Adding upstream version 2.4.38.upstream/2.4.38upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1335 insertions, 0 deletions

diff --git a/modules/http2/h2_proxy_util.c b/modules/http2/h2_proxy_util.c
new file mode 100644
index 0000000..bd45294
--- /dev/null
+++ b/modules/http2/h2_proxy_util.c
@@ -0,0 +1,1335 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+ 
+#include <assert.h>
+#include <apr_lib.h>
+#include <apr_strings.h>
+#include <apr_thread_mutex.h>
+#include <apr_thread_cond.h>
+
+#include <httpd.h>
+#include <http_core.h>
+#include <http_log.h>
+#include <http_request.h>
+#include <mod_proxy.h>
+
+#include <nghttp2/nghttp2.h>
+
+#include "h2.h"
+#include "h2_proxy_util.h"
+
+APLOG_USE_MODULE(proxy_http2);
+
+/* h2_log2(n) iff n is a power of 2 */
+unsigned char h2_proxy_log2(int n)
+{
+    int lz = 0;
+    if (!n) {
+        return 0;
+    }
+    if (!(n & 0xffff0000u)) {
+        lz += 16;
+        n = (n << 16);
+    }
+    if (!(n & 0xff000000u)) {
+        lz += 8;
+        n = (n << 8);
+    }
+    if (!(n & 0xf0000000u)) {
+        lz += 4;
+        n = (n << 4);
+    }
+    if (!(n & 0xc0000000u)) {
+        lz += 2;
+        n = (n << 2);
+    }
+    if (!(n & 0x80000000u)) {
+        lz += 1;
+    }
+    
+    return 31 - lz;
+}
+
+/*******************************************************************************
+ * ihash - hash for structs with int identifier
+ ******************************************************************************/
+struct h2_proxy_ihash_t {
+    apr_hash_t *hash;
+    size_t ioff;
+};
+
+static unsigned int ihash(const char *key, apr_ssize_t *klen)
+{
+    return (unsigned int)(*((int*)key));
+}
+
+h2_proxy_ihash_t *h2_proxy_ihash_create(apr_pool_t *pool, size_t offset_of_int)
+{
+    h2_proxy_ihash_t *ih = apr_pcalloc(pool, sizeof(h2_proxy_ihash_t));
+    ih->hash = apr_hash_make_custom(pool, ihash);
+    ih->ioff = offset_of_int;
+    return ih;
+}
+
+size_t h2_proxy_ihash_count(h2_proxy_ihash_t *ih)
+{
+    return apr_hash_count(ih->hash);
+}
+
+int h2_proxy_ihash_empty(h2_proxy_ihash_t *ih)
+{
+    return apr_hash_count(ih->hash) == 0;
+}
+
+void *h2_proxy_ihash_get(h2_proxy_ihash_t *ih, int id)
+{
+    return apr_hash_get(ih->hash, &id, sizeof(id));
+}
+
+typedef struct {
+    h2_proxy_ihash_iter_t *iter;
+    void *ctx;
+} iter_ctx;
+
+static int ihash_iter(void *ctx, const void *key, apr_ssize_t klen, 
+                     const void *val)
+{
+    iter_ctx *ictx = ctx;
+    return ictx->iter(ictx->ctx, (void*)val); /* why is this passed const?*/
+}
+
+int h2_proxy_ihash_iter(h2_proxy_ihash_t *ih, h2_proxy_ihash_iter_t *fn, void *ctx)
+{
+    iter_ctx ictx;
+    ictx.iter = fn;
+    ictx.ctx = ctx;
+    return apr_hash_do(ihash_iter, &ictx, ih->hash);
+}
+
+void h2_proxy_ihash_add(h2_proxy_ihash_t *ih, void *val)
+{
+    apr_hash_set(ih->hash, ((char *)val + ih->ioff), sizeof(int), val);
+}
+
+void h2_proxy_ihash_remove(h2_proxy_ihash_t *ih, int id)
+{
+    apr_hash_set(ih->hash, &id, sizeof(id), NULL);
+}
+
+void h2_proxy_ihash_remove_val(h2_proxy_ihash_t *ih, void *val)
+{
+    int id = *((int*)((char *)val + ih->ioff));
+    apr_hash_set(ih->hash, &id, sizeof(id), NULL);
+}
+
+
+void h2_proxy_ihash_clear(h2_proxy_ihash_t *ih)
+{
+    apr_hash_clear(ih->hash);
+}
+
+typedef struct {
+    h2_proxy_ihash_t *ih;
+    void **buffer;
+    size_t max;
+    size_t len;
+} collect_ctx;
+
+static int collect_iter(void *x, void *val)
+{
+    collect_ctx *ctx = x;
+    if (ctx->len < ctx->max) {
+        ctx->buffer[ctx->len++] = val;
+        return 1;
+    }
+    return 0;
+}
+
+size_t h2_proxy_ihash_shift(h2_proxy_ihash_t *ih, void **buffer, size_t max)
+{
+    collect_ctx ctx;
+    size_t i;
+    
+    ctx.ih = ih;
+    ctx.buffer = buffer;
+    ctx.max = max;
+    ctx.len = 0;
+    h2_proxy_ihash_iter(ih, collect_iter, &ctx);
+    for (i = 0; i < ctx.len; ++i) {
+        h2_proxy_ihash_remove_val(ih, buffer[i]);
+    }
+    return ctx.len;
+}
+
+typedef struct {
+    h2_proxy_ihash_t *ih;
+    int *buffer;
+    size_t max;
+    size_t len;
+} icollect_ctx;
+
+static int icollect_iter(void *x, void *val)
+{
+    icollect_ctx *ctx = x;
+    if (ctx->len < ctx->max) {
+        ctx->buffer[ctx->len++] = *((int*)((char *)val + ctx->ih->ioff));
+        return 1;
+    }
+    return 0;
+}
+
+size_t h2_proxy_ihash_ishift(h2_proxy_ihash_t *ih, int *buffer, size_t max)
+{
+    icollect_ctx ctx;
+    size_t i;
+    
+    ctx.ih = ih;
+    ctx.buffer = buffer;
+    ctx.max = max;
+    ctx.len = 0;
+    h2_proxy_ihash_iter(ih, icollect_iter, &ctx);
+    for (i = 0; i < ctx.len; ++i) {
+        h2_proxy_ihash_remove(ih, buffer[i]);
+    }
+    return ctx.len;
+}
+
+/*******************************************************************************
+ * iqueue - sorted list of int
+ ******************************************************************************/
+
+static void iq_grow(h2_proxy_iqueue *q, int nlen);
+static void iq_swap(h2_proxy_iqueue *q, int i, int j);
+static int iq_bubble_up(h2_proxy_iqueue *q, int i, int top, 
+                        h2_proxy_iq_cmp *cmp, void *ctx);
+static int iq_bubble_down(h2_proxy_iqueue *q, int i, int bottom, 
+                          h2_proxy_iq_cmp *cmp, void *ctx);
+
+h2_proxy_iqueue *h2_proxy_iq_create(apr_pool_t *pool, int capacity)
+{
+    h2_proxy_iqueue *q = apr_pcalloc(pool, sizeof(h2_proxy_iqueue));
+    if (q) {
+        q->pool = pool;
+        iq_grow(q, capacity);
+        q->nelts = 0;
+    }
+    return q;
+}
+
+int h2_proxy_iq_empty(h2_proxy_iqueue *q)
+{
+    return q->nelts == 0;
+}
+
+int h2_proxy_iq_count(h2_proxy_iqueue *q)
+{
+    return q->nelts;
+}
+
+
+void h2_proxy_iq_add(h2_proxy_iqueue *q, int sid, h2_proxy_iq_cmp *cmp, void *ctx)
+{
+    int i;
+    
+    if (q->nelts >= q->nalloc) {
+        iq_grow(q, q->nalloc * 2);
+    }
+    
+    i = (q->head + q->nelts) % q->nalloc;
+    q->elts[i] = sid;
+    ++q->nelts;
+    
+    if (cmp) {
+        /* bubble it to the front of the queue */
+        iq_bubble_up(q, i, q->head, cmp, ctx);
+    }
+}
+
+int h2_proxy_iq_remove(h2_proxy_iqueue *q, int sid)
+{
+    int i;
+    for (i = 0; i < q->nelts; ++i) {
+        if (sid == q->elts[(q->head + i) % q->nalloc]) {
+            break;
+        }
+    }
+    
+    if (i < q->nelts) {
+        ++i;
+        for (; i < q->nelts; ++i) {
+            q->elts[(q->head+i-1)%q->nalloc] = q->elts[(q->head+i)%q->nalloc];
+        }
+        --q->nelts;
+        return 1;
+    }
+    return 0;
+}
+
+void h2_proxy_iq_clear(h2_proxy_iqueue *q)
+{
+    q->nelts = 0;
+}
+
+void h2_proxy_iq_sort(h2_proxy_iqueue *q, h2_proxy_iq_cmp *cmp, void *ctx)
+{
+    /* Assume that changes in ordering are minimal. This needs,
+     * best case, q->nelts - 1 comparisons to check that nothing
+     * changed.
+     */
+    if (q->nelts > 0) {
+        int i, ni, prev, last;
+        
+        /* Start at the end of the queue and create a tail of sorted
+         * entries. Make that tail one element longer in each iteration.
+         */
+        last = i = (q->head + q->nelts - 1) % q->nalloc;
+        while (i != q->head) {
+            prev = (q->nalloc + i - 1) % q->nalloc;
+            
+            ni = iq_bubble_up(q, i, prev, cmp, ctx);
+            if (ni == prev) {
+                /* i bubbled one up, bubble the new i down, which
+                 * keeps all tasks below i sorted. */
+                iq_bubble_down(q, i, last, cmp, ctx);
+            }
+            i = prev;
+        };
+    }
+}
+
+
+int h2_proxy_iq_shift(h2_proxy_iqueue *q)
+{
+    int sid;
+    
+    if (q->nelts <= 0) {
+        return 0;
+    }
+    
+    sid = q->elts[q->head];
+    q->head = (q->head + 1) % q->nalloc;
+    q->nelts--;
+    
+    return sid;
+}
+
+static void iq_grow(h2_proxy_iqueue *q, int nlen)
+{
+    if (nlen > q->nalloc) {
+        int *nq = apr_pcalloc(q->pool, sizeof(int) * nlen);
+        if (q->nelts > 0) {
+            int l = ((q->head + q->nelts) % q->nalloc) - q->head;
+            
+            memmove(nq, q->elts + q->head, sizeof(int) * l);
+            if (l < q->nelts) {
+                /* elts wrapped, append elts in [0, remain] to nq */
+                int remain = q->nelts - l;
+                memmove(nq + l, q->elts, sizeof(int) * remain);
+            }
+        }
+        q->elts = nq;
+        q->nalloc = nlen;
+        q->head = 0;
+    }
+}
+
+static void iq_swap(h2_proxy_iqueue *q, int i, int j)
+{
+    int x = q->elts[i];
+    q->elts[i] = q->elts[j];
+    q->elts[j] = x;
+}
+
+static int iq_bubble_up(h2_proxy_iqueue *q, int i, int top, 
+                        h2_proxy_iq_cmp *cmp, void *ctx) 
+{
+    int prev;
+    while (((prev = (q->nalloc + i - 1) % q->nalloc), i != top) 
+           && (*cmp)(q->elts[i], q->elts[prev], ctx) < 0) {
+        iq_swap(q, prev, i);
+        i = prev;
+    }
+    return i;
+}
+
+static int iq_bubble_down(h2_proxy_iqueue *q, int i, int bottom, 
+                          h2_proxy_iq_cmp *cmp, void *ctx)
+{
+    int next;
+    while (((next = (q->nalloc + i + 1) % q->nalloc), i != bottom) 
+           && (*cmp)(q->elts[i], q->elts[next], ctx) > 0) {
+        iq_swap(q, next, i);
+        i = next;
+    }
+    return i;
+}
+
+/*******************************************************************************
+ * h2_proxy_ngheader
+ ******************************************************************************/
+#define H2_HD_MATCH_LIT_CS(l, name)  \
+    ((strlen(name) == sizeof(l) - 1) && !apr_strnatcasecmp(l, name))
+
+static int h2_util_ignore_header(const char *name) 
+{
+    /* never forward, ch. 8.1.2.2 */
+    return (H2_HD_MATCH_LIT_CS("connection", name)
+            || H2_HD_MATCH_LIT_CS("proxy-connection", name)
+            || H2_HD_MATCH_LIT_CS("upgrade", name)
+            || H2_HD_MATCH_LIT_CS("keep-alive", name)
+            || H2_HD_MATCH_LIT_CS("transfer-encoding", name));
+}
+
+static int count_header(void *ctx, const char *key, const char *value)
+{
+    if (!h2_util_ignore_header(key)) {
+        (*((size_t*)ctx))++;
+    }
+    return 1;
+}
+
+#define NV_ADD_LIT_CS(nv, k, v)     add_header(nv, k, sizeof(k) - 1, v, strlen(v))
+#define NV_ADD_CS_CS(nv, k, v)      add_header(nv, k, strlen(k), v, strlen(v))
+
+static int add_header(h2_proxy_ngheader *ngh, 
+                      const char *key, size_t key_len,
+                      const char *value, size_t val_len)
+{
+    nghttp2_nv *nv = &ngh->nv[ngh->nvlen++];
+    
+    nv->name = (uint8_t*)key;
+    nv->namelen = key_len;
+    nv->value = (uint8_t*)value;
+    nv->valuelen = val_len;
+    return 1;
+}
+
+static int add_table_header(void *ctx, const char *key, const char *value)
+{
+    if (!h2_util_ignore_header(key)) {
+        add_header(ctx, key, strlen(key), value, strlen(value));
+    }
+    return 1;
+}
+
+h2_proxy_ngheader *h2_proxy_util_nghd_make_req(apr_pool_t *p, 
+                                               const h2_proxy_request *req)
+{
+    
+    h2_proxy_ngheader *ngh;
+    size_t n;
+    
+    ap_assert(req);
+    ap_assert(req->scheme);
+    ap_assert(req->authority);
+    ap_assert(req->path);
+    ap_assert(req->method);
+
+    n = 4;
+    apr_table_do(count_header, &n, req->headers, NULL);
+    
+    ngh = apr_pcalloc(p, sizeof(h2_proxy_ngheader));
+    ngh->nv =  apr_pcalloc(p, n * sizeof(nghttp2_nv));
+    NV_ADD_LIT_CS(ngh, ":scheme", req->scheme);
+    NV_ADD_LIT_CS(ngh, ":authority", req->authority);
+    NV_ADD_LIT_CS(ngh, ":path", req->path);
+    NV_ADD_LIT_CS(ngh, ":method", req->method);
+    apr_table_do(add_table_header, ngh, req->headers, NULL);
+
+    return ngh;
+}
+
+/*******************************************************************************
+ * header HTTP/1 <-> HTTP/2 conversions
+ ******************************************************************************/
+ 
+typedef struct {
+    const char *name;
+    size_t len;
+} literal;
+
+#define H2_DEF_LITERAL(n)   { (n), (sizeof(n)-1) }
+#define H2_LIT_ARGS(a)      (a),H2_ALEN(a)
+
+static literal IgnoredRequestHeaders[] = {
+    H2_DEF_LITERAL("upgrade"),
+    H2_DEF_LITERAL("connection"),
+    H2_DEF_LITERAL("keep-alive"),
+    H2_DEF_LITERAL("http2-settings"),
+    H2_DEF_LITERAL("proxy-connection"),
+    H2_DEF_LITERAL("transfer-encoding"),
+};
+static literal IgnoredProxyRespHds[] = {
+    H2_DEF_LITERAL("alt-svc"),
+};
+
+static int ignore_header(const literal *lits, size_t llen,
+                         const char *name, size_t nlen)
+{
+    const literal *lit;
+    int i;
+    
+    for (i = 0; i < llen; ++i) {
+        lit = &lits[i];
+        if (lit->len == nlen && !apr_strnatcasecmp(lit->name, name)) {
+            return 1;
+        }
+    }
+    return 0;
+}
+
+static int h2_proxy_req_ignore_header(const char *name, size_t len)
+{
+    return ignore_header(H2_LIT_ARGS(IgnoredRequestHeaders), name, len);
+}
+
+int h2_proxy_res_ignore_header(const char *name, size_t len)
+{
+    return (h2_proxy_req_ignore_header(name, len) 
+            || ignore_header(H2_LIT_ARGS(IgnoredProxyRespHds), name, len));
+}
+
+void h2_proxy_util_camel_case_header(char *s, size_t len)
+{
+    size_t start = 1;
+    size_t i;
+    for (i = 0; i < len; ++i) {
+        if (start) {
+            if (s[i] >= 'a' && s[i] <= 'z') {
+                s[i] -= 'a' - 'A';
+            }
+            
+            start = 0;
+        }
+        else if (s[i] == '-') {
+            start = 1;
+        }
+    }
+}
+
+/*******************************************************************************
+ * h2 request handling
+ ******************************************************************************/
+
+/** Match a header value against a string constance, case insensitive */
+#define H2_HD_MATCH_LIT(l, name, nlen)  \
+    ((nlen == sizeof(l) - 1) && !apr_strnatcasecmp(l, name))
+
+static apr_status_t h2_headers_add_h1(apr_table_t *headers, apr_pool_t *pool, 
+                                      const char *name, size_t nlen,
+                                      const char *value, size_t vlen)
+{
+    char *hname, *hvalue;
+    
+    if (h2_proxy_req_ignore_header(name, nlen)) {
+        return APR_SUCCESS;
+    }
+    else if (H2_HD_MATCH_LIT("cookie", name, nlen)) {
+        const char *existing = apr_table_get(headers, "cookie");
+        if (existing) {
+            char *nval;
+            
+            /* Cookie header come separately in HTTP/2, but need
+             * to be merged by "; " (instead of default ", ")
+             */
+            hvalue = apr_pstrndup(pool, value, vlen);
+            nval = apr_psprintf(pool, "%s; %s", existing, hvalue);
+            apr_table_setn(headers, "Cookie", nval);
+            return APR_SUCCESS;
+        }
+    }
+    else if (H2_HD_MATCH_LIT("host", name, nlen)) {
+        if (apr_table_get(headers, "Host")) {
+            return APR_SUCCESS; /* ignore duplicate */
+        }
+    }
+    
+    hname = apr_pstrndup(pool, name, nlen);
+    hvalue = apr_pstrndup(pool, value, vlen);
+    h2_proxy_util_camel_case_header(hname, nlen);
+    apr_table_mergen(headers, hname, hvalue);
+    
+    return APR_SUCCESS;
+}
+
+static h2_proxy_request *h2_proxy_req_createn(int id, apr_pool_t *pool, const char *method, 
+                                  const char *scheme, const char *authority, 
+                                  const char *path, apr_table_t *header, 
+                                  int serialize)
+{
+    h2_proxy_request *req = apr_pcalloc(pool, sizeof(h2_proxy_request));
+    
+    req->method         = method;
+    req->scheme         = scheme;
+    req->authority      = authority;
+    req->path           = path;
+    req->headers        = header? header : apr_table_make(pool, 10);
+    req->request_time   = apr_time_now();
+    req->serialize      = serialize;
+    
+    return req;
+}
+
+h2_proxy_request *h2_proxy_req_create(int id, apr_pool_t *pool, int serialize)
+{
+    return h2_proxy_req_createn(id, pool, NULL, NULL, NULL, NULL, NULL, serialize);
+}
+
+typedef struct {
+    apr_table_t *headers;
+    apr_pool_t *pool;
+} h1_ctx;
+
+static int set_h1_header(void *ctx, const char *key, const char *value)
+{
+    h1_ctx *x = ctx;
+    size_t klen = strlen(key);
+    if (!h2_proxy_req_ignore_header(key, klen)) {
+        h2_headers_add_h1(x->headers, x->pool, key, klen, value, strlen(value));
+    }
+    return 1;
+}
+
+apr_status_t h2_proxy_req_make(h2_proxy_request *req, apr_pool_t *pool,
+                         const char *method, const char *scheme, 
+                         const char *authority, const char *path, 
+                         apr_table_t *headers)
+{
+    h1_ctx x;
+
+    req->method    = method;
+    req->scheme    = scheme;
+    req->authority = authority;
+    req->path      = path;
+
+    ap_assert(req->scheme);
+    ap_assert(req->authority);
+    ap_assert(req->path);
+    ap_assert(req->method);
+
+    x.pool = pool;
+    x.headers = req->headers;
+    apr_table_do(set_h1_header, &x, headers, NULL);
+    return APR_SUCCESS;
+}
+
+/*******************************************************************************
+ * frame logging
+ ******************************************************************************/
+
+int h2_proxy_util_frame_print(const nghttp2_frame *frame, char *buffer, size_t maxlen)
+{
+    char scratch[128];
+    size_t s_len = sizeof(scratch)/sizeof(scratch[0]);
+    
+    switch (frame->hd.type) {
+        case NGHTTP2_DATA: {
+            return apr_snprintf(buffer, maxlen,
+                                "DATA[length=%d, flags=%d, stream=%d, padlen=%d]",
+                                (int)frame->hd.length, frame->hd.flags,
+                                frame->hd.stream_id, (int)frame->data.padlen);
+        }
+        case NGHTTP2_HEADERS: {
+            return apr_snprintf(buffer, maxlen,
+                                "HEADERS[length=%d, hend=%d, stream=%d, eos=%d]",
+                                (int)frame->hd.length,
+                                !!(frame->hd.flags & NGHTTP2_FLAG_END_HEADERS),
+                                frame->hd.stream_id,
+                                !!(frame->hd.flags & NGHTTP2_FLAG_END_STREAM));
+        }
+        case NGHTTP2_PRIORITY: {
+            return apr_snprintf(buffer, maxlen,
+                                "PRIORITY[length=%d, flags=%d, stream=%d]",
+                                (int)frame->hd.length,
+                                frame->hd.flags, frame->hd.stream_id);
+        }
+        case NGHTTP2_RST_STREAM: {
+            return apr_snprintf(buffer, maxlen,
+                                "RST_STREAM[length=%d, flags=%d, stream=%d]",
+                                (int)frame->hd.length,
+                                frame->hd.flags, frame->hd.stream_id);
+        }
+        case NGHTTP2_SETTINGS: {
+            if (frame->hd.flags & NGHTTP2_FLAG_ACK) {
+                return apr_snprintf(buffer, maxlen,
+                                    "SETTINGS[ack=1, stream=%d]",
+                                    frame->hd.stream_id);
+            }
+            return apr_snprintf(buffer, maxlen,
+                                "SETTINGS[length=%d, stream=%d]",
+                                (int)frame->hd.length, frame->hd.stream_id);
+        }
+        case NGHTTP2_PUSH_PROMISE: {
+            return apr_snprintf(buffer, maxlen,
+                                "PUSH_PROMISE[length=%d, hend=%d, stream=%d]",
+                                (int)frame->hd.length,
+                                !!(frame->hd.flags & NGHTTP2_FLAG_END_HEADERS),
+                                frame->hd.stream_id);
+        }
+        case NGHTTP2_PING: {
+            return apr_snprintf(buffer, maxlen,
+                                "PING[length=%d, ack=%d, stream=%d]",
+                                (int)frame->hd.length,
+                                frame->hd.flags&NGHTTP2_FLAG_ACK,
+                                frame->hd.stream_id);
+        }
+        case NGHTTP2_GOAWAY: {
+            size_t len = (frame->goaway.opaque_data_len < s_len)?
+                frame->goaway.opaque_data_len : s_len-1;
+            memcpy(scratch, frame->goaway.opaque_data, len);
+            scratch[len] = '\0';
+            return apr_snprintf(buffer, maxlen, "GOAWAY[error=%d, reason='%s', "
+                                "last_stream=%d]", frame->goaway.error_code, 
+                                scratch, frame->goaway.last_stream_id);
+        }
+        case NGHTTP2_WINDOW_UPDATE: {
+            return apr_snprintf(buffer, maxlen,
+                                "WINDOW_UPDATE[stream=%d, incr=%d]",
+                                frame->hd.stream_id, 
+                                frame->window_update.window_size_increment);
+        }
+        default:
+            return apr_snprintf(buffer, maxlen,
+                                "type=%d[length=%d, flags=%d, stream=%d]",
+                                frame->hd.type, (int)frame->hd.length,
+                                frame->hd.flags, frame->hd.stream_id);
+    }
+}
+
+/*******************************************************************************
+ * link header handling 
+ ******************************************************************************/
+
+typedef struct {
+    apr_pool_t *pool;
+    request_rec *r;
+    proxy_dir_conf *conf;
+    const char *s;
+    int slen;
+    int i;
+    const char *server_uri;
+    int su_len;
+    const char *real_backend_uri;
+    int rbu_len;
+    const char *p_server_uri;
+    int psu_len;
+    int link_start;
+    int link_end;
+} link_ctx;
+
+static int attr_char(char c) 
+{
+    switch (c) {
+        case '!':
+        case '#':
+        case '$':
+        case '&':
+        case '+':
+        case '-':
+        case '.':
+        case '^':
+        case '_':
+        case '`':
+        case '|':
+        case '~':
+            return 1;
+        default:
+            return apr_isalnum(c);
+    }
+}
+
+static int ptoken_char(char c) 
+{
+    switch (c) {
+        case '!':
+        case '#':
+        case '$':
+        case '&':
+        case '\'':
+        case '(':
+        case ')':
+        case '*':
+        case '+':
+        case '-':
+        case '.':
+        case '/':
+        case ':':
+        case '<':
+        case '=':
+        case '>':
+        case '?':
+        case '@':
+        case '[':
+        case ']':
+        case '^':
+        case '_':
+        case '`':
+        case '{':
+        case '|':
+        case '}':
+        case '~':
+            return 1;
+        default:
+            return apr_isalnum(c);
+    }
+}
+
+static int skip_ws(link_ctx *ctx)
+{
+    char c;
+    while (ctx->i < ctx->slen 
+           && (((c = ctx->s[ctx->i]) == ' ') || (c == '\t'))) {
+        ++ctx->i;
+    }
+    return (ctx->i < ctx->slen);
+}
+
+static int find_chr(link_ctx *ctx, char c, int *pidx)
+{
+    int j;
+    for (j = ctx->i; j < ctx->slen; ++j) {
+        if (ctx->s[j] == c) {
+            *pidx = j;
+            return 1;
+        }
+    } 
+    return 0;
+}
+
+static int read_chr(link_ctx *ctx, char c)
+{
+    if (ctx->i < ctx->slen && ctx->s[ctx->i] == c) {
+        ++ctx->i;
+        return 1;
+    }
+    return 0;
+}
+
+static int skip_qstring(link_ctx *ctx)
+{
+    if (skip_ws(ctx) && read_chr(ctx, '\"')) {
+        int end;
+        if (find_chr(ctx, '\"', &end)) {
+            ctx->i = end + 1;
+            return 1;
+        }
+    }
+    return 0;
+}
+
+static int skip_ptoken(link_ctx *ctx)
+{
+    if (skip_ws(ctx)) {
+        int i;
+        for (i = ctx->i; i < ctx->slen && ptoken_char(ctx->s[i]); ++i) {
+            /* nop */
+        }
+        if (i > ctx->i) {
+            ctx->i = i;
+            return 1;
+        }
+    }
+    return 0;
+}
+
+
+static int read_link(link_ctx *ctx)
+{
+    ctx->link_start = ctx->link_end = 0;
+    if (skip_ws(ctx) && read_chr(ctx, '<')) {
+        int end;
+        if (find_chr(ctx, '>', &end)) {
+            ctx->link_start = ctx->i;
+            ctx->link_end = end;
+            ctx->i = end + 1;
+            return 1;
+        }
+    }
+    return 0;
+}
+
+static int skip_pname(link_ctx *ctx)
+{
+    if (skip_ws(ctx)) {
+        int i;
+        for (i = ctx->i; i < ctx->slen && attr_char(ctx->s[i]); ++i) {
+            /* nop */
+        }
+        if (i > ctx->i) {
+            ctx->i = i;
+            return 1;
+        }
+    }
+    return 0;
+}
+
+static int skip_pvalue(link_ctx *ctx)
+{
+    if (skip_ws(ctx) && read_chr(ctx, '=')) {
+        if (skip_qstring(ctx) || skip_ptoken(ctx)) {
+            return 1;
+        }
+    }
+    return 0;
+}
+
+static int skip_param(link_ctx *ctx)
+{
+    if (skip_ws(ctx) && read_chr(ctx, ';')) {
+        if (skip_pname(ctx)) {
+            skip_pvalue(ctx); /* value is optional */
+            return 1;
+        }
+    }
+    return 0;
+}
+
+static int read_sep(link_ctx *ctx)
+{
+    if (skip_ws(ctx) && read_chr(ctx, ',')) {
+        return 1;
+    }
+    return 0;
+}
+
+static size_t subst_str(link_ctx *ctx, int start, int end, const char *ns)
+{
+    int olen, nlen, plen;
+    int delta;
+    char *p;
+    
+    olen = end - start;
+    nlen = (int)strlen(ns);
+    delta = nlen - olen;
+    plen = ctx->slen + delta + 1;
+    p = apr_pcalloc(ctx->pool, plen);
+    memcpy(p, ctx->s, start);
+    memcpy(p + start, ns, nlen);
+    strcpy(p + start + nlen, ctx->s + end);
+    ctx->s = p;
+    ctx->slen = (int)strlen(p);
+    if (ctx->i >= end) {
+        ctx->i += delta;
+    }
+    return nlen; 
+}
+
+static void map_link(link_ctx *ctx) 
+{
+    if (ctx->link_start < ctx->link_end) {
+        char buffer[HUGE_STRING_LEN];
+        int need_len, link_len, buffer_len, prepend_p_server; 
+        const char *mapped;
+        
+        buffer[0] = '\0';
+        buffer_len = 0;
+        link_len = ctx->link_end - ctx->link_start;
+        need_len = link_len + 1;
+        prepend_p_server = (ctx->s[ctx->link_start] == '/'); 
+        if (prepend_p_server) {
+            /* common to use relative uris in link header, for mappings
+             * to work need to prefix the backend server uri */
+            need_len += ctx->psu_len;
+            apr_cpystrn(buffer, ctx->p_server_uri, sizeof(buffer));
+            buffer_len = ctx->psu_len;
+        }
+        if (need_len > sizeof(buffer)) {
+            ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, ctx->r, APLOGNO(03482) 
+                          "link_reverse_map uri too long, skipped: %s", ctx->s);
+            return;
+        }
+        apr_cpystrn(buffer + buffer_len, ctx->s + ctx->link_start, link_len + 1);
+        if (!prepend_p_server
+            && strcmp(ctx->real_backend_uri, ctx->p_server_uri)
+            && !strncmp(buffer, ctx->real_backend_uri, ctx->rbu_len)) {
+            /* the server uri and our local proxy uri we use differ, for mapping
+             * to work, we need to use the proxy uri */
+            int path_start = ctx->link_start + ctx->rbu_len;
+            link_len -= ctx->rbu_len;
+            memcpy(buffer, ctx->p_server_uri, ctx->psu_len);
+            memcpy(buffer + ctx->psu_len, ctx->s + path_start, link_len);
+            buffer_len = ctx->psu_len + link_len;
+            buffer[buffer_len] = '\0';            
+        }
+        mapped = ap_proxy_location_reverse_map(ctx->r, ctx->conf, buffer);
+        ap_log_rerror(APLOG_MARK, APLOG_TRACE2, 0, ctx->r, 
+                      "reverse_map[%s] %s --> %s", ctx->p_server_uri, buffer, mapped);
+        if (mapped != buffer) {
+            if (prepend_p_server) {
+                if (ctx->server_uri == NULL) {
+                    ctx->server_uri = ap_construct_url(ctx->pool, "", ctx->r);
+                    ctx->su_len = (int)strlen(ctx->server_uri);
+                }
+                if (!strncmp(mapped, ctx->server_uri, ctx->su_len)) {
+                    mapped += ctx->su_len;
+                }
+            }
+            subst_str(ctx, ctx->link_start, ctx->link_end, mapped);
+        }
+    }
+}
+
+/* RFC 5988 <https://tools.ietf.org/html/rfc5988#section-6.2.1>
+  Link           = "Link" ":" #link-value
+  link-value     = "<" URI-Reference ">" *( ";" link-param )
+  link-param     = ( ( "rel" "=" relation-types )
+                 | ( "anchor" "=" <"> URI-Reference <"> )
+                 | ( "rev" "=" relation-types )
+                 | ( "hreflang" "=" Language-Tag )
+                 | ( "media" "=" ( MediaDesc | ( <"> MediaDesc <"> ) ) )
+                 | ( "title" "=" quoted-string )
+                 | ( "title*" "=" ext-value )
+                 | ( "type" "=" ( media-type | quoted-mt ) )
+                 | ( link-extension ) )
+  link-extension = ( parmname [ "=" ( ptoken | quoted-string ) ] )
+                 | ( ext-name-star "=" ext-value )
+  ext-name-star  = parmname "*" ; reserved for RFC2231-profiled
+                                ; extensions.  Whitespace NOT
+                                ; allowed in between.
+  ptoken         = 1*ptokenchar
+  ptokenchar     = "!" | "#" | "$" | "%" | "&" | "'" | "("
+                 | ")" | "*" | "+" | "-" | "." | "/" | DIGIT
+                 | ":" | "<" | "=" | ">" | "?" | "@" | ALPHA
+                 | "[" | "]" | "^" | "_" | "`" | "{" | "|"
+                 | "}" | "~"
+  media-type     = type-name "/" subtype-name
+  quoted-mt      = <"> media-type <">
+  relation-types = relation-type
+                 | <"> relation-type *( 1*SP relation-type ) <">
+  relation-type  = reg-rel-type | ext-rel-type
+  reg-rel-type   = LOALPHA *( LOALPHA | DIGIT | "." | "-" )
+  ext-rel-type   = URI
+  
+  and from <https://tools.ietf.org/html/rfc5987>
+  parmname      = 1*attr-char
+  attr-char     = ALPHA / DIGIT
+                   / "!" / "#" / "$" / "&" / "+" / "-" / "."
+                   / "^" / "_" / "`" / "|" / "~"
+ */
+
+const char *h2_proxy_link_reverse_map(request_rec *r,
+                                      proxy_dir_conf *conf, 
+                                      const char *real_backend_uri,
+                                      const char *proxy_server_uri,
+                                      const char *s)
+{
+    link_ctx ctx;
+    
+    if (r->proxyreq != PROXYREQ_REVERSE) {
+        return s;
+    }
+    memset(&ctx, 0, sizeof(ctx));
+    ctx.r = r;
+    ctx.pool = r->pool;
+    ctx.conf = conf;
+    ctx.real_backend_uri = real_backend_uri;
+    ctx.rbu_len = (int)strlen(ctx.real_backend_uri);
+    ctx.p_server_uri = proxy_server_uri;
+    ctx.psu_len = (int)strlen(ctx.p_server_uri);
+    ctx.s = s;
+    ctx.slen = (int)strlen(s);
+    while (read_link(&ctx)) {
+        while (skip_param(&ctx)) {
+            /* nop */
+        }
+        map_link(&ctx);
+        if (!read_sep(&ctx)) {
+            break;
+        }
+    }
+    ap_log_rerror(APLOG_MARK, APLOG_TRACE2, 0, r, 
+                  "link_reverse_map %s --> %s", s, ctx.s);
+    return ctx.s;
+}
+
+/*******************************************************************************
+ * FIFO queue
+ ******************************************************************************/
+
+struct h2_proxy_fifo {
+    void **elems;
+    int nelems;
+    int set;
+    int head;
+    int count;
+    int aborted;
+    apr_thread_mutex_t *lock;
+    apr_thread_cond_t  *not_empty;
+    apr_thread_cond_t  *not_full;
+};
+
+static int nth_index(h2_proxy_fifo *fifo, int n) 
+{
+    return (fifo->head + n) % fifo->nelems;
+}
+
+static apr_status_t fifo_destroy(void *data) 
+{
+    h2_proxy_fifo *fifo = data;
+
+    apr_thread_cond_destroy(fifo->not_empty);
+    apr_thread_cond_destroy(fifo->not_full);
+    apr_thread_mutex_destroy(fifo->lock);
+
+    return APR_SUCCESS;
+}
+
+static int index_of(h2_proxy_fifo *fifo, void *elem)
+{
+    int i;
+    
+    for (i = 0; i < fifo->count; ++i) {
+        if (elem == fifo->elems[nth_index(fifo, i)]) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+static apr_status_t create_int(h2_proxy_fifo **pfifo, apr_pool_t *pool, 
+                               int capacity, int as_set)
+{
+    apr_status_t rv;
+    h2_proxy_fifo *fifo;
+    
+    fifo = apr_pcalloc(pool, sizeof(*fifo));
+    if (fifo == NULL) {
+        return APR_ENOMEM;
+    }
+
+    rv = apr_thread_mutex_create(&fifo->lock,
+                                 APR_THREAD_MUTEX_UNNESTED, pool);
+    if (rv != APR_SUCCESS) {
+        return rv;
+    }
+
+    rv = apr_thread_cond_create(&fifo->not_empty, pool);
+    if (rv != APR_SUCCESS) {
+        return rv;
+    }
+
+    rv = apr_thread_cond_create(&fifo->not_full, pool);
+    if (rv != APR_SUCCESS) {
+        return rv;
+    }
+
+    fifo->elems = apr_pcalloc(pool, capacity * sizeof(void*));
+    if (fifo->elems == NULL) {
+        return APR_ENOMEM;
+    }
+    fifo->nelems = capacity;
+    fifo->set = as_set;
+    
+    *pfifo = fifo;
+    apr_pool_cleanup_register(pool, fifo, fifo_destroy, apr_pool_cleanup_null);
+
+    return APR_SUCCESS;
+}
+
+apr_status_t h2_proxy_fifo_create(h2_proxy_fifo **pfifo, apr_pool_t *pool, int capacity)
+{
+    return create_int(pfifo, pool, capacity, 0);
+}
+
+apr_status_t h2_proxy_fifo_set_create(h2_proxy_fifo **pfifo, apr_pool_t *pool, int capacity)
+{
+    return create_int(pfifo, pool, capacity, 1);
+}
+
+apr_status_t h2_proxy_fifo_term(h2_proxy_fifo *fifo)
+{
+    apr_status_t rv;
+    if ((rv = apr_thread_mutex_lock(fifo->lock)) == APR_SUCCESS) {
+        fifo->aborted = 1;
+        apr_thread_mutex_unlock(fifo->lock);
+    }
+    return rv;
+}
+
+apr_status_t h2_proxy_fifo_interrupt(h2_proxy_fifo *fifo)
+{
+    apr_status_t rv;
+    if ((rv = apr_thread_mutex_lock(fifo->lock)) == APR_SUCCESS) {
+        apr_thread_cond_broadcast(fifo->not_empty);
+        apr_thread_cond_broadcast(fifo->not_full);
+        apr_thread_mutex_unlock(fifo->lock);
+    }
+    return rv;
+}
+
+int h2_proxy_fifo_count(h2_proxy_fifo *fifo)
+{
+    return fifo->count;
+}
+
+int h2_proxy_fifo_capacity(h2_proxy_fifo *fifo)
+{
+    return fifo->nelems;
+}
+
+static apr_status_t check_not_empty(h2_proxy_fifo *fifo, int block)
+{
+    if (fifo->count == 0) {
+        if (!block) {
+            return APR_EAGAIN;
+        }
+        while (fifo->count == 0) {
+            if (fifo->aborted) {
+                return APR_EOF;
+            }
+            apr_thread_cond_wait(fifo->not_empty, fifo->lock);
+        }
+    }
+    return APR_SUCCESS;
+}
+
+static apr_status_t fifo_push(h2_proxy_fifo *fifo, void *elem, int block)
+{
+    apr_status_t rv;
+    
+    if (fifo->aborted) {
+        return APR_EOF;
+    }
+
+    if ((rv = apr_thread_mutex_lock(fifo->lock)) == APR_SUCCESS) {
+        if (fifo->set && index_of(fifo, elem) >= 0) {
+            /* set mode, elem already member */
+            apr_thread_mutex_unlock(fifo->lock);
+            return APR_EEXIST;
+        }
+        else if (fifo->count == fifo->nelems) {
+            if (block) {
+                while (fifo->count == fifo->nelems) {
+                    if (fifo->aborted) {
+                        apr_thread_mutex_unlock(fifo->lock);
+                        return APR_EOF;
+                    }
+                    apr_thread_cond_wait(fifo->not_full, fifo->lock);
+                }
+            }
+            else {
+                apr_thread_mutex_unlock(fifo->lock);
+                return APR_EAGAIN;
+            }
+        }
+        
+        ap_assert(fifo->count < fifo->nelems);
+        fifo->elems[nth_index(fifo, fifo->count)] = elem;
+        ++fifo->count;
+        if (fifo->count == 1) {
+            apr_thread_cond_broadcast(fifo->not_empty);
+        }
+        apr_thread_mutex_unlock(fifo->lock);
+    }
+    return rv;
+}
+
+apr_status_t h2_proxy_fifo_push(h2_proxy_fifo *fifo, void *elem)
+{
+    return fifo_push(fifo, elem, 1);
+}
+
+apr_status_t h2_proxy_fifo_try_push(h2_proxy_fifo *fifo, void *elem)
+{
+    return fifo_push(fifo, elem, 0);
+}
+
+static void *pull_head(h2_proxy_fifo *fifo)
+{
+    void *elem;
+    
+    ap_assert(fifo->count > 0);
+    elem = fifo->elems[fifo->head];
+    --fifo->count;
+    if (fifo->count > 0) {
+        fifo->head = nth_index(fifo, 1);
+        if (fifo->count+1 == fifo->nelems) {
+            apr_thread_cond_broadcast(fifo->not_full);
+        }
+    }
+    return elem;
+}
+
+static apr_status_t fifo_pull(h2_proxy_fifo *fifo, void **pelem, int block)
+{
+    apr_status_t rv;
+    
+    if (fifo->aborted) {
+        return APR_EOF;
+    }
+    
+    if ((rv = apr_thread_mutex_lock(fifo->lock)) == APR_SUCCESS) {
+        if ((rv = check_not_empty(fifo, block)) != APR_SUCCESS) {
+            apr_thread_mutex_unlock(fifo->lock);
+            *pelem = NULL;
+            return rv;
+        }
+
+        ap_assert(fifo->count > 0);
+        *pelem = pull_head(fifo);
+
+        apr_thread_mutex_unlock(fifo->lock);
+    }
+    return rv;
+}
+
+apr_status_t h2_proxy_fifo_pull(h2_proxy_fifo *fifo, void **pelem)
+{
+    return fifo_pull(fifo, pelem, 1);
+}
+
+apr_status_t h2_proxy_fifo_try_pull(h2_proxy_fifo *fifo, void **pelem)
+{
+    return fifo_pull(fifo, pelem, 0);
+}
+
+apr_status_t h2_proxy_fifo_remove(h2_proxy_fifo *fifo, void *elem)
+{
+    apr_status_t rv;
+    
+    if (fifo->aborted) {
+        return APR_EOF;
+    }
+
+    if ((rv = apr_thread_mutex_lock(fifo->lock)) == APR_SUCCESS) {
+        int i, rc;
+        void *e;
+        
+        rc = 0;
+        for (i = 0; i < fifo->count; ++i) {
+            e = fifo->elems[nth_index(fifo, i)];
+            if (e == elem) {
+                ++rc;
+            }
+            else if (rc) {
+                fifo->elems[nth_index(fifo, i-rc)] = e;
+            }
+        }
+        if (rc) {
+            fifo->count -= rc;
+            if (fifo->count + rc == fifo->nelems) {
+                apr_thread_cond_broadcast(fifo->not_full);
+            }
+            rv = APR_SUCCESS;
+        }
+        else {
+            rv = APR_EAGAIN;
+        }
+        
+        apr_thread_mutex_unlock(fifo->lock);
+    }
+    return rv;
+}