Use more specific ipmi error codes

Most errors in the handler were returning an unsupported code and not a
more specific code articulating the failure.  Update the code to use
more specific errors.

Change-Id: I7f517d094245e8e1a6169f43582522889bb895d0
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/cable.cpp b/cable.cpp
index ea362b2..69eb8c9 100644
--- a/cable.cpp
+++ b/cable.cpp
@@ -59,7 +59,7 @@
     {
         std::fprintf(stderr, "Invalid command length: %u\n",
                      static_cast<uint32_t>(*dataLen));
-        return IPMI_CC_INVALID;
+        return IPMI_CC_REQ_DATA_LEN_INVALID;
     }
 
     const auto request =
@@ -70,7 +70,7 @@
     {
         std::fprintf(stderr, "Invalid string length: %d\n",
                      request->if_name_len);
-        return IPMI_CC_INVALID;
+        return IPMI_CC_REQ_DATA_LEN_INVALID;
     }
 
     // Verify the request buffer contains the object and the string.
@@ -78,7 +78,7 @@
     {
         std::fprintf(stderr, "*dataLen too small: %u\n",
                      static_cast<uint32_t>(*dataLen));
-        return IPMI_CC_INVALID;
+        return IPMI_CC_REQ_DATA_LEN_INVALID;
     }
 
     // Maximum length one can specify, plus null terminator.
@@ -96,7 +96,7 @@
     if (name.find("/") != std::string::npos)
     {
         std::fprintf(stderr, "Invalid or illegal name: '%s'\n", nameBuf);
-        return IPMI_CC_INVALID;
+        return IPMI_CC_INVALID_FIELD_REQUEST;
     }
 
     opath << "/sys/class/net/" << name << "/statistics/rx_packets";
@@ -106,7 +106,7 @@
     if (!fs::exists(path, ec))
     {
         std::fprintf(stderr, "Path: '%s' doesn't exist.\n", path.c_str());
-        return IPMI_CC_INVALID;
+        return IPMI_CC_INVALID_FIELD_REQUEST;
     }
     // We're uninterested in the state of ec.
 
@@ -121,7 +121,7 @@
     }
     catch (std::ios_base::failure& fail)
     {
-        return IPMI_CC_INVALID;
+        return IPMI_CC_UNSPECIFIED_ERROR;
     }
 
     struct CableReply reply;