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206 • Linux Symposium 2004 • Volume One In kcompat code, translate to legacy kernel API: #if ( LINUX_VERSION_CODE < \ KERNEL_VERSION(2,4,22) ) #define pci_name(x) ((x)->slot_name) #endif #ifndef HAVE_FREE_NETDEV #define free_netdev(x) kfree(x) #endif Guideline #7: Plan to Re-write the Driver at Least Once You will not get it right the first time. Plan on rewriting the driver from scratch at least once. This will cleanse the code, removing dead code and organizing/consolidating functionality. For example, the last e100 re-write reduced the driver size by 75% without loss of functionality. Conclusion Following these guidelines will result in more maintainable device drivers with better acceptance into the Linux kernel tree. The basic idea is to remove as much as possible from the driver without loss of functionality. References • The latest e100 driver code is available at linux/driver/net/e100.c (2.6.4 kernel or higher). • An example of kcompat is here: http://sf.net/projects/ gkernel
NFSv4 and rpcsec_gss for linux J. Bruce Fields University of Michigan bfields@umich.edu Abstract The 2.6 Linux kernels now include support for version 4 of NFS. In addition to built-in locking and ACL support, and features designed to improve performance over the Internet, NFSv4 also mandates the implementation of strong cryptographic security. This security is provided by rpcsec_gss, a standard, widely implemented protocol that operates at the rpc level, and hence can also provide security for NFS versions 2 and 3. 1 The rpcsec_gss protocol The rpc protocol, which all version of NFS and related protocols are built upon, includes generic support for authentication mechanisms: each rpc call has two fields, the credential and the verifier, each consisting of a 32-bit integer, designating a “security flavor,” followed by 400 bytes of opaque data whose structure depends on the specified flavor. Similarly, each reply includes a single “verifier.” Until recently, the only widely implemented security flavor has been the auth_unix flavor, which uses the credential to pass uid’s and gid’s and simply asks the server to trust them. This may be satisfactory given physical security over the clients and the network, but for many situations (including use over the Internet), it is inadequate. Thus rfc 2203 defines the rpcsec_gss protocol, which uses rpc’s opaque security fields to carry cryptographically secure tokens. The cryptographic services are provided by the GSS-API (“Generic Security Service Application Program Interface,” defined by rfc 2743), allowing the use of a wide variety of security mechanisms, including, for example, Kerberos. Three levels of security are provided by rpcsec_gss: 1. Authentication only: The rpc header of each request and response is signed. 2. Integrity: The header and body of each request and response is signed. 3. Privacy: The header of each request is signed, and the body is encrypted. The combination of a security level with a GSS-API mechanism can be designated by a 32-bit “pseudoflavor.” The mount protocol used with NFS versions 2 and 3 uses a list of pseudoflavors to communicate the security capabilities of a server. NFSv4 does not use pseudoflavors on the wire, but they are still useful in internal interfaces. Security protocols generally require some initial negotiation, to determine the capabilities of the systems involved and to choose session keys. The rpcsec_gss protocol uses calls with procedure number 0 for this purpose. Normally such a call is a simple “ping” with no side-effects, useful for measuring round-trip
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Proceedings of the Linux Symposium
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The State of ACPI in the Linux Kern
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Conference Organizers Andrew J. Hut
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TCP Connection Passing Werner Almes
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Linux Symposium 2004 • Volume One
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Cooperative Linux Dan Aloni da-x@co
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Build your own Wireless Access Poin
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Run-time testing of LSB Application
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Linux Block IO—present and future
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Linux AIO Performance and Robustnes
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Methods to Improve Bootup Time in L
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Linux on NUMA Systems Martin J. Bli
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Improving Kernel Performance by Unm
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Linux Virtualization on IBM POWER5
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The State of ACPI in the Linux Kern
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Scaling Linux® to the Extreme From
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Get More Device Drivers out of the
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Hotplug Memory and the Linux VM Dav
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