NetworkPkg/UefiPxeBcDxe: handle competing DHCP servers (more) gracefully

[mirror_edk2.git] / NetworkPkg / UefiPxeBcDxe / PxeBcBoot.c

diff --git a/NetworkPkg/UefiPxeBcDxe/PxeBcBoot.c b/NetworkPkg/UefiPxeBcDxe/PxeBcBoot.c
index 10bbb06f759345d4e2d4ffa3133664b0dd03ff15..d062a526077b270d35867d22012578e58445bd29 100644 (file)
--- a/NetworkPkg/UefiPxeBcDxe/PxeBcBoot.c
+++ b/NetworkPkg/UefiPxeBcDxe/PxeBcBoot.c
@@ -482,7 +482,20 @@ PxeBcDhcp4BootInfo (
     Cache4 = &Private->DhcpAck.Dhcp4;\r
   }\r
 \r
-  ASSERT (Cache4->OptList[PXEBC_DHCP4_TAG_INDEX_BOOTFILE] != NULL);\r
+  if (Cache4->OptList[PXEBC_DHCP4_TAG_INDEX_BOOTFILE] == NULL) {\r
+    //\r
+    // This should never happen in a correctly configured DHCP / PXE\r
+    // environment. One misconfiguration that can cause it is two DHCP servers\r
+    // mistakenly running on the same network segment at the same time, and\r
+    // racing each other in answering DHCP requests. Thus, the DHCP packets\r
+    // that the edk2 PXE client considers "belonging together" may actually be\r
+    // entirely independent, coming from two (competing) DHCP servers.\r
+    //\r
+    // Try to deal with this gracefully. Note that this check is not\r
+    // comprehensive, as we don't try to identify all such errors.\r
+    //\r
+    return EFI_PROTOCOL_ERROR;\r
+  }\r
 \r
   //\r
   // Parse the boot server address.\r
@@ -612,7 +625,20 @@ PxeBcDhcp6BootInfo (
     Cache6 = &Private->DhcpAck.Dhcp6;\r
   }\r
 \r
-  ASSERT (Cache6->OptList[PXEBC_DHCP6_IDX_BOOT_FILE_URL] != NULL);\r
+  if (Cache6->OptList[PXEBC_DHCP6_IDX_BOOT_FILE_URL] == NULL) {\r
+    //\r
+    // This should never happen in a correctly configured DHCP / PXE\r
+    // environment. One misconfiguration that can cause it is two DHCP servers\r
+    // mistakenly running on the same network segment at the same time, and\r
+    // racing each other in answering DHCP requests. Thus, the DHCP packets\r
+    // that the edk2 PXE client considers "belonging together" may actually be\r
+    // entirely independent, coming from two (competing) DHCP servers.\r
+    //\r
+    // Try to deal with this gracefully. Note that this check is not\r
+    // comprehensive, as we don't try to identify all such errors.\r
+    //\r
+    return EFI_PROTOCOL_ERROR;\r
+  }\r
 \r
   //\r
   // Set the station address to IP layer.\r