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refactor(fsthttp,abi/fastly): right-size and adapt buffers
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Does not modify the values of Limits fields.
The Header-related fields are still used by the Limits API.
Though the fields are unexported, their values are exposed through the exported methods.
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@cee-dub
cee-dub committed Jun 13, 2024
1 parent 7fc7e49 commit a9a66ea
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Showing 4 changed files with 80 additions and 91 deletions.
8 changes: 4 additions & 4 deletions fsthttp/request.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,10 +17,10 @@ import (

// RequestLimits are the limits for the components of an HTTP request.
var RequestLimits = Limits{
maxHeaderNameLen: fastly.DefaultMaxHeaderNameLen,
maxHeaderValueLen: fastly.DefaultMaxHeaderValueLen,
maxMethodLen: fastly.DefaultMaxMethodLen,
maxURLLen: fastly.DefaultMaxURLLen,
maxHeaderNameLen: fastly.DefaultLargeBufLen,
maxHeaderValueLen: fastly.DefaultLargeBufLen,
maxMethodLen: fastly.DefaultMediumBufLen,
maxURLLen: fastly.DefaultLargeBufLen,
}

// Request represents an HTTP request received by this server from a requesting
Expand Down
4 changes: 2 additions & 2 deletions fsthttp/response.go
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,8 @@ import (

// ResponseLimits are the limits for the components of an HTTP response.
var ResponseLimits = Limits{
maxHeaderNameLen: fastly.DefaultMaxHeaderNameLen,
maxHeaderValueLen: fastly.DefaultMaxHeaderValueLen,
maxHeaderNameLen: fastly.DefaultLargeBufLen,
maxHeaderValueLen: fastly.DefaultLargeBufLen,
}

// Response to an outgoing HTTP request made by this server.
Expand Down
140 changes: 68 additions & 72 deletions internal/abi/fastly/hostcalls_guest.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -531,14 +531,14 @@ func (r *HTTPRequest) SetCacheOverride(options CacheOverrideOptions) error {
//go:wasmimport fastly_http_req downstream_client_ip_addr
//go:noescape
func fastlyHTTPReqDownstreamClientIPAddr(
addrOctetsOut prim.Pointer[prim.Char8], // must be 16-byte array
addrOctetsOut prim.Pointer[prim.Char8], // ipBufLen is 16 bytes
nwrittenOut prim.Pointer[prim.Usize],
) FastlyStatus

// DownstreamClientIPAddr returns the IP address of the downstream client that
// performed the singleton downstream request.
func DownstreamClientIPAddr() (net.IP, error) {
buf := prim.NewWriteBuffer(16) // must be a 16-byte array
buf := prim.NewWriteBuffer(ipBufLen)

if err := fastlyHTTPReqDownstreamClientIPAddr(
prim.ToPointer(buf.Char8Pointer()),
Expand Down Expand Up @@ -570,7 +570,8 @@ func fastlyHTTPReqDownstreamTLSCipherOpenSSLName(
// DownstreamTLSCipherOpenSSLName returns the name of the OpenSSL TLS cipher
// used with the singleton downstream request, if any.
func DownstreamTLSCipherOpenSSLName() (string, error) {
buf := prim.NewWriteBuffer(defaultBufferLen)
// https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-cipher/
buf := prim.NewWriteBuffer(DefaultSmallBufLen) // Longest (49) = TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256_OLD

if err := fastlyHTTPReqDownstreamTLSCipherOpenSSLName(
prim.ToPointer(buf.Char8Pointer()),
Expand Down Expand Up @@ -603,7 +604,8 @@ func fastlyHTTPReqDownstreamTLSProtocol(
// DownstreamTLSProtocol returns the name of the TLS protocol used with the
// singleton downstream request, if any.
func DownstreamTLSProtocol() (string, error) {
buf := prim.NewWriteBuffer(defaultBufferLen)
// https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-protocol/
buf := prim.NewWriteBuffer(DefaultSmallBufLen) // Longest (~8) = TLSv1.2

if err := fastlyHTTPReqDownstreamTLSProtocol(
prim.ToPointer(buf.Char8Pointer()),
Expand Down Expand Up @@ -636,13 +638,19 @@ func fastlyHTTPReqDownstreamTLSClientHello(
// DownstreamTLSClientHello returns the ClientHello message sent by the client
// in the singleton downstream request, if any.
func DownstreamTLSClientHello() ([]byte, error) {
buf := prim.NewWriteBuffer(defaultBufferLen)

if err := fastlyHTTPReqDownstreamTLSClientHello(
n := DefaultLargeBufLen
alloc:
buf := prim.NewWriteBuffer(n) // Longest (~132,000); typically < 2^14; RFC https://datatracker.ietf.org/doc/html/rfc8446#section-4.1.2
status := fastlyHTTPReqDownstreamTLSClientHello(
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
).toError(); err != nil {
)
if status == FastlyStatusBufLen && buf.NValue() > 0 {
n = int(buf.NValue())
goto alloc // avoid all the allocations of a new stack, etc.
}
if err := status.toError(); err != nil {
return nil, err
}

Expand Down Expand Up @@ -1022,7 +1030,7 @@ func fastlyHTTPReqMethodGet(

// GetMethod returns the HTTP method of the request.
func (r *HTTPRequest) GetMethod() (string, error) {
n := DefaultMaxMethodLen
n := DefaultSmallBufLen
alloc:
buf := prim.NewWriteBuffer(n)
status := fastlyHTTPReqMethodGet(
Expand Down Expand Up @@ -1088,7 +1096,7 @@ func fastlyHTTPReqURIGet(

// GetURI returns the fully qualified URI of the request.
func (r *HTTPRequest) GetURI() (string, error) {
n := DefaultMaxURLLen
n := DefaultMediumBufLen // Longest (unknown); Typically less than 1024, but some browsers accept much longer
alloc:
buf := prim.NewWriteBuffer(n)
status := fastlyHTTPReqURIGet(
Expand Down Expand Up @@ -1679,21 +1687,21 @@ func fastlyBackendGetHost(nameData prim.Pointer[prim.U8], nameLen prim.Usize,
) FastlyStatus

func BackendGetHost(name string) (string, error) {
hostBuf := prim.NewWriteBuffer(defaultBufferLen)
buf := prim.NewWriteBuffer(dnsBufLen) // Longest (255) by DNS RFCs https://datatracker.ietf.org/doc/html/rfc2181#section-11

nameBuffer := prim.NewReadBufferFromString(name).Wstring()

if err := fastlyBackendGetHost(
nameBuffer.Data, nameBuffer.Len,

prim.ToPointer(hostBuf.Char8Pointer()),
hostBuf.Cap(),
prim.ToPointer(hostBuf.NPointer()),
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
).toError(); err != nil {
return "", err
}

return hostBuf.ToString(), nil
return buf.ToString(), nil
}

// witx:
Expand All @@ -1715,20 +1723,20 @@ func fastlyBackendGetOverrideHost(nameData prim.Pointer[prim.U8], nameLen prim.U
) FastlyStatus

func BackendGetOverrideHost(name string) (string, error) {
hostBuf := prim.NewWriteBuffer(defaultBufferLen)
buf := prim.NewWriteBuffer(dnsBufLen) // Longest (255) by DNS RFCs https://datatracker.ietf.org/doc/html/rfc2181#section-11

nameBuffer := prim.NewReadBufferFromString(name).Wstring()

if err := fastlyBackendGetOverrideHost(
nameBuffer.Data, nameBuffer.Len,
prim.ToPointer(hostBuf.Char8Pointer()),
hostBuf.Cap(),
prim.ToPointer(hostBuf.NPointer()),
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
).toError(); err != nil {
return "", err
}

return hostBuf.ToString(), nil
return buf.ToString(), nil
}

// witx:
Expand Down Expand Up @@ -2471,16 +2479,24 @@ func fastlyDictionaryGet(

// Get the value for key, as a byte slice, if it exists.
func (d *Dictionary) GetBytes(key string) ([]byte, error) {
buf := prim.NewWriteBuffer(dictionaryValueMaxLen)
keyBuffer := prim.NewReadBufferFromString(key).Wstring()

if err := fastlyDictionaryGet(
n := DefaultMediumBufLen // Longest (8192) = Config Store limit; typical values likely less than 1024
alloc:
buf := prim.NewWriteBuffer(n)
status := fastlyDictionaryGet(
d.h,
keyBuffer.Data, keyBuffer.Len,
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
).toError(); err != nil {
)
if status == FastlyStatusBufLen && buf.NValue() > 0 {
n = int(buf.NValue())
goto alloc // avoid all the allocations of a new stack, etc.
}

if err := status.toError(); err != nil {
return nil, err
}

Expand Down Expand Up @@ -2549,19 +2565,26 @@ func fastlyGeoLookup(

// GeoLookup returns the geographic data associated with the IP address.
func GeoLookup(ip net.IP) ([]byte, error) {
buf := prim.NewWriteBuffer(1024) // initial geo buf size
if x := ip.To4(); x != nil {
ip = x
}
addrOctets := prim.NewReadBufferFromBytes(ip)

if err := fastlyGeoLookup(
n := DefaultMediumBufLen
alloc:
buf := prim.NewWriteBuffer(n) // initial geo buf size
status := fastlyGeoLookup(
prim.ToPointer(addrOctets.Char8Pointer()),
addrOctets.Len(),
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
).toError(); err != nil {
)
if status == FastlyStatusBufLen && buf.NValue() > 0 {
n = int(buf.NValue())
goto alloc // avoid all the allocations of a new stack, etc.
}
if err := status.toError(); err != nil {
return nil, err
}

Expand Down Expand Up @@ -2827,35 +2850,24 @@ func (st *SecretStore) Get(name string) (*Secret, error) {
//go:noescape
func fastlySecretPlaintext(
h secretHandle,
buf prim.Pointer[prim.Char8],
bufLen prim.Usize,
buf prim.Pointer[prim.Char8], bufLen prim.Usize,
nwritten prim.Pointer[prim.Usize],
) FastlyStatus

// Plaintext decrypts and returns the secret value as a byte slice.
func (s *Secret) Plaintext() ([]byte, error) {
// Most secrets will fit into the initial secret buffer size, so
// we'll start with that. If it doesn't fit, we'll know the exact
// size of the buffer to try again.
buf := prim.NewWriteBuffer(initialSecretLen)

n := DefaultMediumBufLen
alloc:
buf := prim.NewWriteBuffer(n)
status := fastlySecretPlaintext(
s.h,
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
)
if status == FastlyStatusBufLen {
// The buffer was too small, but it'll tell us how big it will
// need to be in order to fit the plaintext.
buf = prim.NewWriteBuffer(int(buf.NValue()))

status = fastlySecretPlaintext(
s.h,
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
)
if status == FastlyStatusBufLen && buf.NValue() > 0 {
n = int(buf.NValue())
goto alloc // avoid all the allocations of a new stack, etc.
}

if err := status.toError(); err != nil {
Expand Down Expand Up @@ -3298,27 +3310,19 @@ func fastlyCacheGetUserMetadata(
) FastlyStatus

func (c *CacheEntry) UserMetadata() ([]byte, error) {
buf := prim.NewWriteBuffer(defaultBufferLen)

n := DefaultSmallBufLen
alloc:
buf := prim.NewWriteBuffer(n) // Longest (unknown)
status := fastlyCacheGetUserMetadata(
c.h,
prim.ToPointer(buf.U8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
)
if status == FastlyStatusBufLen {
// The buffer was too small, but it'll tell us how big it will
// need to be in order to fit the content.
buf = prim.NewWriteBuffer(int(buf.NValue()))

status = fastlyCacheGetUserMetadata(
c.h,
prim.ToPointer(buf.U8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
)
if status == FastlyStatusBufLen && buf.NValue() > 0 {
n = int(buf.NValue())
goto alloc // avoid all the allocations of a new stack, etc.
}

if err := status.toError(); err != nil {
return nil, err
}
Expand Down Expand Up @@ -3541,27 +3545,19 @@ func fastlyDeviceDetectionLookup(
) FastlyStatus

func DeviceLookup(userAgent string) ([]byte, error) {
buf := prim.NewWriteBuffer(defaultBufferLen)

userAgentBuffer := prim.NewReadBufferFromString(userAgent).Wstring()

n := DefaultSmallBufLen // Longest JSON of https://www.fastly.com/documentation/reference/vcl/variables/client-request/client-identified/
alloc:
buf := prim.NewWriteBuffer(n)
status := fastlyDeviceDetectionLookup(
userAgentBuffer.Data, userAgentBuffer.Len,
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
)
if status == FastlyStatusBufLen {
// The buffer was too small, but it'll tell us how big it will
// need to be in order to fit the content.
buf = prim.NewWriteBuffer(int(buf.NValue()))

status = fastlyDeviceDetectionLookup(
userAgentBuffer.Data, userAgentBuffer.Len,
prim.ToPointer(buf.Char8Pointer()),
buf.Cap(),
prim.ToPointer(buf.NPointer()),
)
if status == FastlyStatusBufLen && buf.NValue() > 0 {
n = int(buf.NValue())
goto alloc // avoid all the allocations of a new stack, etc.
}
if err := status.toError(); err != nil {
return nil, err
Expand Down
19 changes: 6 additions & 13 deletions internal/abi/fastly/types.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -316,19 +316,12 @@ const (
)

const (
// DefaultMaxHeaderNameLen is the default header name length limit
DefaultMaxHeaderNameLen = 8192
// DefaultMaxHeaderValueLen is the default header value length limit
DefaultMaxHeaderValueLen = 8192
// DefaultMaxMethodLen is the default method length limit
DefaultMaxMethodLen = 1024
// DefaultMaxURLLen is the default URL length limit
DefaultMaxURLLen = 8192

dictionaryValueMaxLen = 8192 // https://docs.fastly.com/en/guides/about-edge-dictionaries#limitations-and-considerations
defaultBufferLen = 16 * 1024

initialSecretLen = 1024
ipBufLen = 16 // known size for IP address buffers
dnsBufLen = 256 // known size for "DNS" values, enough to hold the longest possible hostname or domain name

DefaultSmallBufLen = 128 // default size for "typically-small" values with variable sizes: HTTP methods, header names, tls protocol names, cipher suites
DefaultMediumBufLen = 1024 // default size for values between small and large with variable sizes
DefaultLargeBufLen = 8192 // default size for "typically-large" values with variable sizes; header values, URLs.
)

// CacheOverrideOptions collects specific, caching-related options for outbound
Expand Down

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