Remove unused push promise support (#642)

Remove the HTTP/2 and HTTP/3 push promise implementation while keeping the 
public APIs in place as disabled stubs.  Server push is no longer used,
so this drops the associated state, frame generation, parsing callbacks,
and stream bookkeeping.  Update tests and documentation to cover the
disabled behavior and the remaining HTTP/3 framing paths.

Author: dtikhonov

include/lsquic.h

@@ -333,8 +333,8 @@ typedef struct ssl_ctx_st * (*lsquic_lookup_cert_f)(
 
 /** Do not use NSTP by default */
 #define LSQUIC_DF_SUPPORT_NSTP     0
-/** TODO: IETF QUIC clients do not support push */
-#define LSQUIC_DF_SUPPORT_PUSH         1
+/** Server push is not supported */
+#define LSQUIC_DF_SUPPORT_PUSH         0
 #define LSQUIC_DF_SUPPORT_TCID0    1
 /** By default, LSQUIC ignores Public Reset packets. */
 #define LSQUIC_DF_HONOR_PRST       0
@@ -606,16 +606,8 @@ struct lsquic_engine_settings {
     int             es_support_srej;
 
     /**
-     * Setting this value to 0 means that
-     *
-     * For client:
-     *  a) we send a SETTINGS frame to indicate that we do not support server
-     *     push; and
-     *  b) All incoming pushed streams get reset immediately.
-     * (For maximum effect, set es_max_streams_in to 0.)
-     *
-     * For server:
-     *  lsquic_conn_push_stream() will return -1.
+     * Server push is not supported.  lsquic_conn_is_push_enabled() returns
+     * false and lsquic_conn_push_stream() returns 1.
      */
     int             es_support_push;
 

src/liblsquic/lsquic_conn_public.h

@@ -44,7 +44,6 @@ struct lsquic_conn_public {
             struct qpack_enc_hdl *qeh;
             struct qpack_dec_hdl *qdh;
             struct hcso_writer   *hcso;
-            struct lsquic_hash   *promises;
         }                       ietf;
     }                               u;
     enum {

src/liblsquic/lsquic_ev_log.c

@@ -522,25 +522,6 @@ lsquic_ev_log_generated_http_headers (const lsquic_cid_t *cid,
 }
 
 
-void
-lsquic_ev_log_generated_http_push_promise (const lsquic_cid_t *cid,
-            lsquic_stream_id_t stream_id, lsquic_stream_id_t promised_stream_id, 
-            const struct lsquic_http_headers *headers)
-{
-    int i;
-
-    LCID("generated HTTP PUSH_PROMISE for stream %"PRIu64"; promised stream %"
-        PRIu64, stream_id, promised_stream_id);
-
-    for (i = 0; i < headers->count; ++i)
-        if (headers->headers[i].buf)
-            LCID("  %.*s: %.*s",
-                (int)    headers->headers[i].name_len,
-                lsxpack_header_get_name(&headers->headers[i]),
-                (int)    headers->headers[i].val_len,
-                lsxpack_header_get_value(&headers->headers[i]));
-}
-
 void
 lsquic_ev_log_create_connection (const lsquic_cid_t *cid,
                                     const struct sockaddr *local_sa,

src/liblsquic/lsquic_ev_log.h

@@ -278,16 +278,6 @@ lsquic_ev_log_generated_http_headers (const lsquic_cid_t *, lsquic_stream_id_t,
         lsquic_ev_log_generated_http_headers(__VA_ARGS__);                  \
 } while (0)
 
-void
-lsquic_ev_log_generated_http_push_promise (const lsquic_cid_t *,
-        lsquic_stream_id_t stream_id, lsquic_stream_id_t promised_stream_id,
-        const struct lsquic_http_headers *headers);
-
-#define EV_LOG_GENERATED_HTTP_PUSH_PROMISE(...) do {                        \
-    if (LSQ_LOG_ENABLED_EXT(LSQ_LOG_DEBUG, LSQLM_EVENT))                    \
-        lsquic_ev_log_generated_http_push_promise(__VA_ARGS__);             \
-} while (0)
-
 void
 lsquic_ev_log_create_connection (const lsquic_cid_t *, const struct sockaddr *,
                                                     const struct sockaddr *);

src/liblsquic/lsquic_frame_common.h

@@ -66,12 +66,6 @@ struct http_prio_frame          /* RFC 7540, Section 6.3 */
 };
 
 
-struct http_push_promise_frame  /* RFC 7540, Section 6.6 */
-{
-    unsigned char   hppf_promised_id[4];    /* High bit is reserved */
-};
-
-
 struct lsquic_http2_setting
 {
     uint16_t id;

src/liblsquic/lsquic_frame_reader.c

@@ -31,26 +31,23 @@
 #include "lsquic_logger.h"
 
 
-/* headers_state is used by HEADERS, PUSH_PROMISE, and CONTINUATION frames */
+/* headers_state is used by HEADERS and CONTINUATION frames */
 struct headers_state
 {
     enum http_frame_type
                     frame_type;
     unsigned        nread;  /* Not counting pesw, only payload and padding */
 
     /* Values parsed out from pesw buffer: */
-    uint32_t        oth_stream_id;  /* For HEADERS: ID of stream we depend on;
-                                     * for PUSH_PROMISE: promised stream ID.
-                                     */
+    uint32_t        oth_stream_id;  /* For HEADERS: ID of stream we depend on */
     unsigned short  weight;         /* HEADERS only */
     signed char     exclusive;      /* HEADERS only */
     unsigned char   pad_length;
 
     unsigned char   pseh;
 
     /* PESW: Pad length, Exclusive, Stream Dependency, Weight.  This is at
-     * most six bytes for HEADERS frame (RFC 7540, page 33) and five bytes
-     * for PUSH_PROMISE frame (Ibid, p. 40).
+     * most six bytes for HEADERS frame (RFC 7540, page 33).
      */
     unsigned char   pesw_size;
     unsigned char   pesw_nread;
@@ -88,7 +85,6 @@ struct reader_state
     enum {
         READER_SKIP,
         READER_HEADERS,
-        READER_PUSH_PROMISE,
         READER_CONTIN,
         READER_SETTINGS,
         READER_PRIORITY,
@@ -115,8 +111,8 @@ struct lsquic_frame_reader
     const struct lsquic_hset_if     *fr_hsi_if;
     void                            *fr_hsi_ctx;
     struct http1x_ctor_ctx           fr_h1x_ctor_ctx;
-    /* The the header block is shared between HEADERS, PUSH_PROMISE, and
-     * CONTINUATION frames.  It gets added to as block fragments come in.
+    /* The header block is shared between HEADERS and CONTINUATION frames.
+     * It gets added to as block fragments come in.
      */
     unsigned char                   *fr_header_block;
 #if LSQUIC_CONN_STATS
@@ -258,7 +254,6 @@ prepare_for_payload (struct lsquic_frame_reader *fr)
     if (fr->fr_state.header.hfh_type != HTTP_FRAME_CONTINUATION &&
         (fr->fr_flags & FRF_HAVE_PREV) &&
         (fr->fr_prev_frame_type == HTTP_FRAME_HEADERS      ||
-         fr->fr_prev_frame_type == HTTP_FRAME_PUSH_PROMISE ||
          fr->fr_prev_frame_type == HTTP_FRAME_CONTINUATION    ) &&
         0 == (fr->fr_prev_hfh_flags & HFHF_END_HEADERS))
     {
@@ -307,47 +302,17 @@ prepare_for_payload (struct lsquic_frame_reader *fr)
         fr->fr_state.reader_type = READER_HEADERS;
         break;
     case HTTP_FRAME_PUSH_PROMISE:
-        if (fr->fr_flags & FRF_SERVER)
-        {
-            LSQ_INFO("clients should not push promised");
-            fr->fr_callbacks->frc_on_error(fr->fr_cb_ctx, stream_id,
+        LSQ_INFO("received PUSH_PROMISE but push promises are not supported");
+        fr->fr_callbacks->frc_on_error(fr->fr_cb_ctx, stream_id,
                                                     FR_ERR_UNEXPECTED_PUSH);
-            return -1;
-        }
-        if (fr->fr_max_headers_sz &&
-            fr->fr_state.payload_length > fr->fr_max_headers_sz)
-            goto headers_too_large;
-        fr->fr_state.by_type.headers_state.frame_type = HTTP_FRAME_PUSH_PROMISE;
-        fr->fr_state.by_type.headers_state.nread = 0;
-        fr->fr_state.by_type.headers_state.pesw_nread = 0;
-        fr->fr_state.by_type.headers_state.pseh = 0;
-        if (fr->fr_state.header.hfh_flags & HFHF_PADDED)
-            fr->fr_state.by_type.headers_state.pesw_size = 5;
-        else
-        {
-            fr->fr_state.by_type.headers_state.pad_length = 0;
-            fr->fr_state.by_type.headers_state.pesw_size = 4;
-        }
-        LSQ_DEBUG("pesw size: %u; payload length: %u; flags: 0x%X",
-            fr->fr_state.by_type.headers_state.pesw_size,
-            fr->fr_state.payload_length, fr->fr_state.header.hfh_flags);
-        if (fr->fr_state.by_type.headers_state.pesw_size >
-                                        fr->fr_state.payload_length)
-        {
-            LSQ_INFO("Invalid headers frame: payload length too small");
-            errno = EBADMSG;
-            return -1;
-        }
-        fr->fr_state.reader_type = READER_PUSH_PROMISE;
-        break;
+        return -1;
     case HTTP_FRAME_CONTINUATION:
         if (0 == (fr->fr_flags & FRF_HAVE_PREV))
         {
             LSQ_INFO("Framing error: unexpected CONTINUATION");
             return -1;
         }
         if (!(fr->fr_prev_frame_type == HTTP_FRAME_HEADERS      ||
-              fr->fr_prev_frame_type == HTTP_FRAME_PUSH_PROMISE ||
               fr->fr_prev_frame_type == HTTP_FRAME_CONTINUATION))
         {
             LSQ_INFO("Framing error: unexpected CONTINUATION");
@@ -591,7 +556,7 @@ decode_and_pass_payload (struct lsquic_frame_reader *fr)
         }
     }
     hset = fr->fr_hsi_if->hsi_create_header_set(fr->fr_hsi_ctx, target_stream,
-                            READER_PUSH_PROMISE == fr->fr_state.reader_type);
+                            0);
     if (!hset)
     {
         err = FR_ERR_OTHER_ERROR;
@@ -658,31 +623,17 @@ decode_and_pass_payload (struct lsquic_frame_reader *fr)
                                                 sizeof(stream_id32));
     uh->uh_stream_id     = ntohl(stream_id32);
     uh->uh_oth_stream_id = hs->oth_stream_id;
-    if (HTTP_FRAME_HEADERS == fr->fr_state.by_type.headers_state.frame_type)
-    {
-        uh->uh_weight    = hs->weight;
-        uh->uh_exclusive = hs->exclusive;
-        uh->uh_flags     = 0;
-    }
-    else
-    {
-        assert(HTTP_FRAME_PUSH_PROMISE ==
-                                fr->fr_state.by_type.headers_state.frame_type);
-        uh->uh_weight    = 0;   /* Zero unused value */
-        uh->uh_exclusive = 0;   /* Zero unused value */
-        uh->uh_flags     = UH_PP;
-    }
+    uh->uh_weight    = hs->weight;
+    uh->uh_exclusive = hs->exclusive;
+    uh->uh_flags     = 0;
     if (fr->fr_state.header.hfh_flags & HFHF_END_STREAM)
         uh->uh_flags    |= UH_FIN;
     if (fr->fr_hsi_if == lsquic_http1x_if)
         uh->uh_flags    |= UH_H1H;
     uh->uh_hset = hset;
 
     EV_LOG_HTTP_HEADERS_IN(LSQUIC_LOG_CONN_ID, fr->fr_flags & FRF_SERVER, uh);
-    if (HTTP_FRAME_HEADERS == fr->fr_state.by_type.headers_state.frame_type)
-        fr->fr_callbacks->frc_on_headers(fr->fr_cb_ctx, uh);
-    else
-        fr->fr_callbacks->frc_on_push_promise(fr->fr_cb_ctx, uh);
+    fr->fr_callbacks->frc_on_headers(fr->fr_cb_ctx, uh);
 #if LSQUIC_CONN_STATS
     fr->fr_conn_stats->in.headers_comp += fr->fr_header_block_sz;
 #endif
@@ -802,48 +753,6 @@ read_headers (struct lsquic_frame_reader *fr)
 }
 
 
-static int
-read_push_promise_pesw (struct lsquic_frame_reader *fr)
-{
-    struct headers_state *hs = &fr->fr_state.by_type.headers_state;
-    ssize_t nr = fr->fr_read(fr->fr_stream, hs->pesw + hs->pesw_nread,
-                                            hs->pesw_size - hs->pesw_nread);
-    if (nr <= 0)
-        RETURN_ERROR(nr);
-    hs->pesw_nread += nr;
-    if (hs->pesw_nread == hs->pesw_size)
-    {
-        unsigned char *p = hs->pesw;
-        if (fr->fr_state.header.hfh_flags & HFHF_PADDED)
-            hs->pad_length = *p++;
-        p[0] &= ~0x80;  /* Clear reserved bit.  Note: modifying pesw buffer. */
-        memcpy(&hs->oth_stream_id, p, sizeof(hs->oth_stream_id));
-        hs->oth_stream_id = ntohl(hs->oth_stream_id);
-        p += 4;
-        assert(p - hs->pesw == hs->pesw_size);
-        if (hs->pesw_size + hs->pad_length > fr->fr_state.payload_length)
-        {
-            LSQ_INFO("Invalid PUSH_PROMISE frame: pesw length and padding length "
-                    "are larger than the payload length");
-            errno = EBADMSG;
-            return -1;
-        }
-    }
-    return 0;
-}
-
-
-static int
-read_push_promise (struct lsquic_frame_reader *fr)
-{
-    struct headers_state *hs = &fr->fr_state.by_type.headers_state;
-    if (hs->pesw_nread < hs->pesw_size)
-        return read_push_promise_pesw(fr);
-    else
-        return read_headers_block_fragment_and_padding(fr);
-}
-
-
 static int
 read_contin (struct lsquic_frame_reader *fr)
 {
@@ -954,8 +863,6 @@ read_payload (struct lsquic_frame_reader *fr)
     {
     case READER_HEADERS:
         return read_headers(fr);
-    case READER_PUSH_PROMISE:
-        return read_push_promise(fr);
     case READER_CONTIN:
         return read_contin(fr);
     case READER_SETTINGS:

src/liblsquic/lsquic_frame_reader.h

@@ -56,7 +56,6 @@ enum frame_reader_error
 struct frame_reader_callbacks
 {
     void (*frc_on_headers)      (void *frame_cb_ctx, struct uncompressed_headers *);
-    void (*frc_on_push_promise) (void *frame_cb_ctx, struct uncompressed_headers *);
     void (*frc_on_settings)     (void *frame_cb_ctx, uint16_t setting_id,
                                  uint32_t setting_value);
     void (*frc_on_priority)     (void *frame_cb_ctx, lsquic_stream_id_t stream_id,

src/liblsquic/lsquic_frame_writer.c

@@ -487,58 +487,6 @@ lsquic_frame_writer_write_headers (struct lsquic_frame_writer *fw,
 }
 
 
-int
-lsquic_frame_writer_write_promise (struct lsquic_frame_writer *fw,
-    lsquic_stream_id_t stream_id64, lsquic_stream_id_t promised_stream_id64,
-    const struct lsquic_http_headers *headers)
-{
-    uint32_t stream_id = stream_id64;
-    uint32_t promised_stream_id = promised_stream_id64;
-    struct header_framer_ctx hfc;
-    struct http_push_promise_frame push_frame;
-    unsigned char *buf;
-    int s;
-
-    fiu_return_on("frame_writer/writer_promise", -1);
-
-    if (fw->fw_max_header_list_sz && 0 != check_headers_size(fw, headers))
-        return -1;
-
-    if (0 != check_headers_case(fw, headers))
-        return -1;
-
-    if (have_oversize_strings(headers))
-        return -1;
-
-    hfc_init(&hfc, fw, fw->fw_max_frame_sz, HTTP_FRAME_PUSH_PROMISE,
-                                                            stream_id, 0);
-
-    promised_stream_id = htonl(promised_stream_id);
-    memcpy(push_frame.hppf_promised_id, &promised_stream_id, 4);
-    s = hfc_write(&hfc, &push_frame, sizeof(struct http_push_promise_frame));
-    if (s < 0)
-        return s;
-
-    buf = malloc(MAX_COMP_HEADER_FIELD_SIZE);
-    if (!buf)
-        return -1;
-
-    s = write_headers(fw, headers, &hfc, buf, MAX_COMP_HEADER_FIELD_SIZE);
-    if (s != 0)
-    {
-        free(buf);
-        return -1;
-    }
-
-    free(buf);
-
-    EV_LOG_GENERATED_HTTP_PUSH_PROMISE(LSQUIC_LOG_CONN_ID, stream_id,
-                                        htonl(promised_stream_id), headers);
-    hfc_terminate_frame(&hfc, HFHF_END_HEADERS);
-    return lsquic_frame_writer_flush(fw);
-}
-
-
 void
 lsquic_frame_writer_max_header_list_size (struct lsquic_frame_writer *fw,
                                           uint32_t max_size)

src/liblsquic/lsquic_frame_writer.h

@@ -56,11 +56,6 @@ lsquic_frame_writer_write_priority (struct lsquic_frame_writer *,
                 lsquic_stream_id_t stream_id, int exclusive,
                 lsquic_stream_id_t stream_dep_id, unsigned priority);
 
-int
-lsquic_frame_writer_write_promise (struct lsquic_frame_writer *,
-        lsquic_stream_id_t stream_id, lsquic_stream_id_t promised_stream_id,
-        const struct lsquic_http_headers *headers);
-
 void
 lsquic_frame_writer_max_header_list_size (struct lsquic_frame_writer *,
                                           uint32_t max_size);