From 58423902ce43e4ecb531c57ba9db73448ab840fe Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 19 Oct 2018 12:14:22 +0200
Subject: [PATCH] dhcp6: prefer offsetof() over sizeof() for structs with
 undefined sizes

This doesn't change anything in the generated source, but I think makes
semantically more sense, as these structures have undefined size, and we
only want to know the size up to the data field in these cases.

(cherry picked from commit 20b55f853847378b85561a4e299604d27b5cd25b)
---
 .../src/libsystemd-network/dhcp6-option.c     | 30 +++++++++----------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/systemd/src/libsystemd-network/dhcp6-option.c b/src/systemd/src/libsystemd-network/dhcp6-option.c
index 9027c14e1e..c53529d8bf 100644
--- a/src/systemd/src/libsystemd-network/dhcp6-option.c
+++ b/src/systemd/src/libsystemd-network/dhcp6-option.c
@@ -51,14 +51,14 @@ static int option_append_hdr(uint8_t **buf, size_t *buflen, uint16_t optcode,
         assert_return(*buf, -EINVAL);
         assert_return(buflen, -EINVAL);
 
-        if (optlen > 0xffff || *buflen < optlen + sizeof(DHCP6Option))
+        if (optlen > 0xffff || *buflen < optlen + offsetof(DHCP6Option, data))
                 return -ENOBUFS;
 
         option->code = htobe16(optcode);
         option->len = htobe16(optlen);
 
-        *buf += sizeof(DHCP6Option);
-        *buflen -= sizeof(DHCP6Option);
+        *buf += offsetof(DHCP6Option, data);
+        *buflen -= offsetof(DHCP6Option, data);
 
         return 0;
 }
@@ -114,8 +114,8 @@ int dhcp6_option_append_ia(uint8_t **buf, size_t *buflen, const DHCP6IA *ia) {
         ia_hdr = *buf;
         ia_buflen = *buflen;
 
-        *buf += sizeof(DHCP6Option);
-        *buflen -= sizeof(DHCP6Option);
+        *buf += offsetof(DHCP6Option, data);
+        *buflen -= offsetof(DHCP6Option, data);
 
         memcpy(*buf, (char*) ia + iaid_offset, len);
 
@@ -133,7 +133,7 @@ int dhcp6_option_append_ia(uint8_t **buf, size_t *buflen, const DHCP6IA *ia) {
                 *buf += sizeof(addr->iaaddr);
                 *buflen -= sizeof(addr->iaaddr);
 
-                ia_addrlen += sizeof(DHCP6Option) + sizeof(addr->iaaddr);
+                ia_addrlen += offsetof(DHCP6Option, data) + sizeof(addr->iaaddr);
         }
 
         r = option_append_hdr(&ia_hdr, &ia_buflen, ia->type, len + ia_addrlen);
@@ -215,7 +215,7 @@ static int option_parse_hdr(uint8_t **buf, size_t *buflen, uint16_t *optcode, si
         assert_return(optcode, -EINVAL);
         assert_return(optlen, -EINVAL);
 
-        if (*buflen < sizeof(DHCP6Option))
+        if (*buflen < offsetof(DHCP6Option, data))
                 return -ENOMSG;
 
         len = be16toh(option->len);
@@ -256,7 +256,7 @@ int dhcp6_option_parse_status(DHCP6Option *option, size_t len) {
         DHCP6StatusOption *statusopt = (DHCP6StatusOption *)option;
 
         if (len < sizeof(DHCP6StatusOption) ||
-            be16toh(option->len) + sizeof(DHCP6Option) < sizeof(DHCP6StatusOption))
+            be16toh(option->len) + offsetof(DHCP6Option, data) < sizeof(DHCP6StatusOption))
                 return -ENOBUFS;
 
         return be16toh(statusopt->status);
@@ -269,7 +269,7 @@ static int dhcp6_option_parse_address(DHCP6Option *option, DHCP6IA *ia,
         uint32_t lt_valid, lt_pref;
         int r;
 
-        if (be16toh(option->len) + sizeof(DHCP6Option) < sizeof(*addr_option))
+        if (be16toh(option->len) + offsetof(DHCP6Option, data) < sizeof(*addr_option))
                 return -ENOBUFS;
 
         lt_valid = be32toh(addr_option->iaaddr.lifetime_valid);
@@ -282,8 +282,8 @@ static int dhcp6_option_parse_address(DHCP6Option *option, DHCP6IA *ia,
                 return 0;
         }
 
-        if (be16toh(option->len) + sizeof(DHCP6Option) > sizeof(*addr_option)) {
-                r = dhcp6_option_parse_status((DHCP6Option *)addr_option->options, be16toh(option->len) + sizeof(DHCP6Option) - sizeof(*addr_option));
+        if (be16toh(option->len) + offsetof(DHCP6Option, data) > sizeof(*addr_option)) {
+                r = dhcp6_option_parse_status((DHCP6Option *)addr_option->options, be16toh(option->len) + offsetof(DHCP6Option, data) - sizeof(*addr_option));
                 if (r != 0)
                         return r < 0 ? r: 0;
         }
@@ -309,7 +309,7 @@ static int dhcp6_option_parse_pdprefix(DHCP6Option *option, DHCP6IA *ia,
         uint32_t lt_valid, lt_pref;
         int r;
 
-        if (be16toh(option->len) + sizeof(DHCP6Option) < sizeof(*pdprefix_option))
+        if (be16toh(option->len) + offsetof(DHCP6Option, data) < sizeof(*pdprefix_option))
                 return -ENOBUFS;
 
         lt_valid = be32toh(pdprefix_option->iapdprefix.lifetime_valid);
@@ -322,8 +322,8 @@ static int dhcp6_option_parse_pdprefix(DHCP6Option *option, DHCP6IA *ia,
                 return 0;
         }
 
-        if (be16toh(option->len) + sizeof(DHCP6Option) > sizeof(*pdprefix_option)) {
-                r = dhcp6_option_parse_status((DHCP6Option *)pdprefix_option->options, be16toh(option->len) + sizeof(DHCP6Option) - sizeof(*pdprefix_option));
+        if (be16toh(option->len) + offsetof(DHCP6Option, data) > sizeof(*pdprefix_option)) {
+                r = dhcp6_option_parse_status((DHCP6Option *)pdprefix_option->options, be16toh(option->len) + offsetof(DHCP6Option, data) - sizeof(*pdprefix_option));
                 if (r != 0)
                         return r < 0 ? r: 0;
         }
@@ -455,7 +455,7 @@ int dhcp6_option_parse_ia(DHCP6Option *iaoption, DHCP6IA *ia) {
 
                 case SD_DHCP6_OPTION_STATUS_CODE:
 
-                        status = dhcp6_option_parse_status(option, optlen + sizeof(DHCP6Option));
+                        status = dhcp6_option_parse_status(option, optlen + offsetof(DHCP6Option, data));
                         if (status < 0)
                                 return status;
                         if (status > 0) {