cloud_init: fix errors when loaded before acquiring IP address #1992
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Attempting to connect to a cloud_init server before an IP address is acquired via DHCP results in a connection error, which causes the cloud_init klib to fail to initialize (and thus the VM to be stopped without executing the user program). This change fixes the above issue by adding a check for a suitable IP address configuration before attempting to connect to a server or resolve its host name, and retrying connecting at a later time if this check fails. The code to retry a connection when the DNS query function returns ERR_INPROGRESS has been removed, and a call to cloud_download_connect() has been added in the DNS callback function, because otherwise a large delay in the DNS resolution process may cause many DNS reuests to be pending at the same time, which can result in a DNS query error (and subsequent klib initialization failure) due to unavailable free request slots. The code that checks for ERR_VAL (which had been added to retry the connection if no IP address has been acquired) has been removed because it no longer works (now the kernel sets up a default DNS server during initialization, therefore the ERR_VAL value is never returned). The "exec_wait_for_ip4_secs" manifest flag has been removed because it does not serve its intended purpose to delay klib initialization (this flag can only delay execution of the user program).
eyberg
approved these changes
Jan 19, 2024
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Attempting to connect to a cloud_init server before an IP address is acquired via DHCP results in a connection error, which causes the cloud_init klib to fail to initialize (and thus the VM to be stopped without executing the user program). This is causing sporadic "program startup failed before exec: (result:connect failed (-4))" errors to occur when running the cloud_init e2e test as part of the Jenkins CI tests.
This change fixes the above issue by adding a check for a suitable IP address configuration before attempting to connect to a server or resolve its host name, and retrying connecting at a later time if this check fails.
The code to retry a connection when the DNS query function returns ERR_INPROGRESS has been removed, and a call to
cloud_download_connect() has been added in the DNS callback function, because otherwise a large delay in the DNS resolution process may cause many DNS requests to be pending at the same time, which can result in a DNS query error (and subsequent klib initialization failure) due to unavailable free request slots. The code that checks for ERR_VAL (which had been added to retry the connection if no IP address has been acquired) has been removed because it no longer works (now the kernel sets up a default DNS server during initialization, therefore the ERR_VAL value is never returned).
The "exec_wait_for_ip4_secs" manifest flag has been removed because it does not serve its intended purpose to delay klib initialization (this flag can only delay execution of the user program).