From 101ac54a7d39cf1470ab72e4b91c198381f7b4cd Mon Sep 17 00:00:00 2001
From: Andreas Karlsson <andreas.karlsson@rt-labs.com>
Date: Fri, 14 Aug 2020 15:04:46 +0200
Subject: [PATCH] Don't always include optional IP parameter lengths

Obvious fix, the optional IP parameters length should
only be included in total length if they are included.

fixes #421
---
 soem/ethercateoe.c | 32 +++++++++++++-------------------
 soem/ethercateoe.h |  2 ++
 2 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/soem/ethercateoe.c b/soem/ethercateoe.c
index 5a40b13..a444565 100644
--- a/soem/ethercateoe.c
+++ b/soem/ethercateoe.c
@@ -94,45 +94,43 @@ int ecx_EOEsetIp(ecx_contextt *context, uint16 slave, uint8 port, eoe_param_t *
       EOE_HDR_LAST_FRAGMENT);
    EOEp->frameinfo2 = 0;
   
-   /* The EoE frame will include "empty" IP/DNS entries, makes wireshark happy.
-    * Specification say they are optional, TwinCAT include empty entries.
-    */
    if (ipparam->mac_set)
    {
       flags |= EOE_PARAM_MAC_INCLUDE;
       memcpy(&EOEp->data[data_offset], ipparam->mac.addr, EOE_ETHADDR_LENGTH);
+      data_offset += EOE_ETHADDR_LENGTH;
    }
-   data_offset += EOE_ETHADDR_LENGTH;
    if (ipparam->ip_set)
    {
       flags |= EOE_PARAM_IP_INCLUDE;
       EOE_ip_uint32_to_byte(&ipparam->ip, &EOEp->data[data_offset]);
+      data_offset += EOE_IP4_LENGTH;
    }
-   data_offset += 4;
    if (ipparam->subnet_set)
    {
       flags |= EOE_PARAM_SUBNET_IP_INCLUDE;
       EOE_ip_uint32_to_byte(&ipparam->subnet, &EOEp->data[data_offset]);
+      data_offset += EOE_IP4_LENGTH;
    }
-   data_offset += 4;
    if (ipparam->default_gateway_set)
    {
       flags |= EOE_PARAM_DEFAULT_GATEWAY_INCLUDE;
       EOE_ip_uint32_to_byte(&ipparam->default_gateway, &EOEp->data[data_offset]);
+      data_offset += EOE_IP4_LENGTH;
    }
-   data_offset += 4;
    if (ipparam->dns_ip_set)
    {
       flags |= EOE_PARAM_DNS_IP_INCLUDE;
       EOE_ip_uint32_to_byte(&ipparam->dns_ip, &EOEp->data[data_offset]);
+      data_offset += EOE_IP4_LENGTH;
    }
-   data_offset += 4;
    if (ipparam->dns_name_set)
    {
+      /* TwinCAT include EOE_DNS_NAME_LENGTH chars even if name is shorter */
       flags |= EOE_PARAM_DNS_NAME_INCLUDE;
       memcpy(&EOEp->data[data_offset], (void *)ipparam->dns_name, EOE_DNS_NAME_LENGTH);
+      data_offset += EOE_DNS_NAME_LENGTH;
    }
-   data_offset += EOE_DNS_NAME_LENGTH;
 
    EOEp->mbxheader.length = htoes(EOE_PARAM_OFFSET + data_offset);
    EOEp->data[0] = flags;
@@ -231,10 +229,6 @@ int ecx_EOEgetIp(ecx_contextt *context, uint16 slave, uint8 port, eoe_param_t *
             }
             else
             {
-               /* The EoE frame will include "empty" IP/DNS entries,  makes 
-                * wireshark happy. Specification say they are optional, TwinCAT 
-                * include empty entries.
-                */
                flags = aEOEp->data[0];
                if (flags & EOE_PARAM_MAC_INCLUDE)
                {
@@ -242,36 +236,36 @@ int ecx_EOEgetIp(ecx_contextt *context, uint16 slave, uint8 port, eoe_param_t *
                      &aEOEp->data[data_offset], 
                      EOE_ETHADDR_LENGTH);
                   ipparam->mac_set = 1;
+                  data_offset += EOE_ETHADDR_LENGTH;
                }
-               data_offset += EOE_ETHADDR_LENGTH;
                if (flags & EOE_PARAM_IP_INCLUDE)
                {
                   EOE_ip_byte_to_uint32(&aEOEp->data[data_offset],
                      &ipparam->ip);
                   ipparam->ip_set = 1;
+                  data_offset += EOE_IP4_LENGTH;
                }
-               data_offset += 4;
                if (flags & EOE_PARAM_SUBNET_IP_INCLUDE)
                {
                   EOE_ip_byte_to_uint32(&aEOEp->data[data_offset],
                      &ipparam->subnet);
                   ipparam->subnet_set = 1;
+                  data_offset += EOE_IP4_LENGTH;
                }
-               data_offset += 4;
                if (flags & EOE_PARAM_DEFAULT_GATEWAY_INCLUDE)
                {
                   EOE_ip_byte_to_uint32(&aEOEp->data[data_offset],
                      &ipparam->default_gateway);
                   ipparam->default_gateway_set = 1;
+                  data_offset += EOE_IP4_LENGTH;
                }
-               data_offset += 4;
                if (flags & EOE_PARAM_DNS_IP_INCLUDE)
                {
                   EOE_ip_byte_to_uint32(&aEOEp->data[data_offset],
                      &ipparam->dns_ip);
                   ipparam->dns_ip_set = 1;
+                  data_offset += EOE_IP4_LENGTH;
                }
-               data_offset += 4;
                if (flags & EOE_PARAM_DNS_NAME_INCLUDE)
                {
                   uint16_t dns_len;
@@ -286,8 +280,8 @@ int ecx_EOEgetIp(ecx_contextt *context, uint16 slave, uint8 port, eoe_param_t *
                   /* Assume ZERO terminated string */
                   memcpy(ipparam->dns_name, &aEOEp->data[data_offset], dns_len);
                   ipparam->dns_name_set = 1;
+                  data_offset += EOE_DNS_NAME_LENGTH;
                }
-               data_offset += EOE_DNS_NAME_LENGTH;
                /* Something os not correct, flag the error */
                if(data_offset > eoedatasize)
                {
diff --git a/soem/ethercateoe.h b/soem/ethercateoe.h
index b517398..a4c2c73 100644
--- a/soem/ethercateoe.h
+++ b/soem/ethercateoe.h
@@ -22,6 +22,8 @@ extern "C"
 #define EOE_DNS_NAME_LENGTH  32
 /** Ethernet address length not including VLAN */
 #define EOE_ETHADDR_LENGTH    6
+/** IPv4 address length */
+#define EOE_IP4_LENGTH        sizeof(uint32_t)
 
 #define EOE_MAKEU32(a,b,c,d) (((uint32_t)((a) & 0xff) << 24) | \
                             ((uint32_t)((b) & 0xff) << 16) | \