snmp: update target port handling and improve peername construction

Signed-off-by: k402xxxcenxxx <[email protected]>

Author: k402xxxcenxxx

plugins/in_snmp/in_snmp.c

@@ -378,7 +378,31 @@ static int in_snmp_init(struct flb_input_instance *in,
 
     snmp_sess_init(&ctx->session);
 
-    ctx->session.peername = ctx->target_host;
+    {
+        flb_plg_error(ctx->ins, "target_port : %d", ctx->target_port);
+
+        /* compose peername by using target_host and port */
+        size_t host_len = strlen(ctx->target_host);
+        int port_len = snprintf(NULL, 0, "%d", ctx->target_port);
+        size_t static_len = strlen("udp::"); // "udp:" + ":"
+        size_t need = static_len + host_len + port_len + 1;
+        char *peer = flb_calloc(1, need);
+        if (!peer) {
+            flb_plg_error(ctx->ins, "oom building peername");
+            flb_free(ctx);
+            return -1;
+        }
+        int written = snprintf(peer, need, "udp:%s:%d", ctx->target_host, ctx->target_port);
+        if (written < 0 || (size_t)written >= need) {
+            flb_plg_error(ctx->ins, "peername truncated, need %zu bytes", need);
+            flb_free(peer);
+            flb_free(ctx);
+            return -1;
+        }
+        flb_plg_error(ctx->ins, "peer : %s", peer);
+
+        ctx->session.peername = peer;
+    }
 
     if (strcmp(ctx->version, "1") == 0) {
         ctx->session.version = SNMP_VERSION_1;
@@ -434,8 +458,8 @@ static struct flb_config_map config_map[] = {
     "set the target host IP to collect metrics through SNMP."
    },
    {
-    FLB_CONFIG_MAP_INT, "port", "161",
-    0, FLB_TRUE, offsetof(struct flb_snmp, port),
+    FLB_CONFIG_MAP_INT, "target_port", "161",
+    0, FLB_TRUE, offsetof(struct flb_snmp, target_port),
     "set the host port to collect metrics through SNMP."
    },
    {

plugins/in_snmp/in_snmp.h

@@ -14,7 +14,7 @@ struct flb_snmp {
     netsnmp_session session;
 
     char *target_host;
-    int port;
+    int target_port;
     int timeout;
     char *version;
     char *community;