alt-svc: the libcurl bits

10 files changed, 736 insertions, 4 deletions

diff --git a/lib/Makefile.inc b/lib/Makefile.inc
index ce8b36eee..6c47bcda5 100644
--- a/lib/Makefile.inc
+++ b/lib/Makefile.inc
@@ -55,7 +55,7 @@ LIB_CFILES = file.c timeval.c base64.c hostip.c progress.c formdata.c   \
   curl_multibyte.c hostcheck.c conncache.c pipeline.c dotdot.c          \
   x509asn1.c http2.c smb.c curl_endian.c curl_des.c system_win32.c      \
   mime.c sha256.c setopt.c curl_path.c curl_ctype.c curl_range.c psl.c  \
-  doh.c urlapi.c
+  doh.c urlapi.c altsvc.c
 
 LIB_HFILES = arpa_telnet.h netrc.h file.h timeval.h hostip.h progress.h \
   formdata.h cookie.h http.h sendf.h ftp.h url.h dict.h if2ip.h         \
@@ -75,7 +75,8 @@ LIB_HFILES = arpa_telnet.h netrc.h file.h timeval.h hostip.h progress.h \
   curl_setup_once.h multihandle.h setup-vms.h pipeline.h dotdot.h       \
   x509asn1.h http2.h sigpipe.h smb.h curl_endian.h curl_des.h           \
   curl_printf.h system_win32.h rand.h mime.h curl_sha256.h setopt.h     \
-  curl_path.h curl_ctype.h curl_range.h psl.h doh.h urlapi-int.h
+  curl_path.h curl_ctype.h curl_range.h psl.h doh.h urlapi-int.h        \
+  altsvc.h
 
 LIB_RCFILES = libcurl.rc
 
diff --git a/lib/altsvc.c b/lib/altsvc.c
new file mode 100644
index 000000000..97cdc7b8a
--- /dev/null
+++ b/lib/altsvc.c
@@ -0,0 +1,569 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+/*
+ * The Alt-Svc: header is defined in RFC 7838:
+ * https://tools.ietf.org/html/rfc7838
+ */
+#include "curl_setup.h"
+
+#if !defined(CURL_DISABLE_HTTP) && defined(USE_ALTSVC)
+#include <curl/curl.h>
+#include "urldata.h"
+#include "altsvc.h"
+#include "cookie.h" /* for Curl_get_line() */
+#include "strcase.h"
+#include "parsedate.h"
+#include "sendf.h"
+#include "warnless.h"
+
+/* The last 3 #include files should be in this order */
+#include "curl_printf.h"
+#include "curl_memory.h"
+#include "memdebug.h"
+
+#define MAX_ALTSVC_LINE 4095
+#define MAX_ALTSVC_DATELENSTR "64"
+#define MAX_ALTSVC_DATELEN 64
+#define MAX_ALTSVC_HOSTLENSTR "512"
+#define MAX_ALTSVC_HOSTLEN 512
+#define MAX_ALTSVC_ALPNLENSTR "10"
+#define MAX_ALTSVC_ALPNLEN 10
+
+static enum alpnid alpn2alpnid(char *name)
+{
+  if(strcasecompare(name, "h1"))
+    return ALPN_h1;
+  if(strcasecompare(name, "h2"))
+    return ALPN_h2;
+  if(strcasecompare(name, "h2c"))
+    return ALPN_h2c;
+  if(strcasecompare(name, "h3"))
+    return ALPN_h3;
+  return ALPN_none; /* unknown, probably rubbish input */
+}
+
+/* Given the ALPN ID, return the name */
+const char *Curl_alpnid2str(enum alpnid id)
+{
+  switch(id) {
+  case ALPN_h1:
+    return "h1";
+  case ALPN_h2:
+    return "h2";
+  case ALPN_h2c:
+    return "h2c";
+  case ALPN_h3:
+    return "h3";
+  default:
+    return ""; /* bad */
+  }
+}
+
+
+static void altsvc_free(struct altsvc *as)
+{
+  free(as->srchost);
+  free(as->dsthost);
+  free(as);
+}
+
+static struct altsvc *altsvc_createid(const char *srchost,
+                                      const char *dsthost,
+                                      enum alpnid srcalpnid,
+                                      enum alpnid dstalpnid,
+                                      unsigned int srcport,
+                                      unsigned int dstport)
+{
+  struct altsvc *as = calloc(sizeof(struct altsvc), 1);
+  if(!as)
+    return NULL;
+
+  as->srchost = strdup(srchost);
+  if(!as->srchost)
+    goto error;
+  as->dsthost = strdup(dsthost);
+  if(!as->dsthost)
+    goto error;
+
+  as->srcalpnid = srcalpnid;
+  as->dstalpnid = dstalpnid;
+  as->srcport = curlx_ultous(srcport);
+  as->dstport = curlx_ultous(dstport);
+
+  return as;
+  error:
+  altsvc_free(as);
+  return NULL;
+}
+
+static struct altsvc *altsvc_create(char *srchost,
+                                    char *dsthost,
+                                    char *srcalpn,
+                                    char *dstalpn,
+                                    unsigned int srcport,
+                                    unsigned int dstport)
+{
+  enum alpnid dstalpnid = alpn2alpnid(dstalpn);
+  enum alpnid srcalpnid = alpn2alpnid(srcalpn);
+  if(!srcalpnid || !dstalpnid)
+    return NULL;
+  return altsvc_createid(srchost, dsthost, srcalpnid, dstalpnid,
+                         srcport, dstport);
+}
+
+/* only returns SERIOUS errors */
+static CURLcode altsvc_add(struct altsvcinfo *asi, char *line)
+{
+  /* Example line:
+     h2 example.com 443 h3 shiny.example.com 8443 "20191231 10:00:00" 1
+   */
+  char srchost[MAX_ALTSVC_HOSTLEN + 1];
+  char dsthost[MAX_ALTSVC_HOSTLEN + 1];
+  char srcalpn[MAX_ALTSVC_ALPNLEN + 1];
+  char dstalpn[MAX_ALTSVC_ALPNLEN + 1];
+  char date[MAX_ALTSVC_DATELEN + 1];
+  unsigned int srcport;
+  unsigned int dstport;
+  unsigned int prio;
+  unsigned int persist;
+  int rc;
+
+  rc = sscanf(line,
+              "%" MAX_ALTSVC_ALPNLENSTR "s %" MAX_ALTSVC_HOSTLENSTR "s %u "
+              "%" MAX_ALTSVC_ALPNLENSTR "s %" MAX_ALTSVC_HOSTLENSTR "s %u "
+              "\"%" MAX_ALTSVC_DATELENSTR "[^\"]\" %u %u",
+              srcalpn, srchost, &srcport,
+              dstalpn, dsthost, &dstport,
+              date, &persist, &prio);
+  if(9 == rc) {
+    struct altsvc *as;
+    time_t expires = curl_getdate(date, NULL);
+    as = altsvc_create(srchost, dsthost, srcalpn, dstalpn, srcport, dstport);
+    if(as) {
+      as->expires = expires;
+      as->prio = prio;
+      as->persist = persist ? 1 : 0;
+      Curl_llist_insert_next(&asi->list, asi->list.tail, as, &as->node);
+      asi->num++; /* one more entry */
+    }
+  }
+
+  return CURLE_OK;
+}
+
+/*
+ * Load alt-svc entries from the given file. The text based line-oriented file
+ * format is documented here:
+ * https://github.com/curl/curl/wiki/QUIC-implementation
+ *
+ * This function only returns error on major problems that prevents alt-svc
+ * handling to work completely. It will ignore individual syntactical errors
+ * etc.
+ */
+static CURLcode altsvc_load(struct altsvcinfo *asi, const char *file)
+{
+  CURLcode result = CURLE_OK;
+  char *line = NULL;
+  FILE *fp = fopen(file, FOPEN_READTEXT);
+  if(fp) {
+    line = malloc(MAX_ALTSVC_LINE);
+    if(!line)
+      goto fail;
+    while(Curl_get_line(line, MAX_ALTSVC_LINE, fp)) {
+      char *lineptr = line;
+      while(*lineptr && ISBLANK(*lineptr))
+        lineptr++;
+      if(*lineptr == '#')
+        /* skip commented lines */
+        continue;
+
+      altsvc_add(asi, lineptr);
+    }
+    free(line); /* free the line buffer */
+    fclose(fp);
+  }
+  return result;
+
+  fail:
+  free(line);
+  fclose(fp);
+  return CURLE_OUT_OF_MEMORY;
+}
+
+/*
+ * Write this single altsvc entry to a single output line
+ */
+
+static CURLcode altsvc_out(struct altsvc *as, FILE *fp)
+{
+  struct tm stamp;
+  Curl_gmtime(as->expires, &stamp);
+
+  fprintf(fp,
+          "%s %s %u "
+          "%s %s %u "
+          "\"%d%02d%02d "
+          "%02d:%02d:%02d\" "
+          "%u %d\n",
+          Curl_alpnid2str(as->srcalpnid), as->srchost, as->srcport,
+          Curl_alpnid2str(as->dstalpnid), as->dsthost, as->dstport,
+          stamp.tm_year + 1900, stamp.tm_mon + 1, stamp.tm_mday,
+          stamp.tm_hour, stamp.tm_min, stamp.tm_sec,
+          as->persist, as->prio);
+  return CURLE_OK;
+}
+
+/* ---- library-wide functions below ---- */
+
+/*
+ * Curl_altsvc_init() creates a new altsvc cache.
+ * It returns the new instance or NULL if something goes wrong.
+ */
+struct altsvcinfo *Curl_altsvc_init(void)
+{
+  struct altsvcinfo *asi = calloc(sizeof(struct altsvcinfo), 1);
+  if(!asi)
+    return NULL;
+  Curl_llist_init(&asi->list, NULL);
+
+  /* set default behavior */
+  asi->flags = CURLALTSVC_H1
+#ifdef USE_NGHTTP2
+    | CURLALTSVC_H2
+#endif
+#ifdef USE_HTTP3
+    /* TODO: adjust when known */
+    | CURLALTSVC_H3
+#endif
+    ;
+  return asi;
+}
+
+/*
+ * Curl_altsvc_load() loads alt-svc from file.
+ */
+CURLcode Curl_altsvc_load(struct altsvcinfo *asi, const char *file)
+{
+  CURLcode result;
+  DEBUGASSERT(asi);
+  result = altsvc_load(asi, file);
+  return result;
+}
+
+/*
+ * Curl_altsvc_ctrl() passes on the external bitmask.
+ */
+CURLcode Curl_altsvc_ctrl(struct altsvcinfo *asi, const long ctrl)
+{
+  DEBUGASSERT(asi);
+  if(!ctrl)
+    /* unexpected */
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  asi->flags = ctrl;
+  return CURLE_OK;
+}
+
+/*
+ * Curl_altsvc_cleanup() frees an altsvc cache instance and all associated
+ * resources.
+ */
+void Curl_altsvc_cleanup(struct altsvcinfo *altsvc)
+{
+  struct curl_llist_element *e;
+  struct curl_llist_element *n;
+  if(altsvc) {
+    for(e = altsvc->list.head; e; e = n) {
+      struct altsvc *as = e->ptr;
+      n = e->next;
+      altsvc_free(as);
+    }
+    free(altsvc);
+  }
+}
+
+/*
+ * Curl_altsvc_save() writes the altsvc cache to a file.
+ */
+CURLcode Curl_altsvc_save(struct altsvcinfo *altsvc, const char *file)
+{
+  struct curl_llist_element *e;
+  struct curl_llist_element *n;
+  CURLcode result = CURLE_OK;
+  FILE *out;
+
+  if(!altsvc)
+    /* no cache activated */
+    return CURLE_OK;
+
+  if((altsvc->flags & CURLALTSVC_READONLYFILE) || !file[0])
+    /* marked as read-only or zero length file name */
+    return CURLE_OK;
+  out = fopen(file, FOPEN_WRITETEXT);
+  if(!out)
+    return CURLE_WRITE_ERROR;
+  fputs("# Your alt-svc cache. https://curl.haxx.se/docs/alt-svc.html\n"
+        "# This file was generated by libcurl! Edit at your own risk.\n",
+        out);
+  for(e = altsvc->list.head; e; e = n) {
+    struct altsvc *as = e->ptr;
+    n = e->next;
+    result = altsvc_out(as, out);
+    if(result)
+      break;
+  }
+  fclose(out);
+  return result;
+}
+
+static CURLcode getalnum(const char **ptr, char *alpnbuf, size_t buflen)
+{
+  size_t len;
+  const char *protop;
+  const char *p = *ptr;
+  while(*p && ISBLANK(*p))
+    p++;
+  protop = p;
+  while(*p && ISALNUM(*p))
+    p++;
+  len = p - protop;
+
+  if(!len || (len >= buflen))
+    return CURLE_BAD_FUNCTION_ARGUMENT; /* TODO: improve error code */
+  memcpy(alpnbuf, protop, len);
+  alpnbuf[len] = 0;
+  *ptr = p;
+  return CURLE_OK;
+}
+
+/* altsvc_flush() removes all alternatives for this source origin from the
+   list */
+static void altsvc_flush(struct altsvcinfo *asi, enum alpnid srcalpnid,
+                         const char *srchost, unsigned short srcport)
+{
+  struct curl_llist_element *e;
+  struct curl_llist_element *n;
+  for(e = asi->list.head; e; e = n) {
+    struct altsvc *as = e->ptr;
+    n = e->next;
+    if((srcalpnid == as->srcalpnid) &&
+       (srcport == as->srcport) &&
+       strcasecompare(srchost, as->srchost)) {
+      Curl_llist_remove(&asi->list, e, NULL);
+      altsvc_free(as);
+      asi->num--;
+    }
+  }
+}
+
+#ifdef DEBUGBUILD
+/* to play well with debug builds, we can *set* a fixed time this will
+   return */
+static time_t debugtime(void *unused)
+{
+  char *timestr = getenv("CURL_TIME");
+  (void)unused;
+  if(timestr) {
+    unsigned long val = strtol(timestr, NULL, 10);
+    return (time_t)val;
+  }
+  return time(NULL);
+}
+#define time(x) debugtime(x)
+#endif
+
+/*
+ * Curl_altsvc_parse() takes an incoming alt-svc response header and stores
+ * the data correctly in the cache.
+ *
+ * 'value' points to the header *value*. That's contents to the right of the
+ * header name.
+ */
+CURLcode Curl_altsvc_parse(struct Curl_easy *data,
+                           struct altsvcinfo *asi, const char *value,
+                           enum alpnid srcalpnid, const char *srchost,
+                           unsigned short srcport)
+{
+  const char *p = value;
+  size_t len;
+  enum alpnid dstalpnid = srcalpnid; /* the same by default */
+  char namebuf[MAX_ALTSVC_HOSTLEN] = "";
+  char alpnbuf[MAX_ALTSVC_ALPNLEN] = "";
+  struct altsvc *as;
+  unsigned short dstport = srcport; /* the same by default */
+  const char *semip;
+  time_t maxage = 24 * 3600; /* default is 24 hours */
+  bool persist = FALSE;
+  CURLcode result = getalnum(&p, alpnbuf, sizeof(alpnbuf));
+  if(result)
+    return result;
+
+  DEBUGASSERT(asi);
+
+  /* Flush all cached alternatives for this source origin, if any */
+  altsvc_flush(asi, srcalpnid, srchost, srcport);
+
+  /* "clear" is a magic keyword */
+  if(strcasecompare(alpnbuf, "clear")) {
+    /* TODO: clear whatever it is it should clear */
+    return CURLE_OK;
+  }
+
+  /* The 'ma' and 'persist' flags are annoyingly meant for all alternatives
+     but are set after the list on the line. Scan for the semicolons and get
+     those fields first! */
+  semip = p;
+  do {
+    semip = strchr(semip, ';');
+    if(semip) {
+      char option[32];
+      unsigned long num;
+      char *end_ptr;
+      semip++; /* pass the semicolon */
+      result = getalnum(&semip, option, sizeof(option));
+      if(result)
+        break;
+      while(*semip && ISBLANK(*semip))
+        semip++;
+      if(*semip != '=')
+        continue;
+      semip++;
+      num = strtoul(semip, &end_ptr, 10);
+      if(num < ULONG_MAX) {
+        if(strcasecompare("ma", option))
+          maxage = num;
+        else if(strcasecompare("persist", option) && (num == 1))
+          persist = TRUE;
+      }
+      semip = end_ptr;
+    }
+  } while(semip);
+
+  do {
+    if(*p == '=') {
+      /* [protocol]="[host][:port]" */
+      dstalpnid = alpn2alpnid(alpnbuf);
+      if(!dstalpnid) {
+        infof(data, "Unknown alt-svc protocol \"%s\", ignoring...\n", alpnbuf);
+        return CURLE_OK;
+      }
+      p++;
+      if(*p == '\"') {
+        const char *dsthost;
+        p++;
+        if(*p != ':') {
+          /* host name starts here */
+          const char *hostp = p;
+          while(*p && (ISALNUM(*p) || (*p == '.') || (*p == '-')))
+            p++;
+          len = p - hostp;
+          if(!len || (len >= MAX_ALTSVC_HOSTLEN))
+            return CURLE_BAD_FUNCTION_ARGUMENT; /* TODO: improve error code */
+          memcpy(namebuf, hostp, len);
+          namebuf[len] = 0;
+          dsthost = namebuf;
+        }
+        else {
+          /* no destination name, use source host */
+          dsthost = srchost;
+        }
+        if(*p == ':') {
+          /* a port number */
+          char *end_ptr;
+          unsigned long port = strtoul(++p, &end_ptr, 10);
+          if(port > USHRT_MAX || end_ptr == p || *end_ptr != '\"') {
+            infof(data, "Unknown alt-svc port number, ignoring...\n");
+            return CURLE_OK;
+          }
+          p = end_ptr;
+          dstport = curlx_ultous(port);
+        }
+        if(*p++ != '\"')
+          return CURLE_BAD_FUNCTION_ARGUMENT;
+        as = altsvc_createid(srchost, dsthost,
+                             srcalpnid, dstalpnid,
+                             srcport, dstport);
+        if(as) {
+          /* TODO: the expires time also needs to take the Age: value (if any)
+             into account. [See RFC 7838 section 3.1] */
+          as->expires = maxage + time(NULL);
+          as->persist = persist;
+          Curl_llist_insert_next(&asi->list, asi->list.tail, as, &as->node);
+          asi->num++; /* one more entry */
+          infof(data, "Added alt-svc: %s:%d over %s\n", dsthost, dstport,
+                Curl_alpnid2str(dstalpnid));
+        }
+      }
+      /* after the double quote there can be a comma if there's another
+         string or a semicolon if no more */
+      if(*p == ',') {
+        /* comma means another alternative is presented */
+        p++;
+        result = getalnum(&p, alpnbuf, sizeof(alpnbuf));
+        if(result)
+          /* failed to parse, but since we alredy did at least one host we
+             return OK */
+          return CURLE_OK;
+      }
+    }
+  } while(*p && (*p != ';') && (*p != '\n') && (*p != '\r'));
+
+  return CURLE_OK;
+}
+
+/*
+ * Return TRUE on a match
+ */
+bool Curl_altsvc_lookup(struct altsvcinfo *asi,
+                        enum alpnid srcalpnid, const char *srchost,
+                        int srcport,
+                        enum alpnid *dstalpnid, const char **dsthost,
+                        int *dstport)
+{
+  struct curl_llist_element *e;
+  struct curl_llist_element *n;
+  time_t now = time(NULL);
+  DEBUGASSERT(asi);
+  DEBUGASSERT(srchost);
+  DEBUGASSERT(dsthost);
+
+  for(e = asi->list.head; e; e = n) {
+    struct altsvc *as = e->ptr;
+    n = e->next;
+    if(as->expires < now) {
+      /* an expired entry, remove */
+      altsvc_free(as);
+      continue;
+    }
+    if((as->srcalpnid == srcalpnid) &&
+       strcasecompare(as->srchost, srchost) &&
+       as->srcport == srcport) {
+      /* match */
+      *dstalpnid = as->dstalpnid;
+      *dsthost = as->dsthost;
+      *dstport = as->dstport;
+      return TRUE;
+    }
+  }
+  return FALSE;
+}
+
+#endif /* CURL_DISABLE_HTTP || USE_ALTSVC */
diff --git a/lib/altsvc.h b/lib/altsvc.h
new file mode 100644
index 000000000..eefb45bf6
--- /dev/null
+++ b/lib/altsvc.h
@@ -0,0 +1,77 @@
+#ifndef HEADER_CURL_ALTSVC_H
+#define HEADER_CURL_ALTSVC_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "curl_setup.h"
+
+#if !defined(CURL_DISABLE_HTTP) && defined(USE_ALTSVC)
+#include <curl/curl.h>
+#include "llist.h"
+
+enum alpnid {
+  ALPN_none,
+  ALPN_h1,
+  ALPN_h2,
+  ALPN_h2c,
+  ALPN_h3
+};
+
+struct altsvc {
+  char *srchost;
+  char *dsthost;
+  unsigned short srcport;
+  unsigned short dstport;
+  enum alpnid srcalpnid;
+  enum alpnid dstalpnid;
+  time_t expires;
+  bool persist;
+  int prio;
+  struct curl_llist_element node;
+};
+
+struct altsvcinfo {
+  char *filename;
+  struct curl_llist list; /* list of entries */
+  size_t num; /* number of alt-svc entries */
+  long flags; /* the publicly set bitmask */
+};
+
+const char *Curl_alpnid2str(enum alpnid id);
+struct altsvcinfo *Curl_altsvc_init(void);
+CURLcode Curl_altsvc_load(struct altsvcinfo *asi, const char *file);
+CURLcode Curl_altsvc_save(struct altsvcinfo *asi, const char *file);
+CURLcode Curl_altsvc_ctrl(struct altsvcinfo *asi, const long ctrl);
+void Curl_altsvc_cleanup(struct altsvcinfo *altsvc);
+CURLcode Curl_altsvc_parse(struct Curl_easy *data,
+                           struct altsvcinfo *altsvc, const char *value,
+                           enum alpnid srcalpn, const char *srchost,
+                           unsigned short srcport);
+bool Curl_altsvc_lookup(struct altsvcinfo *asi,
+                        enum alpnid srcalpnid, const char *srchost,
+                        int srcport,
+                        enum alpnid *dstalpnid, const char **dsthost,
+                        int *dstport);
+#else
+/* disabled */
+#define Curl_altsvc_save(a,b)
+#endif /* CURL_DISABLE_HTTP || USE_ALTSVC */
+#endif /* HEADER_CURL_ALTSVC_H */
diff --git a/lib/cookie.c b/lib/cookie.c
index 65cc11732..b24aaf718 100644
--- a/lib/cookie.c
+++ b/lib/cookie.c
@@ -1092,7 +1092,7 @@ Curl_cookie_add(struct Curl_easy *data,
  * get_line() makes sure to only return complete whole lines that fit in 'len'
  * bytes and end with a newline.
  */
-static char *get_line(char *buf, int len, FILE *input)
+char *Curl_get_line(char *buf, int len, FILE *input)
 {
   bool partial = FALSE;
   while(1) {
@@ -1172,7 +1172,7 @@ struct CookieInfo *Curl_cookie_init(struct Curl_easy *data,
     line = malloc(MAX_COOKIE_LINE);
     if(!line)
       goto fail;
-    while(get_line(line, MAX_COOKIE_LINE, fp)) {
+    while(Curl_get_line(line, MAX_COOKIE_LINE, fp)) {
       if(checkprefix("Set-Cookie:", line)) {
         /* This is a cookie line, get it! */
         lineptr = &line[11];
diff --git a/lib/cookie.h b/lib/cookie.h
index b2730cfb9..6ac4a6ac0 100644
--- a/lib/cookie.h
+++ b/lib/cookie.h
@@ -101,6 +101,7 @@ struct Cookie *Curl_cookie_getlist(struct CookieInfo *, const char *,
 void Curl_cookie_freelist(struct Cookie *cookies);
 void Curl_cookie_clearall(struct CookieInfo *cookies);
 void Curl_cookie_clearsess(struct CookieInfo *cookies);
+char *Curl_get_line(char *buf, int len, FILE *input);
 
 #if defined(CURL_DISABLE_HTTP) || defined(CURL_DISABLE_COOKIES)
 #define Curl_cookie_list(x) NULL
diff --git a/lib/http.c b/lib/http.c
index d0a01979d..f5709b68b 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -77,6 +77,7 @@
 #include "http2.h"
 #include "connect.h"
 #include "strdup.h"
+#include "altsvc.h"
 
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
@@ -3978,6 +3979,20 @@ CURLcode Curl_http_readwrite_headers(struct Curl_easy *data,
         }
       }
     }
+#ifdef USE_ALTSVC
+    /* If enabled, the header is incoming and this is over HTTPS */
+    else if(data->asi && checkprefix("Alt-Svc:", k->p) &&
+            (conn->handler->flags & PROTOPT_SSL)) {
+      /* the ALPN of the current request */
+      enum alpnid id = (conn->httpversion == 20) ? ALPN_h2 : ALPN_h1;
+      result = Curl_altsvc_parse(data, data->asi,
+                                 &k->p[ strlen("Alt-Svc:") ],
+                                 id, conn->host.name,
+                                 curlx_uitous(conn->remote_port));
+      if(result)
+        return result;
+    }
+#endif
     else if(conn->handler->protocol & CURLPROTO_RTSP) {
       result = Curl_rtsp_parseheader(conn, k->p);
       if(result)
diff --git a/lib/setopt.c b/lib/setopt.c
index fdcbfacae..b5f74a93d 100644
--- a/lib/setopt.c
+++ b/lib/setopt.c
@@ -44,6 +44,7 @@
 #include "http2.h"
 #include "setopt.h"
 #include "multiif.h"
+#include "altsvc.h"
 
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
@@ -2655,6 +2656,31 @@ static CURLcode vsetopt(struct Curl_easy *data, CURLoption option,
     data->set.trailer_data = va_arg(param, void *);
 #endif
     break;
+#ifdef USE_ALTSVC
+  case CURLOPT_ALTSVC:
+    if(!data->asi) {
+      data->asi = Curl_altsvc_init();
+      if(!data->asi)
+        return CURLE_OUT_OF_MEMORY;
+    }
+    argptr = va_arg(param, char *);
+    result = Curl_setstropt(&data->set.str[STRING_ALTSVC], argptr);
+    if(result)
+      return result;
+    (void)Curl_altsvc_load(data->asi, argptr);
+    break;
+  case CURLOPT_ALTSVC_CTRL:
+    if(!data->asi) {
+      data->asi = Curl_altsvc_init();
+      if(!data->asi)
+        return CURLE_OUT_OF_MEMORY;
+    }
+    arg = va_arg(param, long);
+    result = Curl_altsvc_ctrl(data->asi, arg);
+    if(result)
+      return result;
+    break;
+#endif
   default:
     /* unknown tag and its companion, just ignore: */
     result = CURLE_UNKNOWN_OPTION;
diff --git a/lib/url.c b/lib/url.c
index 3b4ff3ee7..bc00bfae6 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -120,6 +120,7 @@ bool curl_win32_idn_to_ascii(const char *in, char **out);
 #include "dotdot.h"
 #include "strdup.h"
 #include "setopt.h"
+#include "altsvc.h"
 
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
@@ -374,6 +375,11 @@ CURLcode Curl_close(struct Curl_easy *data)
   Curl_safefree(data->state.headerbuff);
   Curl_safefree(data->state.ulbuf);
   Curl_flush_cookies(data, 1);
+#ifdef USE_ALTSVC
+  Curl_altsvc_save(data->asi, data->set.str[STRING_ALTSVC]);
+  Curl_altsvc_cleanup(data->asi);
+  data->asi = NULL;
+#endif
   Curl_digest_cleanup(data);
   Curl_safefree(data->info.contenttype);
   Curl_safefree(data->info.wouldredirect);
@@ -3368,6 +3374,34 @@ static CURLcode parse_connect_to_slist(struct Curl_easy *data,
     conn_to_host = conn_to_host->next;
   }
 
+#ifdef USE_ALTSVC
+  if(data->asi && !host && (port == -1) &&
+     (conn->handler->protocol == CURLPROTO_HTTPS)) {
+    /* no connect_to match, try alt-svc! */
+    const char *nhost;
+    int nport;
+    enum alpnid nalpnid;
+    bool hit;
+    host = conn->host.rawalloc;
+    hit = Curl_altsvc_lookup(data->asi,
+                             ALPN_h1, host, conn->remote_port, /* from */
+                             &nalpnid, &nhost, &nport /* to */);
+    if(hit) {
+      char *hostd = strdup((char *)nhost);
+      if(!hostd)
+        return CURLE_OUT_OF_MEMORY;
+      conn->conn_to_host.rawalloc = hostd;
+      conn->conn_to_host.name = hostd;
+      conn->bits.conn_to_host = TRUE;
+      conn->conn_to_port = nport;
+      conn->bits.conn_to_port = TRUE;
+      infof(data, "Alt-svc connecting from [%s]%s:%d to [%s]%s:%d\n",
+            Curl_alpnid2str(ALPN_h1), host, conn->remote_port,
+            Curl_alpnid2str(nalpnid), hostd, nport);
+    }
+  }
+#endif
+
   return result;
 }
 
diff --git a/lib/urldata.h b/lib/urldata.h
index f3b8d3373..e5596b87f 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -1478,6 +1478,9 @@ enum dupstring {
 #endif
   STRING_TARGET,                /* CURLOPT_REQUEST_TARGET */
   STRING_DOH,                   /* CURLOPT_DOH_URL */
+#ifdef USE_ALTSVC
+  STRING_ALTSVC,                /* CURLOPT_ALTSVC */
+#endif
   /* -- end of zero-terminated strings -- */
 
   STRING_LASTZEROTERMINATED,
@@ -1794,6 +1797,9 @@ struct Curl_easy {
                                   NOTE that the 'cookie' field in the
                                   UserDefined struct defines if the "engine"
                                   is to be used or not. */
+#ifdef USE_ALTSVC
+  struct altsvcinfo *asi;      /* the alt-svc cache */
+#endif
   struct Progress progress;    /* for all the progress meter data */
   struct UrlState state;       /* struct for fields used for state info and
                                   other dynamic purposes */
diff --git a/lib/version.c b/lib/version.c
index c1be9ab6d..9369ae8e3 100644
--- a/lib/version.c
+++ b/lib/version.c
@@ -370,6 +370,9 @@ static curl_version_info_data version_info = {
 #if defined(HAVE_BROTLI)
   | CURL_VERSION_BROTLI
 #endif
+#if defined(USE_ALTSVC)
+  | CURL_VERSION_ALTSVC
+#endif
   ,
   NULL, /* ssl_version */
   0,    /* ssl_version_num, this is kept at zero */