the commit message to indicate the same.
---
 tools/hv/hv_kvp_daemon.c | 80 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 72 insertions(+), 8 deletions(-)

diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
index 04ba035d67e9..2ff34c2f6a8d 100644
--- a/tools/hv/hv_kvp_daemon.c
+++ b/tools/hv/hv_kvp_daemon.c
@@ -41,6 +41,7 @@
 #include <net/if.h>
 #include <limits.h>
 #include <getopt.h>
+#include <time.h>
 
 /*
  * KVP protocol: The user mode component first registers with the
@@ -83,6 +84,7 @@ enum {
 };
 
 static int in_hand_shake;
+static int debug_enabled;
 
 static char *os_name = "";
 static char *os_major = "";
@@ -153,6 +155,16 @@ static void kvp_release_lock(int pool)
        }
 }
 
+static void convert_tm_to_string(char *tm_str, size_t tm_str_size)
+{
+       struct tm tm;
+       time_t t;
+
+       time(&t);
+       gmtime_r(&t, &tm);
+       strftime(tm_str, tm_str_size, "%Y-%m-%dT%H:%M:%S", &tm);
+}
+
 static void kvp_update_file(int pool)
 {
        FILE *filep;
@@ -183,6 +195,23 @@ static void kvp_update_file(int pool)
        kvp_release_lock(pool);
 }
 
+static void kvp_dump_initial_pools(int pool)
+{
+       char tm_str[50];
+       int i;
+
+       convert_tm_to_string(tm_str, sizeof(tm_str));
+
+       syslog(LOG_DEBUG, "===Start dumping the contents of pool %d ===\n",
+              pool);
+
+       for (i = 0; i < kvp_file_info[pool].num_records; i++)
+               syslog(LOG_DEBUG, "[%s]: pool: %d, %d/%d key=%s val=%s\n",
+                      tm_str, pool, i, kvp_file_info[pool].num_records,
+                      kvp_file_info[pool].records[i].key,
+                      kvp_file_info[pool].records[i].value);
+}
+
 static void kvp_update_mem_state(int pool)
 {
        FILE *filep;
@@ -270,6 +299,8 @@ static int kvp_file_init(void)
                        return 1;
                kvp_file_info[i].num_records = 0;
                kvp_update_mem_state(i);
+               if (debug_enabled)
+                       kvp_dump_initial_pools(i);
        }
 
        return 0;
@@ -321,14 +352,28 @@ static int kvp_key_delete(int pool, const __u8 *key, int 
key_size)
 static int kvp_key_add_or_modify(int pool, const __u8 *key, int key_size,
                                 const __u8 *value, int value_size)
 {
-       int i;
-       int num_records;
        struct kvp_record *record;
+       int num_records;
+       char tm_str[50];
        int num_blocks;
+       int i;
+
+       if (debug_enabled) {
+               convert_tm_to_string(tm_str, sizeof(tm_str));
+               syslog(LOG_DEBUG, "[%s]:%s: got a KVP: pool=%d key=%s val=%s",
+                      tm_str, __func__, pool, key, value);
+       }
 
        if ((key_size > HV_KVP_EXCHANGE_MAX_KEY_SIZE) ||
-               (value_size > HV_KVP_EXCHANGE_MAX_VALUE_SIZE))
+               (value_size > HV_KVP_EXCHANGE_MAX_VALUE_SIZE)) {
+               syslog(LOG_ERR, "Got a too long key or value: key=%s, val=%s",
+                      key, value);
+
+               if (debug_enabled)
+                       syslog(LOG_DEBUG, "[%s]:[%s]: Got a too long key or 
value: pool=%d, key=%s, val=%s",
+                              tm_str, __func__, pool, key, value);
                return 1;
+       }
 
        /*
         * First update the in-memory state.
@@ -348,6 +393,9 @@ static int kvp_key_add_or_modify(int pool, const __u8 *key, 
int key_size,
                 */
                memcpy(record[i].value, value, value_size);
                kvp_update_file(pool);
+               if (debug_enabled)
+                       syslog(LOG_DEBUG, "[%s]:%s: updated: pool=%d key=%s 
val=%s",
+                              tm_str, __func__, pool, key, value);
                return 0;
        }
 
@@ -359,8 +407,10 @@ static int kvp_key_add_or_modify(int pool, const __u8 
*key, int key_size,
                record = realloc(record, sizeof(struct kvp_record) *
                         ENTRIES_PER_BLOCK * (num_blocks + 1));
 
-               if (record == NULL)
+               if (!record) {
+                       syslog(LOG_ERR, "%s: Memory alloc failure", __func__);
                        return 1;
+               }
                kvp_file_info[pool].num_blocks++;
 
        }
@@ -368,6 +418,11 @@ static int kvp_key_add_or_modify(int pool, const __u8 
*key, int key_size,
        memcpy(record[i].key, key, key_size);
        kvp_file_info[pool].records = record;
        kvp_file_info[pool].num_records++;
+
+       if (debug_enabled)
+               syslog(LOG_DEBUG, "[%s]:%s: added: pool=%d key=%s val=%s",
+                      tm_str, __func__, pool, key, value);
+
        kvp_update_file(pool);
        return 0;
 }
@@ -1662,6 +1717,7 @@ void print_usage(char *argv[])
        fprintf(stderr, "Usage: %s [options]\n"
                "Options are:\n"
                "  -n, --no-daemon        stay in foreground, don't daemonize\n"
+               "  -d, --debug-enabled    Enable debug logs(syslog debug by 
default)\n"
                "  -h, --help             print this help\n", argv[0]);
 }
 
@@ -1681,12 +1737,13 @@ int main(int argc, char *argv[])
        int daemonize = 1, long_index = 0, opt;
 
        static struct option long_options[] = {
-               {"help",        no_argument,       0,  'h' },
-               {"no-daemon",   no_argument,       0,  'n' },
-               {0,             0,                 0,  0   }
+               {"help",                no_argument,       0,  'h' },
+               {"no-daemon",           no_argument,       0,  'n' },
+               {"debug-enabled",       no_argument,       0,  'd' },
+               {0,                     0,                 0,  0   }
        };
 
-       while ((opt = getopt_long(argc, argv, "hn", long_options,
+       while ((opt = getopt_long(argc, argv, "hnd", long_options,
                                  &long_index)) != -1) {
                switch (opt) {
                case 'n':
@@ -1695,6 +1752,9 @@ int main(int argc, char *argv[])
                case 'h':
                        print_usage(argv);
                        exit(0);
+               case 'd':
+                       debug_enabled = 1;
+                       break;
                default:
                        print_usage(argv);
                        exit(EXIT_FAILURE);
@@ -1717,6 +1777,9 @@ int main(int argc, char *argv[])
         */
        kvp_get_domain_name(full_domain_name, sizeof(full_domain_name));
 
+       if (debug_enabled)
+               syslog(LOG_INFO, "Logging debug info in syslog(debug)");
+
        if (kvp_file_init()) {
                syslog(LOG_ERR, "Failed to initialize the pools");
                exit(EXIT_FAILURE);
-- 
2.34.1


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