[http] Allow for HTTPS-only builds

Separate out the core HTTP functionality (which is shared by both HTTP
and HTTPS) from the provision of the "http://" URI opener.  This
allows for builds that support only "https://" URIs.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/errfile.h

@@ -161,7 +161,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define ERRFILE_nullnet			( ERRFILE_NET | 0x00090000 )
 #define ERRFILE_tcp			( ERRFILE_NET | 0x000a0000 )
 #define ERRFILE_ftp			( ERRFILE_NET | 0x000b0000 )
-#define ERRFILE_http			( ERRFILE_NET | 0x000c0000 )
+#define ERRFILE_httpcore		( ERRFILE_NET | 0x000c0000 )
 #define ERRFILE_iscsi			( ERRFILE_NET | 0x000d0000 )
 #define ERRFILE_tcpip			( ERRFILE_NET | 0x000e0000 )
 #define ERRFILE_udp			( ERRFILE_NET | 0x000f0000 )

src/net/tcp/http.c

@@ -25,869 +25,13 @@ FILE_LICENCE ( GPL2_OR_LATER );
  *
  */
 
-#include <stdint.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <string.h>
-#include <strings.h>
-#include <byteswap.h>
-#include <errno.h>
-#include <assert.h>
-#include <ipxe/uri.h>
-#include <ipxe/refcnt.h>
-#include <ipxe/iobuf.h>
-#include <ipxe/xfer.h>
+#include <stddef.h>
 #include <ipxe/open.h>
-#include <ipxe/socket.h>
-#include <ipxe/tcpip.h>
-#include <ipxe/process.h>
-#include <ipxe/linebuf.h>
-#include <ipxe/features.h>
-#include <ipxe/base64.h>
-#include <ipxe/blockdev.h>
-#include <ipxe/acpi.h>
 #include <ipxe/http.h>
+#include <ipxe/features.h>
 
 FEATURE ( FEATURE_PROTOCOL, "HTTP", DHCP_EB_FEATURE_HTTP, 1 );
 
-/** Block size used for HTTP block device request */
-#define HTTP_BLKSIZE 512
-
-/** HTTP flags */
-enum http_flags {
-	/** Request is waiting to be transmitted */
-	HTTP_TX_PENDING = 0x0001,
-	/** Fetch header only */
-	HTTP_HEAD_ONLY = 0x0002,
-	/** Keep connection alive */
-	HTTP_KEEPALIVE = 0x0004,
-};
-
-/** HTTP receive state */
-enum http_rx_state {
-	HTTP_RX_RESPONSE = 0,
-	HTTP_RX_HEADER,
-	HTTP_RX_CHUNK_LEN,
-	HTTP_RX_DATA,
-	HTTP_RX_TRAILER,
-	HTTP_RX_IDLE,
-	HTTP_RX_DEAD,
-};
-
-/**
- * An HTTP request
- *
- */
-struct http_request {
-	/** Reference count */
-	struct refcnt refcnt;
-	/** Data transfer interface */
-	struct interface xfer;
-	/** Partial transfer interface */
-	struct interface partial;
-
-	/** URI being fetched */
-	struct uri *uri;
-	/** Transport layer interface */
-	struct interface socket;
-
-	/** Flags */
-	unsigned int flags;
-	/** Starting offset of partial transfer (if applicable) */
-	size_t partial_start;
-	/** Length of partial transfer (if applicable) */
-	size_t partial_len;
-
-	/** TX process */
-	struct process process;
-
-	/** RX state */
-	enum http_rx_state rx_state;
-	/** Received length */
-	size_t rx_len;
-	/** Length remaining (or 0 if unknown) */
-	size_t remaining;
-	/** HTTP is using Transfer-Encoding: chunked */
-	int chunked;
-	/** Current chunk length remaining (if applicable) */
-	size_t chunk_remaining;
-	/** Line buffer for received header lines */
-	struct line_buffer linebuf;
-	/** Receive data buffer (if applicable) */
-	userptr_t rx_buffer;
-};
-
-/**
- * Free HTTP request
- *
- * @v refcnt		Reference counter
- */
-static void http_free ( struct refcnt *refcnt ) {
-	struct http_request *http =
-		container_of ( refcnt, struct http_request, refcnt );
-
-	uri_put ( http->uri );
-	empty_line_buffer ( &http->linebuf );
-	free ( http );
-};
-
-/**
- * Close HTTP request
- *
- * @v http		HTTP request
- * @v rc		Return status code
- */
-static void http_close ( struct http_request *http, int rc ) {
-
-	/* Prevent further processing of any current packet */
-	http->rx_state = HTTP_RX_DEAD;
-
-	/* If we had a Content-Length, and the received content length
-	 * isn't correct, flag an error
-	 */
-	if ( http->remaining != 0 ) {
-		DBGC ( http, "HTTP %p incorrect length %zd, should be %zd\n",
-		       http, http->rx_len, ( http->rx_len + http->remaining ) );
-		if ( rc == 0 )
-			rc = -EIO;
-	}
-
-	/* Remove process */
-	process_del ( &http->process );
-
-	/* Close all data transfer interfaces */
-	intf_shutdown ( &http->socket, rc );
-	intf_shutdown ( &http->partial, rc );
-	intf_shutdown ( &http->xfer, rc );
-}
-
-/**
- * Mark HTTP request as completed successfully
- *
- * @v http		HTTP request
- */
-static void http_done ( struct http_request *http ) {
-
-	/* If we had a Content-Length, and the received content length
-	 * isn't correct, force an error
-	 */
-	if ( http->remaining != 0 ) {
-		http_close ( http, -EIO );
-		return;
-	}
-
-	/* Enter idle state */
-	http->rx_state = HTTP_RX_IDLE;
-	http->rx_len = 0;
-	assert ( http->remaining == 0 );
-	assert ( http->chunked == 0 );
-	assert ( http->chunk_remaining == 0 );
-
-	/* Close partial transfer interface */
-	intf_restart ( &http->partial, 0 );
-
-	/* Close everything unless we are keeping the connection alive */
-	if ( ! ( http->flags & HTTP_KEEPALIVE ) )
-		http_close ( http, 0 );
-}
-
-/**
- * Convert HTTP response code to return status code
- *
- * @v response		HTTP response code
- * @ret rc		Return status code
- */
-static int http_response_to_rc ( unsigned int response ) {
-	switch ( response ) {
-	case 200:
-	case 206:
-	case 301:
-	case 302:
-		return 0;
-	case 404:
-		return -ENOENT;
-	case 403:
-		return -EPERM;
-	case 401:
-		return -EACCES;
-	default:
-		return -EIO;
-	}
-}
-
-/**
- * Handle HTTP response
- *
- * @v http		HTTP request
- * @v response		HTTP response
- * @ret rc		Return status code
- */
-static int http_rx_response ( struct http_request *http, char *response ) {
-	char *spc;
-	unsigned int code;
-	int rc;
-
-	DBGC ( http, "HTTP %p response \"%s\"\n", http, response );
-
-	/* Check response starts with "HTTP/" */
-	if ( strncmp ( response, "HTTP/", 5 ) != 0 )
-		return -EIO;
-
-	/* Locate and check response code */
-	spc = strchr ( response, ' ' );
-	if ( ! spc )
-		return -EIO;
-	code = strtoul ( spc, NULL, 10 );
-	if ( ( rc = http_response_to_rc ( code ) ) != 0 )
-		return rc;
-
-	/* Move to received headers */
-	http->rx_state = HTTP_RX_HEADER;
-	return 0;
-}
-
-/**
- * Handle HTTP Location header
- *
- * @v http		HTTP request
- * @v value		HTTP header value
- * @ret rc		Return status code
- */
-static int http_rx_location ( struct http_request *http, const char *value ) {
-	int rc;
-
-	/* Redirect to new location */
-	DBGC ( http, "HTTP %p redirecting to %s\n", http, value );
-	if ( ( rc = xfer_redirect ( &http->xfer, LOCATION_URI_STRING,
-				    value ) ) != 0 ) {
-		DBGC ( http, "HTTP %p could not redirect: %s\n",
-		       http, strerror ( rc ) );
-		return rc;
-	}
-
-	return 0;
-}
-
-/**
- * Handle HTTP Content-Length header
- *
- * @v http		HTTP request
- * @v value		HTTP header value
- * @ret rc		Return status code
- */
-static int http_rx_content_length ( struct http_request *http,
-				    const char *value ) {
-	struct block_device_capacity capacity;
-	size_t content_len;
-	char *endp;
-
-	/* Parse content length */
-	content_len = strtoul ( value, &endp, 10 );
-	if ( *endp != '\0' ) {
-		DBGC ( http, "HTTP %p invalid Content-Length \"%s\"\n",
-		       http, value );
-		return -EIO;
-	}
-
-	/* If we already have an expected content length, and this
-	 * isn't it, then complain
-	 */
-	if ( http->remaining && ( http->remaining != content_len ) ) {
-		DBGC ( http, "HTTP %p incorrect Content-Length %zd (expected "
-		       "%zd)\n", http, content_len, http->remaining );
-		return -EIO;
-	}
-	if ( ! ( http->flags & HTTP_HEAD_ONLY ) )
-		http->remaining = content_len;
-
-	/* Use seek() to notify recipient of filesize */
-	xfer_seek ( &http->xfer, http->remaining );
-	xfer_seek ( &http->xfer, 0 );
-
-	/* Report block device capacity if applicable */
-	if ( http->flags & HTTP_HEAD_ONLY ) {
-		capacity.blocks = ( content_len / HTTP_BLKSIZE );
-		capacity.blksize = HTTP_BLKSIZE;
-		capacity.max_count = -1U;
-		block_capacity ( &http->partial, &capacity );
-	}
-	return 0;
-}
-
-/**
- * Handle HTTP Transfer-Encoding header
- *
- * @v http		HTTP request
- * @v value		HTTP header value
- * @ret rc		Return status code
- */
-static int http_rx_transfer_encoding ( struct http_request *http,
-				       const char *value ) {
-
-	if ( strcmp ( value, "chunked" ) == 0 ) {
-		/* Mark connection as using chunked transfer encoding */
-		http->chunked = 1;
-	}
-
-	return 0;
-}
-
-/** An HTTP header handler */
-struct http_header_handler {
-	/** Name (e.g. "Content-Length") */
-	const char *header;
-	/** Handle received header
-	 *
-	 * @v http	HTTP request
-	 * @v value	HTTP header value
-	 * @ret rc	Return status code
-	 *
-	 * If an error is returned, the download will be aborted.
-	 */
-	int ( * rx ) ( struct http_request *http, const char *value );
-};
-
-/** List of HTTP header handlers */
-static struct http_header_handler http_header_handlers[] = {
-	{
-		.header = "Location",
-		.rx = http_rx_location,
-	},
-	{
-		.header = "Content-Length",
-		.rx = http_rx_content_length,
-	},
-	{
-		.header = "Transfer-Encoding",
-		.rx = http_rx_transfer_encoding,
-	},
-	{ NULL, NULL }
-};
-
-/**
- * Handle HTTP header
- *
- * @v http		HTTP request
- * @v header		HTTP header
- * @ret rc		Return status code
- */
-static int http_rx_header ( struct http_request *http, char *header ) {
-	struct http_header_handler *handler;
-	char *separator;
-	char *value;
-	int rc;
-
-	/* An empty header line marks the end of this phase */
-	if ( ! header[0] ) {
-		empty_line_buffer ( &http->linebuf );
-		if ( ( http->rx_state == HTTP_RX_HEADER ) &&
-		     ( ! ( http->flags & HTTP_HEAD_ONLY ) ) ) {
-			DBGC ( http, "HTTP %p start of data\n", http );
-			http->rx_state = ( http->chunked ?
-					   HTTP_RX_CHUNK_LEN : HTTP_RX_DATA );
-			return 0;
-		} else {
-			DBGC ( http, "HTTP %p end of trailer\n", http );
-			http_done ( http );
-			return 0;
-		}
-	}
-
-	DBGC ( http, "HTTP %p header \"%s\"\n", http, header );
-
-	/* Split header at the ": " */
-	separator = strstr ( header, ": " );
-	if ( ! separator ) {
-		DBGC ( http, "HTTP %p malformed header\n", http );
-		return -EIO;
-	}
-	*separator = '\0';
-	value = ( separator + 2 );
-
-	/* Hand off to header handler, if one exists */
-	for ( handler = http_header_handlers ; handler->header ; handler++ ) {
-		if ( strcasecmp ( header, handler->header ) == 0 ) {
-			if ( ( rc = handler->rx ( http, value ) ) != 0 )
-				return rc;
-			break;
-		}
-	}
-	return 0;
-}
-
-/**
- * Handle HTTP chunk length
- *
- * @v http		HTTP request
- * @v length		HTTP chunk length
- * @ret rc		Return status code
- */
-static int http_rx_chunk_len ( struct http_request *http, char *length ) {
-	char *endp;
-
-	/* Skip blank lines between chunks */
-	if ( length[0] == '\0' )
-		return 0;
-
-	/* Parse chunk length */
-	http->chunk_remaining = strtoul ( length, &endp, 16 );
-	if ( *endp != '\0' ) {
-		DBGC ( http, "HTTP %p invalid chunk length \"%s\"\n",
-		       http, length );
-		return -EIO;
-	}
-
-	/* Terminate chunked encoding if applicable */
-	if ( http->chunk_remaining == 0 ) {
-		DBGC ( http, "HTTP %p end of chunks\n", http );
-		http->chunked = 0;
-		http->rx_state = HTTP_RX_TRAILER;
-		return 0;
-	}
-
-	/* Use seek() to notify recipient of new filesize */
-	DBGC ( http, "HTTP %p start of chunk of length %zd\n",
-	       http, http->chunk_remaining );
-	xfer_seek ( &http->xfer, ( http->rx_len + http->chunk_remaining ) );
-	xfer_seek ( &http->xfer, http->rx_len );
-
-	/* Start receiving data */
-	http->rx_state = HTTP_RX_DATA;
-
-	return 0;
-}
-
-/** An HTTP line-based data handler */
-struct http_line_handler {
-	/** Handle line
-	 *
-	 * @v http	HTTP request
-	 * @v line	Line to handle
-	 * @ret rc	Return status code
-	 */
-	int ( * rx ) ( struct http_request *http, char *line );
-};
-
-/** List of HTTP line-based data handlers */
-static struct http_line_handler http_line_handlers[] = {
-	[HTTP_RX_RESPONSE]	= { .rx = http_rx_response },
-	[HTTP_RX_HEADER]	= { .rx = http_rx_header },
-	[HTTP_RX_CHUNK_LEN]	= { .rx = http_rx_chunk_len },
-	[HTTP_RX_TRAILER]	= { .rx = http_rx_header },
-};
-
-/**
- * Handle new data arriving via HTTP connection
- *
- * @v http		HTTP request
- * @v iobuf		I/O buffer
- * @v meta		Data transfer metadata
- * @ret rc		Return status code
- */
-static int http_socket_deliver ( struct http_request *http,
-				 struct io_buffer *iobuf,
-				 struct xfer_metadata *meta __unused ) {
-	struct http_line_handler *lh;
-	char *line;
-	size_t data_len;
-	ssize_t line_len;
-	int rc = 0;
-
-	while ( iobuf && iob_len ( iobuf ) ) {
-
-		switch ( http->rx_state ) {
-		case HTTP_RX_IDLE:
-			/* Receiving any data in this state is an error */
-			DBGC ( http, "HTTP %p received %zd bytes while %s\n",
-			       http, iob_len ( iobuf ),
-			       ( ( http->rx_state == HTTP_RX_IDLE ) ?
-				 "idle" : "dead" ) );
-			rc = -EPROTO;
-			goto done;
-		case HTTP_RX_DEAD:
-			/* Do no further processing */
-			goto done;
-		case HTTP_RX_DATA:
-			/* Pass received data to caller */
-			data_len = iob_len ( iobuf );
-			if ( http->chunk_remaining &&
-			     ( http->chunk_remaining < data_len ) ) {
-				data_len = http->chunk_remaining;
-			}
-			if ( http->remaining &&
-			     ( http->remaining < data_len ) ) {
-				data_len = http->remaining;
-			}
-			if ( http->rx_buffer != UNULL ) {
-				/* Copy to partial transfer buffer */
-				copy_to_user ( http->rx_buffer, http->rx_len,
-					       iobuf->data, data_len );
-				iob_pull ( iobuf, data_len );
-			} else if ( data_len < iob_len ( iobuf ) ) {
-				/* Deliver partial buffer as raw data */
-				rc = xfer_deliver_raw ( &http->xfer,
-							iobuf->data, data_len );
-				iob_pull ( iobuf, data_len );
-				if ( rc != 0 )
-					goto done;
-			} else {
-				/* Deliver whole I/O buffer */
-				if ( ( rc = xfer_deliver_iob ( &http->xfer,
-						 iob_disown ( iobuf ) ) ) != 0 )
-					goto done;
-			}
-			http->rx_len += data_len;
-			if ( http->chunk_remaining ) {
-				http->chunk_remaining -= data_len;
-				if ( http->chunk_remaining == 0 )
-					http->rx_state = HTTP_RX_CHUNK_LEN;
-			}
-			if ( http->remaining ) {
-				http->remaining -= data_len;
-				if ( ( http->remaining == 0 ) &&
-				     ( http->rx_state == HTTP_RX_DATA ) ) {
-					http_done ( http );
-				}
-			}
-			break;
-		case HTTP_RX_RESPONSE:
-		case HTTP_RX_HEADER:
-		case HTTP_RX_CHUNK_LEN:
-		case HTTP_RX_TRAILER:
-			/* In the other phases, buffer and process a
-			 * line at a time
-			 */
-			line_len = line_buffer ( &http->linebuf, iobuf->data,
-						 iob_len ( iobuf ) );
-			if ( line_len < 0 ) {
-				rc = line_len;
-				DBGC ( http, "HTTP %p could not buffer line: "
-				       "%s\n", http, strerror ( rc ) );
-				goto done;
-			}
-			iob_pull ( iobuf, line_len );
-			line = buffered_line ( &http->linebuf );
-			if ( line ) {
-				lh = &http_line_handlers[http->rx_state];
-				if ( ( rc = lh->rx ( http, line ) ) != 0 )
-					goto done;
-			}
-			break;
-		default:
-			assert ( 0 );
-			break;
-		}
-	}
-
- done:
-	if ( rc )
-		http_close ( http, rc );
-	free_iob ( iobuf );
-	return rc;
-}
-
-/**
- * Check HTTP socket flow control window
- *
- * @v http		HTTP request
- * @ret len		Length of window
- */
-static size_t http_socket_window ( struct http_request *http __unused ) {
-
-	/* Window is always open.  This is to prevent TCP from
-	 * stalling if our parent window is not currently open.
-	 */
-	return ( ~( ( size_t ) 0 ) );
-}
-
-/**
- * HTTP process
- *
- * @v http		HTTP request
- */
-static void http_step ( struct http_request *http ) {
-	const char *host = http->uri->host;
-	const char *user = http->uri->user;
-	const char *password =
-		( http->uri->password ? http->uri->password : "" );
-	size_t user_pw_len = ( user ? ( strlen ( user ) + 1 /* ":" */ +
-					strlen ( password ) ) : 0 );
-	size_t user_pw_base64_len = base64_encoded_len ( user_pw_len );
-	uint8_t user_pw[ user_pw_len + 1 /* NUL */ ];
-	char user_pw_base64[ user_pw_base64_len + 1 /* NUL */ ];
-	int rc;
-	int request_len = unparse_uri ( NULL, 0, http->uri,
-					URI_PATH_BIT | URI_QUERY_BIT );
-	char request[ request_len + 1 /* NUL */ ];
-	char range[48]; /* Enough for two 64-bit integers in decimal */
-	int partial;
-
-	/* Do nothing if we have already transmitted the request */
-	if ( ! ( http->flags & HTTP_TX_PENDING ) )
-		return;
-
-	/* Do nothing until socket is ready */
-	if ( ! xfer_window ( &http->socket ) )
-		return;
-
-	/* Construct path?query request */
-	unparse_uri ( request, sizeof ( request ), http->uri,
-		      URI_PATH_BIT | URI_QUERY_BIT );
-
-	/* Construct authorisation, if applicable */
-	if ( user ) {
-		/* Make "user:password" string from decoded fields */
-		snprintf ( ( ( char * ) user_pw ), sizeof ( user_pw ),
-			   "%s:%s", user, password );
-
-		/* Base64-encode the "user:password" string */
-		base64_encode ( user_pw, user_pw_len, user_pw_base64 );
-	}
-
-	/* Force a HEAD request if we have nowhere to send any received data */
-	if ( ( xfer_window ( &http->xfer ) == 0 ) &&
-	     ( http->rx_buffer == UNULL ) ) {
-		http->flags |= ( HTTP_HEAD_ONLY | HTTP_KEEPALIVE );
-	}
-
-	/* Determine type of request */
-	partial = ( http->partial_len != 0 );
-	snprintf ( range, sizeof ( range ), "%zd-%zd", http->partial_start,
-		   ( http->partial_start + http->partial_len - 1 ) );
-
-	/* Mark request as transmitted */
-	http->flags &= ~HTTP_TX_PENDING;
-
-	/* Send GET request */
-	if ( ( rc = xfer_printf ( &http->socket,
-				  "%s %s%s HTTP/1.1\r\n"
-				  "User-Agent: iPXE/" VERSION "\r\n"
-				  "Host: %s%s%s\r\n"
-				  "%s%s%s%s%s%s%s"
-				  "\r\n",
-				  ( ( http->flags & HTTP_HEAD_ONLY ) ?
-				    "HEAD" : "GET" ),
-				  ( http->uri->path ? "" : "/" ),
-				  request, host,
-				  ( http->uri->port ?
-				    ":" : "" ),
-				  ( http->uri->port ?
-				    http->uri->port : "" ),
-				  ( ( http->flags & HTTP_KEEPALIVE ) ?
-				    "Connection: Keep-Alive\r\n" : "" ),
-				  ( partial ? "Range: bytes=" : "" ),
-				  ( partial ? range : "" ),
-				  ( partial ? "\r\n" : "" ),
-				  ( user ?
-				    "Authorization: Basic " : "" ),
-				  ( user ? user_pw_base64 : "" ),
-				  ( user ? "\r\n" : "" ) ) ) != 0 ) {
-		http_close ( http, rc );
-	}
-}
-
-/**
- * Check HTTP data transfer flow control window
- *
- * @v http		HTTP request
- * @ret len		Length of window
- */
-static size_t http_xfer_window ( struct http_request *http ) {
-
-	/* New block commands may be issued only when we are idle */
-	return ( ( http->rx_state == HTTP_RX_IDLE ) ? 1 : 0 );
-}
-
-/**
- * Initiate HTTP partial read
- *
- * @v http		HTTP request
- * @v partial		Partial transfer interface
- * @v offset		Starting offset
- * @v buffer		Data buffer
- * @v len		Length
- * @ret rc		Return status code
- */
-static int http_partial_read ( struct http_request *http,
-			       struct interface *partial,
-			       size_t offset, userptr_t buffer, size_t len ) {
-
-	/* Sanity check */
-	if ( http_xfer_window ( http ) == 0 )
-		return -EBUSY;
-
-	/* Initialise partial transfer parameters */
-	http->rx_buffer = buffer;
-	http->partial_start = offset;
-	http->partial_len = len;
-	http->remaining = len;
-
-	/* Schedule request */
-	http->rx_state = HTTP_RX_RESPONSE;
-	http->flags = ( HTTP_TX_PENDING | HTTP_KEEPALIVE );
-	if ( ! len )
-		http->flags |= HTTP_HEAD_ONLY;
-	process_add ( &http->process );
-
-	/* Attach to parent interface and return */
-	intf_plug_plug ( &http->partial, partial );
-
-	return 0;
-}
-
-/**
- * Issue HTTP block device read
- *
- * @v http		HTTP request
- * @v block		Block data interface
- * @v lba		Starting logical block address
- * @v count		Number of blocks to transfer
- * @v buffer		Data buffer
- * @v len		Length of data buffer
- * @ret rc		Return status code
- */
-static int http_block_read ( struct http_request *http,
-			     struct interface *block,
-			     uint64_t lba, unsigned int count,
-			     userptr_t buffer, size_t len __unused ) {
-
-	return http_partial_read ( http, block, ( lba * HTTP_BLKSIZE ),
-				   buffer, ( count * HTTP_BLKSIZE ) );
-}
-
-/**
- * Read HTTP block device capacity
- *
- * @v http		HTTP request
- * @v block		Block data interface
- * @ret rc		Return status code
- */
-static int http_block_read_capacity ( struct http_request *http,
-				      struct interface *block ) {
-
-	return http_partial_read ( http, block, 0, 0, 0 );
-}
-
-/**
- * Describe HTTP device in an ACPI table
- *
- * @v http		HTTP request
- * @v acpi		ACPI table
- * @v len		Length of ACPI table
- * @ret rc		Return status code
- */
-static int http_acpi_describe ( struct http_request *http,
-				struct acpi_description_header *acpi,
-				size_t len ) {
-
-	DBGC ( http, "HTTP %p cannot yet describe device in an ACPI table\n",
-	       http );
-	( void ) acpi;
-	( void ) len;
-	return 0;
-}
-
-/** HTTP socket interface operations */
-static struct interface_operation http_socket_operations[] = {
-	INTF_OP ( xfer_window, struct http_request *, http_socket_window ),
-	INTF_OP ( xfer_deliver, struct http_request *, http_socket_deliver ),
-	INTF_OP ( xfer_window_changed, struct http_request *, http_step ),
-	INTF_OP ( intf_close, struct http_request *, http_close ),
-};
-
-/** HTTP socket interface descriptor */
-static struct interface_descriptor http_socket_desc =
-	INTF_DESC_PASSTHRU ( struct http_request, socket,
-			     http_socket_operations, xfer );
-
-/** HTTP partial transfer interface operations */
-static struct interface_operation http_partial_operations[] = {
-	INTF_OP ( intf_close, struct http_request *, http_close ),
-};
-
-/** HTTP partial transfer interface descriptor */
-static struct interface_descriptor http_partial_desc =
-	INTF_DESC ( struct http_request, partial, http_partial_operations );
-
-/** HTTP data transfer interface operations */
-static struct interface_operation http_xfer_operations[] = {
-	INTF_OP ( xfer_window, struct http_request *, http_xfer_window ),
-	INTF_OP ( block_read, struct http_request *, http_block_read ),
-	INTF_OP ( block_read_capacity, struct http_request *,
-		  http_block_read_capacity ),
-	INTF_OP ( intf_close, struct http_request *, http_close ),
-	INTF_OP ( acpi_describe, struct http_request *, http_acpi_describe ),
-};
-
-/** HTTP data transfer interface descriptor */
-static struct interface_descriptor http_xfer_desc =
-	INTF_DESC_PASSTHRU ( struct http_request, xfer,
-			     http_xfer_operations, socket );
-
-/** HTTP process descriptor */
-static struct process_descriptor http_process_desc =
-	PROC_DESC_ONCE ( struct http_request, process, http_step );
-
-/**
- * Initiate an HTTP connection, with optional filter
- *
- * @v xfer		Data transfer interface
- * @v uri		Uniform Resource Identifier
- * @v default_port	Default port number
- * @v filter		Filter to apply to socket, or NULL
- * @ret rc		Return status code
- */
-int http_open_filter ( struct interface *xfer, struct uri *uri,
-		       unsigned int default_port,
-		       int ( * filter ) ( struct interface *xfer,
-					  struct interface **next ) ) {
-	struct http_request *http;
-	struct sockaddr_tcpip server;
-	struct interface *socket;
-	int rc;
-
-	/* Sanity checks */
-	if ( ! uri->host )
-		return -EINVAL;
-
-	/* Allocate and populate HTTP structure */
-	http = zalloc ( sizeof ( *http ) );
-	if ( ! http )
-		return -ENOMEM;
-	ref_init ( &http->refcnt, http_free );
-	intf_init ( &http->xfer, &http_xfer_desc, &http->refcnt );
-	intf_init ( &http->partial, &http_partial_desc, &http->refcnt );
-       	http->uri = uri_get ( uri );
-	intf_init ( &http->socket, &http_socket_desc, &http->refcnt );
-	process_init ( &http->process, &http_process_desc, &http->refcnt );
-	http->flags = HTTP_TX_PENDING;
-
-	/* Open socket */
-	memset ( &server, 0, sizeof ( server ) );
-	server.st_port = htons ( uri_port ( http->uri, default_port ) );
-	socket = &http->socket;
-	if ( filter ) {
-		if ( ( rc = filter ( socket, &socket ) ) != 0 )
-			goto err;
-	}
-	if ( ( rc = xfer_open_named_socket ( socket, SOCK_STREAM,
-					     ( struct sockaddr * ) &server,
-					     uri->host, NULL ) ) != 0 )
-		goto err;
-
-	/* Attach to parent interface, mortalise self, and return */
-	intf_plug_plug ( &http->xfer, xfer );
-	ref_put ( &http->refcnt );
-	return 0;
-
- err:
-	DBGC ( http, "HTTP %p could not create request: %s\n", 
-	       http, strerror ( rc ) );
-	http_close ( http, rc );
-	ref_put ( &http->refcnt );
-	return rc;
-}
-
 /**
  * Initiate an HTTP connection
  *

src/net/tcp/httpcore.c

@@ -0,0 +1,886 @@
+/*
+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/**
+ * @file
+ *
+ * Hyper Text Transfer Protocol (HTTP) core functionality
+ *
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <strings.h>
+#include <byteswap.h>
+#include <errno.h>
+#include <assert.h>
+#include <ipxe/uri.h>
+#include <ipxe/refcnt.h>
+#include <ipxe/iobuf.h>
+#include <ipxe/xfer.h>
+#include <ipxe/open.h>
+#include <ipxe/socket.h>
+#include <ipxe/tcpip.h>
+#include <ipxe/process.h>
+#include <ipxe/linebuf.h>
+#include <ipxe/base64.h>
+#include <ipxe/blockdev.h>
+#include <ipxe/acpi.h>
+#include <ipxe/http.h>
+
+/** Block size used for HTTP block device request */
+#define HTTP_BLKSIZE 512
+
+/** HTTP flags */
+enum http_flags {
+	/** Request is waiting to be transmitted */
+	HTTP_TX_PENDING = 0x0001,
+	/** Fetch header only */
+	HTTP_HEAD_ONLY = 0x0002,
+	/** Keep connection alive */
+	HTTP_KEEPALIVE = 0x0004,
+};
+
+/** HTTP receive state */
+enum http_rx_state {
+	HTTP_RX_RESPONSE = 0,
+	HTTP_RX_HEADER,
+	HTTP_RX_CHUNK_LEN,
+	HTTP_RX_DATA,
+	HTTP_RX_TRAILER,
+	HTTP_RX_IDLE,
+	HTTP_RX_DEAD,
+};
+
+/**
+ * An HTTP request
+ *
+ */
+struct http_request {
+	/** Reference count */
+	struct refcnt refcnt;
+	/** Data transfer interface */
+	struct interface xfer;
+	/** Partial transfer interface */
+	struct interface partial;
+
+	/** URI being fetched */
+	struct uri *uri;
+	/** Transport layer interface */
+	struct interface socket;
+
+	/** Flags */
+	unsigned int flags;
+	/** Starting offset of partial transfer (if applicable) */
+	size_t partial_start;
+	/** Length of partial transfer (if applicable) */
+	size_t partial_len;
+
+	/** TX process */
+	struct process process;
+
+	/** RX state */
+	enum http_rx_state rx_state;
+	/** Received length */
+	size_t rx_len;
+	/** Length remaining (or 0 if unknown) */
+	size_t remaining;
+	/** HTTP is using Transfer-Encoding: chunked */
+	int chunked;
+	/** Current chunk length remaining (if applicable) */
+	size_t chunk_remaining;
+	/** Line buffer for received header lines */
+	struct line_buffer linebuf;
+	/** Receive data buffer (if applicable) */
+	userptr_t rx_buffer;
+};
+
+/**
+ * Free HTTP request
+ *
+ * @v refcnt		Reference counter
+ */
+static void http_free ( struct refcnt *refcnt ) {
+	struct http_request *http =
+		container_of ( refcnt, struct http_request, refcnt );
+
+	uri_put ( http->uri );
+	empty_line_buffer ( &http->linebuf );
+	free ( http );
+};
+
+/**
+ * Close HTTP request
+ *
+ * @v http		HTTP request
+ * @v rc		Return status code
+ */
+static void http_close ( struct http_request *http, int rc ) {
+
+	/* Prevent further processing of any current packet */
+	http->rx_state = HTTP_RX_DEAD;
+
+	/* If we had a Content-Length, and the received content length
+	 * isn't correct, flag an error
+	 */
+	if ( http->remaining != 0 ) {
+		DBGC ( http, "HTTP %p incorrect length %zd, should be %zd\n",
+		       http, http->rx_len, ( http->rx_len + http->remaining ) );
+		if ( rc == 0 )
+			rc = -EIO;
+	}
+
+	/* Remove process */
+	process_del ( &http->process );
+
+	/* Close all data transfer interfaces */
+	intf_shutdown ( &http->socket, rc );
+	intf_shutdown ( &http->partial, rc );
+	intf_shutdown ( &http->xfer, rc );
+}
+
+/**
+ * Mark HTTP request as completed successfully
+ *
+ * @v http		HTTP request
+ */
+static void http_done ( struct http_request *http ) {
+
+	/* If we had a Content-Length, and the received content length
+	 * isn't correct, force an error
+	 */
+	if ( http->remaining != 0 ) {
+		http_close ( http, -EIO );
+		return;
+	}
+
+	/* Enter idle state */
+	http->rx_state = HTTP_RX_IDLE;
+	http->rx_len = 0;
+	assert ( http->remaining == 0 );
+	assert ( http->chunked == 0 );
+	assert ( http->chunk_remaining == 0 );
+
+	/* Close partial transfer interface */
+	intf_restart ( &http->partial, 0 );
+
+	/* Close everything unless we are keeping the connection alive */
+	if ( ! ( http->flags & HTTP_KEEPALIVE ) )
+		http_close ( http, 0 );
+}
+
+/**
+ * Convert HTTP response code to return status code
+ *
+ * @v response		HTTP response code
+ * @ret rc		Return status code
+ */
+static int http_response_to_rc ( unsigned int response ) {
+	switch ( response ) {
+	case 200:
+	case 206:
+	case 301:
+	case 302:
+		return 0;
+	case 404:
+		return -ENOENT;
+	case 403:
+		return -EPERM;
+	case 401:
+		return -EACCES;
+	default:
+		return -EIO;
+	}
+}
+
+/**
+ * Handle HTTP response
+ *
+ * @v http		HTTP request
+ * @v response		HTTP response
+ * @ret rc		Return status code
+ */
+static int http_rx_response ( struct http_request *http, char *response ) {
+	char *spc;
+	unsigned int code;
+	int rc;
+
+	DBGC ( http, "HTTP %p response \"%s\"\n", http, response );
+
+	/* Check response starts with "HTTP/" */
+	if ( strncmp ( response, "HTTP/", 5 ) != 0 )
+		return -EIO;
+
+	/* Locate and check response code */
+	spc = strchr ( response, ' ' );
+	if ( ! spc )
+		return -EIO;
+	code = strtoul ( spc, NULL, 10 );
+	if ( ( rc = http_response_to_rc ( code ) ) != 0 )
+		return rc;
+
+	/* Move to received headers */
+	http->rx_state = HTTP_RX_HEADER;
+	return 0;
+}
+
+/**
+ * Handle HTTP Location header
+ *
+ * @v http		HTTP request
+ * @v value		HTTP header value
+ * @ret rc		Return status code
+ */
+static int http_rx_location ( struct http_request *http, const char *value ) {
+	int rc;
+
+	/* Redirect to new location */
+	DBGC ( http, "HTTP %p redirecting to %s\n", http, value );
+	if ( ( rc = xfer_redirect ( &http->xfer, LOCATION_URI_STRING,
+				    value ) ) != 0 ) {
+		DBGC ( http, "HTTP %p could not redirect: %s\n",
+		       http, strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Handle HTTP Content-Length header
+ *
+ * @v http		HTTP request
+ * @v value		HTTP header value
+ * @ret rc		Return status code
+ */
+static int http_rx_content_length ( struct http_request *http,
+				    const char *value ) {
+	struct block_device_capacity capacity;
+	size_t content_len;
+	char *endp;
+
+	/* Parse content length */
+	content_len = strtoul ( value, &endp, 10 );
+	if ( *endp != '\0' ) {
+		DBGC ( http, "HTTP %p invalid Content-Length \"%s\"\n",
+		       http, value );
+		return -EIO;
+	}
+
+	/* If we already have an expected content length, and this
+	 * isn't it, then complain
+	 */
+	if ( http->remaining && ( http->remaining != content_len ) ) {
+		DBGC ( http, "HTTP %p incorrect Content-Length %zd (expected "
+		       "%zd)\n", http, content_len, http->remaining );
+		return -EIO;
+	}
+	if ( ! ( http->flags & HTTP_HEAD_ONLY ) )
+		http->remaining = content_len;
+
+	/* Use seek() to notify recipient of filesize */
+	xfer_seek ( &http->xfer, http->remaining );
+	xfer_seek ( &http->xfer, 0 );
+
+	/* Report block device capacity if applicable */
+	if ( http->flags & HTTP_HEAD_ONLY ) {
+		capacity.blocks = ( content_len / HTTP_BLKSIZE );
+		capacity.blksize = HTTP_BLKSIZE;
+		capacity.max_count = -1U;
+		block_capacity ( &http->partial, &capacity );
+	}
+	return 0;
+}
+
+/**
+ * Handle HTTP Transfer-Encoding header
+ *
+ * @v http		HTTP request
+ * @v value		HTTP header value
+ * @ret rc		Return status code
+ */
+static int http_rx_transfer_encoding ( struct http_request *http,
+				       const char *value ) {
+
+	if ( strcmp ( value, "chunked" ) == 0 ) {
+		/* Mark connection as using chunked transfer encoding */
+		http->chunked = 1;
+	}
+
+	return 0;
+}
+
+/** An HTTP header handler */
+struct http_header_handler {
+	/** Name (e.g. "Content-Length") */
+	const char *header;
+	/** Handle received header
+	 *
+	 * @v http	HTTP request
+	 * @v value	HTTP header value
+	 * @ret rc	Return status code
+	 *
+	 * If an error is returned, the download will be aborted.
+	 */
+	int ( * rx ) ( struct http_request *http, const char *value );
+};
+
+/** List of HTTP header handlers */
+static struct http_header_handler http_header_handlers[] = {
+	{
+		.header = "Location",
+		.rx = http_rx_location,
+	},
+	{
+		.header = "Content-Length",
+		.rx = http_rx_content_length,
+	},
+	{
+		.header = "Transfer-Encoding",
+		.rx = http_rx_transfer_encoding,
+	},
+	{ NULL, NULL }
+};
+
+/**
+ * Handle HTTP header
+ *
+ * @v http		HTTP request
+ * @v header		HTTP header
+ * @ret rc		Return status code
+ */
+static int http_rx_header ( struct http_request *http, char *header ) {
+	struct http_header_handler *handler;
+	char *separator;
+	char *value;
+	int rc;
+
+	/* An empty header line marks the end of this phase */
+	if ( ! header[0] ) {
+		empty_line_buffer ( &http->linebuf );
+		if ( ( http->rx_state == HTTP_RX_HEADER ) &&
+		     ( ! ( http->flags & HTTP_HEAD_ONLY ) ) ) {
+			DBGC ( http, "HTTP %p start of data\n", http );
+			http->rx_state = ( http->chunked ?
+					   HTTP_RX_CHUNK_LEN : HTTP_RX_DATA );
+			return 0;
+		} else {
+			DBGC ( http, "HTTP %p end of trailer\n", http );
+			http_done ( http );
+			return 0;
+		}
+	}
+
+	DBGC ( http, "HTTP %p header \"%s\"\n", http, header );
+
+	/* Split header at the ": " */
+	separator = strstr ( header, ": " );
+	if ( ! separator ) {
+		DBGC ( http, "HTTP %p malformed header\n", http );
+		return -EIO;
+	}
+	*separator = '\0';
+	value = ( separator + 2 );
+
+	/* Hand off to header handler, if one exists */
+	for ( handler = http_header_handlers ; handler->header ; handler++ ) {
+		if ( strcasecmp ( header, handler->header ) == 0 ) {
+			if ( ( rc = handler->rx ( http, value ) ) != 0 )
+				return rc;
+			break;
+		}
+	}
+	return 0;
+}
+
+/**
+ * Handle HTTP chunk length
+ *
+ * @v http		HTTP request
+ * @v length		HTTP chunk length
+ * @ret rc		Return status code
+ */
+static int http_rx_chunk_len ( struct http_request *http, char *length ) {
+	char *endp;
+
+	/* Skip blank lines between chunks */
+	if ( length[0] == '\0' )
+		return 0;
+
+	/* Parse chunk length */
+	http->chunk_remaining = strtoul ( length, &endp, 16 );
+	if ( *endp != '\0' ) {
+		DBGC ( http, "HTTP %p invalid chunk length \"%s\"\n",
+		       http, length );
+		return -EIO;
+	}
+
+	/* Terminate chunked encoding if applicable */
+	if ( http->chunk_remaining == 0 ) {
+		DBGC ( http, "HTTP %p end of chunks\n", http );
+		http->chunked = 0;
+		http->rx_state = HTTP_RX_TRAILER;
+		return 0;
+	}
+
+	/* Use seek() to notify recipient of new filesize */
+	DBGC ( http, "HTTP %p start of chunk of length %zd\n",
+	       http, http->chunk_remaining );
+	xfer_seek ( &http->xfer, ( http->rx_len + http->chunk_remaining ) );
+	xfer_seek ( &http->xfer, http->rx_len );
+
+	/* Start receiving data */
+	http->rx_state = HTTP_RX_DATA;
+
+	return 0;
+}
+
+/** An HTTP line-based data handler */
+struct http_line_handler {
+	/** Handle line
+	 *
+	 * @v http	HTTP request
+	 * @v line	Line to handle
+	 * @ret rc	Return status code
+	 */
+	int ( * rx ) ( struct http_request *http, char *line );
+};
+
+/** List of HTTP line-based data handlers */
+static struct http_line_handler http_line_handlers[] = {
+	[HTTP_RX_RESPONSE]	= { .rx = http_rx_response },
+	[HTTP_RX_HEADER]	= { .rx = http_rx_header },
+	[HTTP_RX_CHUNK_LEN]	= { .rx = http_rx_chunk_len },
+	[HTTP_RX_TRAILER]	= { .rx = http_rx_header },
+};
+
+/**
+ * Handle new data arriving via HTTP connection
+ *
+ * @v http		HTTP request
+ * @v iobuf		I/O buffer
+ * @v meta		Data transfer metadata
+ * @ret rc		Return status code
+ */
+static int http_socket_deliver ( struct http_request *http,
+				 struct io_buffer *iobuf,
+				 struct xfer_metadata *meta __unused ) {
+	struct http_line_handler *lh;
+	char *line;
+	size_t data_len;
+	ssize_t line_len;
+	int rc = 0;
+
+	while ( iobuf && iob_len ( iobuf ) ) {
+
+		switch ( http->rx_state ) {
+		case HTTP_RX_IDLE:
+			/* Receiving any data in this state is an error */
+			DBGC ( http, "HTTP %p received %zd bytes while %s\n",
+			       http, iob_len ( iobuf ),
+			       ( ( http->rx_state == HTTP_RX_IDLE ) ?
+				 "idle" : "dead" ) );
+			rc = -EPROTO;
+			goto done;
+		case HTTP_RX_DEAD:
+			/* Do no further processing */
+			goto done;
+		case HTTP_RX_DATA:
+			/* Pass received data to caller */
+			data_len = iob_len ( iobuf );
+			if ( http->chunk_remaining &&
+			     ( http->chunk_remaining < data_len ) ) {
+				data_len = http->chunk_remaining;
+			}
+			if ( http->remaining &&
+			     ( http->remaining < data_len ) ) {
+				data_len = http->remaining;
+			}
+			if ( http->rx_buffer != UNULL ) {
+				/* Copy to partial transfer buffer */
+				copy_to_user ( http->rx_buffer, http->rx_len,
+					       iobuf->data, data_len );
+				iob_pull ( iobuf, data_len );
+			} else if ( data_len < iob_len ( iobuf ) ) {
+				/* Deliver partial buffer as raw data */
+				rc = xfer_deliver_raw ( &http->xfer,
+							iobuf->data, data_len );
+				iob_pull ( iobuf, data_len );
+				if ( rc != 0 )
+					goto done;
+			} else {
+				/* Deliver whole I/O buffer */
+				if ( ( rc = xfer_deliver_iob ( &http->xfer,
+						 iob_disown ( iobuf ) ) ) != 0 )
+					goto done;
+			}
+			http->rx_len += data_len;
+			if ( http->chunk_remaining ) {
+				http->chunk_remaining -= data_len;
+				if ( http->chunk_remaining == 0 )
+					http->rx_state = HTTP_RX_CHUNK_LEN;
+			}
+			if ( http->remaining ) {
+				http->remaining -= data_len;
+				if ( ( http->remaining == 0 ) &&
+				     ( http->rx_state == HTTP_RX_DATA ) ) {
+					http_done ( http );
+				}
+			}
+			break;
+		case HTTP_RX_RESPONSE:
+		case HTTP_RX_HEADER:
+		case HTTP_RX_CHUNK_LEN:
+		case HTTP_RX_TRAILER:
+			/* In the other phases, buffer and process a
+			 * line at a time
+			 */
+			line_len = line_buffer ( &http->linebuf, iobuf->data,
+						 iob_len ( iobuf ) );
+			if ( line_len < 0 ) {
+				rc = line_len;
+				DBGC ( http, "HTTP %p could not buffer line: "
+				       "%s\n", http, strerror ( rc ) );
+				goto done;
+			}
+			iob_pull ( iobuf, line_len );
+			line = buffered_line ( &http->linebuf );
+			if ( line ) {
+				lh = &http_line_handlers[http->rx_state];
+				if ( ( rc = lh->rx ( http, line ) ) != 0 )
+					goto done;
+			}
+			break;
+		default:
+			assert ( 0 );
+			break;
+		}
+	}
+
+ done:
+	if ( rc )
+		http_close ( http, rc );
+	free_iob ( iobuf );
+	return rc;
+}
+
+/**
+ * Check HTTP socket flow control window
+ *
+ * @v http		HTTP request
+ * @ret len		Length of window
+ */
+static size_t http_socket_window ( struct http_request *http __unused ) {
+
+	/* Window is always open.  This is to prevent TCP from
+	 * stalling if our parent window is not currently open.
+	 */
+	return ( ~( ( size_t ) 0 ) );
+}
+
+/**
+ * HTTP process
+ *
+ * @v http		HTTP request
+ */
+static void http_step ( struct http_request *http ) {
+	const char *host = http->uri->host;
+	const char *user = http->uri->user;
+	const char *password =
+		( http->uri->password ? http->uri->password : "" );
+	size_t user_pw_len = ( user ? ( strlen ( user ) + 1 /* ":" */ +
+					strlen ( password ) ) : 0 );
+	size_t user_pw_base64_len = base64_encoded_len ( user_pw_len );
+	uint8_t user_pw[ user_pw_len + 1 /* NUL */ ];
+	char user_pw_base64[ user_pw_base64_len + 1 /* NUL */ ];
+	int rc;
+	int request_len = unparse_uri ( NULL, 0, http->uri,
+					URI_PATH_BIT | URI_QUERY_BIT );
+	char request[ request_len + 1 /* NUL */ ];
+	char range[48]; /* Enough for two 64-bit integers in decimal */
+	int partial;
+
+	/* Do nothing if we have already transmitted the request */
+	if ( ! ( http->flags & HTTP_TX_PENDING ) )
+		return;
+
+	/* Do nothing until socket is ready */
+	if ( ! xfer_window ( &http->socket ) )
+		return;
+
+	/* Construct path?query request */
+	unparse_uri ( request, sizeof ( request ), http->uri,
+		      URI_PATH_BIT | URI_QUERY_BIT );
+
+	/* Construct authorisation, if applicable */
+	if ( user ) {
+		/* Make "user:password" string from decoded fields */
+		snprintf ( ( ( char * ) user_pw ), sizeof ( user_pw ),
+			   "%s:%s", user, password );
+
+		/* Base64-encode the "user:password" string */
+		base64_encode ( user_pw, user_pw_len, user_pw_base64 );
+	}
+
+	/* Force a HEAD request if we have nowhere to send any received data */
+	if ( ( xfer_window ( &http->xfer ) == 0 ) &&
+	     ( http->rx_buffer == UNULL ) ) {
+		http->flags |= ( HTTP_HEAD_ONLY | HTTP_KEEPALIVE );
+	}
+
+	/* Determine type of request */
+	partial = ( http->partial_len != 0 );
+	snprintf ( range, sizeof ( range ), "%zd-%zd", http->partial_start,
+		   ( http->partial_start + http->partial_len - 1 ) );
+
+	/* Mark request as transmitted */
+	http->flags &= ~HTTP_TX_PENDING;
+
+	/* Send GET request */
+	if ( ( rc = xfer_printf ( &http->socket,
+				  "%s %s%s HTTP/1.1\r\n"
+				  "User-Agent: iPXE/" VERSION "\r\n"
+				  "Host: %s%s%s\r\n"
+				  "%s%s%s%s%s%s%s"
+				  "\r\n",
+				  ( ( http->flags & HTTP_HEAD_ONLY ) ?
+				    "HEAD" : "GET" ),
+				  ( http->uri->path ? "" : "/" ),
+				  request, host,
+				  ( http->uri->port ?
+				    ":" : "" ),
+				  ( http->uri->port ?
+				    http->uri->port : "" ),
+				  ( ( http->flags & HTTP_KEEPALIVE ) ?
+				    "Connection: Keep-Alive\r\n" : "" ),
+				  ( partial ? "Range: bytes=" : "" ),
+				  ( partial ? range : "" ),
+				  ( partial ? "\r\n" : "" ),
+				  ( user ?
+				    "Authorization: Basic " : "" ),
+				  ( user ? user_pw_base64 : "" ),
+				  ( user ? "\r\n" : "" ) ) ) != 0 ) {
+		http_close ( http, rc );
+	}
+}
+
+/**
+ * Check HTTP data transfer flow control window
+ *
+ * @v http		HTTP request
+ * @ret len		Length of window
+ */
+static size_t http_xfer_window ( struct http_request *http ) {
+
+	/* New block commands may be issued only when we are idle */
+	return ( ( http->rx_state == HTTP_RX_IDLE ) ? 1 : 0 );
+}
+
+/**
+ * Initiate HTTP partial read
+ *
+ * @v http		HTTP request
+ * @v partial		Partial transfer interface
+ * @v offset		Starting offset
+ * @v buffer		Data buffer
+ * @v len		Length
+ * @ret rc		Return status code
+ */
+static int http_partial_read ( struct http_request *http,
+			       struct interface *partial,
+			       size_t offset, userptr_t buffer, size_t len ) {
+
+	/* Sanity check */
+	if ( http_xfer_window ( http ) == 0 )
+		return -EBUSY;
+
+	/* Initialise partial transfer parameters */
+	http->rx_buffer = buffer;
+	http->partial_start = offset;
+	http->partial_len = len;
+	http->remaining = len;
+
+	/* Schedule request */
+	http->rx_state = HTTP_RX_RESPONSE;
+	http->flags = ( HTTP_TX_PENDING | HTTP_KEEPALIVE );
+	if ( ! len )
+		http->flags |= HTTP_HEAD_ONLY;
+	process_add ( &http->process );
+
+	/* Attach to parent interface and return */
+	intf_plug_plug ( &http->partial, partial );
+
+	return 0;
+}
+
+/**
+ * Issue HTTP block device read
+ *
+ * @v http		HTTP request
+ * @v block		Block data interface
+ * @v lba		Starting logical block address
+ * @v count		Number of blocks to transfer
+ * @v buffer		Data buffer
+ * @v len		Length of data buffer
+ * @ret rc		Return status code
+ */
+static int http_block_read ( struct http_request *http,
+			     struct interface *block,
+			     uint64_t lba, unsigned int count,
+			     userptr_t buffer, size_t len __unused ) {
+
+	return http_partial_read ( http, block, ( lba * HTTP_BLKSIZE ),
+				   buffer, ( count * HTTP_BLKSIZE ) );
+}
+
+/**
+ * Read HTTP block device capacity
+ *
+ * @v http		HTTP request
+ * @v block		Block data interface
+ * @ret rc		Return status code
+ */
+static int http_block_read_capacity ( struct http_request *http,
+				      struct interface *block ) {
+
+	return http_partial_read ( http, block, 0, 0, 0 );
+}
+
+/**
+ * Describe HTTP device in an ACPI table
+ *
+ * @v http		HTTP request
+ * @v acpi		ACPI table
+ * @v len		Length of ACPI table
+ * @ret rc		Return status code
+ */
+static int http_acpi_describe ( struct http_request *http,
+				struct acpi_description_header *acpi,
+				size_t len ) {
+
+	DBGC ( http, "HTTP %p cannot yet describe device in an ACPI table\n",
+	       http );
+	( void ) acpi;
+	( void ) len;
+	return 0;
+}
+
+/** HTTP socket interface operations */
+static struct interface_operation http_socket_operations[] = {
+	INTF_OP ( xfer_window, struct http_request *, http_socket_window ),
+	INTF_OP ( xfer_deliver, struct http_request *, http_socket_deliver ),
+	INTF_OP ( xfer_window_changed, struct http_request *, http_step ),
+	INTF_OP ( intf_close, struct http_request *, http_close ),
+};
+
+/** HTTP socket interface descriptor */
+static struct interface_descriptor http_socket_desc =
+	INTF_DESC_PASSTHRU ( struct http_request, socket,
+			     http_socket_operations, xfer );
+
+/** HTTP partial transfer interface operations */
+static struct interface_operation http_partial_operations[] = {
+	INTF_OP ( intf_close, struct http_request *, http_close ),
+};
+
+/** HTTP partial transfer interface descriptor */
+static struct interface_descriptor http_partial_desc =
+	INTF_DESC ( struct http_request, partial, http_partial_operations );
+
+/** HTTP data transfer interface operations */
+static struct interface_operation http_xfer_operations[] = {
+	INTF_OP ( xfer_window, struct http_request *, http_xfer_window ),
+	INTF_OP ( block_read, struct http_request *, http_block_read ),
+	INTF_OP ( block_read_capacity, struct http_request *,
+		  http_block_read_capacity ),
+	INTF_OP ( intf_close, struct http_request *, http_close ),
+	INTF_OP ( acpi_describe, struct http_request *, http_acpi_describe ),
+};
+
+/** HTTP data transfer interface descriptor */
+static struct interface_descriptor http_xfer_desc =
+	INTF_DESC_PASSTHRU ( struct http_request, xfer,
+			     http_xfer_operations, socket );
+
+/** HTTP process descriptor */
+static struct process_descriptor http_process_desc =
+	PROC_DESC_ONCE ( struct http_request, process, http_step );
+
+/**
+ * Initiate an HTTP connection, with optional filter
+ *
+ * @v xfer		Data transfer interface
+ * @v uri		Uniform Resource Identifier
+ * @v default_port	Default port number
+ * @v filter		Filter to apply to socket, or NULL
+ * @ret rc		Return status code
+ */
+int http_open_filter ( struct interface *xfer, struct uri *uri,
+		       unsigned int default_port,
+		       int ( * filter ) ( struct interface *xfer,
+					  struct interface **next ) ) {
+	struct http_request *http;
+	struct sockaddr_tcpip server;
+	struct interface *socket;
+	int rc;
+
+	/* Sanity checks */
+	if ( ! uri->host )
+		return -EINVAL;
+
+	/* Allocate and populate HTTP structure */
+	http = zalloc ( sizeof ( *http ) );
+	if ( ! http )
+		return -ENOMEM;
+	ref_init ( &http->refcnt, http_free );
+	intf_init ( &http->xfer, &http_xfer_desc, &http->refcnt );
+	intf_init ( &http->partial, &http_partial_desc, &http->refcnt );
+	http->uri = uri_get ( uri );
+	intf_init ( &http->socket, &http_socket_desc, &http->refcnt );
+	process_init ( &http->process, &http_process_desc, &http->refcnt );
+	http->flags = HTTP_TX_PENDING;
+
+	/* Open socket */
+	memset ( &server, 0, sizeof ( server ) );
+	server.st_port = htons ( uri_port ( http->uri, default_port ) );
+	socket = &http->socket;
+	if ( filter ) {
+		if ( ( rc = filter ( socket, &socket ) ) != 0 )
+			goto err;
+	}
+	if ( ( rc = xfer_open_named_socket ( socket, SOCK_STREAM,
+					     ( struct sockaddr * ) &server,
+					     uri->host, NULL ) ) != 0 )
+		goto err;
+
+	/* Attach to parent interface, mortalise self, and return */
+	intf_plug_plug ( &http->xfer, xfer );
+	ref_put ( &http->refcnt );
+	return 0;
+
+ err:
+	DBGC ( http, "HTTP %p could not create request: %s\n",
+	       http, strerror ( rc ) );
+	http_close ( http, rc );
+	ref_put ( &http->refcnt );
+	return rc;
+}