diff mbox series

[4/5] http: centralize the accounting of libcurl dependencies

Message ID patch-4.5-47b513a261b-20210908T152807Z-avarab@gmail.com (mailing list archive)
State Superseded
Headers show
Series post-v2.33 "drop support for ancient curl" follow-up | expand

Commit Message

Ævar Arnfjörð Bjarmason Sept. 8, 2021, 3:31 p.m. UTC 
As discussed in 644de29e220 (http: drop support for curl < 7.19.4,
2021-07-30) checking against LIBCURL_VERSION_NUM isn't as reliable as
checking specific defines in curl, as some distros have been known to
backport features. Furthermore as shown in the preceding commit doing
these version checks makes for hard to read and possibly buggy code,
as shown by the bug fixed there where we were conflating base 10 for
base 16 when comparing the version.

Let's instead add a new git-curl-compat.h header that'll keep track of
these dependencies. Following this pattern will also make it much
easier to track when we should deprecate curl versions in the future,
as we just did post-v2.33 e48a623dea0 (Merge branch
'ab/http-drop-old-curl', 2021-08-24).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 git-curl-compat.h | 112 ++++++++++++++++++++++++++++++++++++++++++++++
 http.c            |  31 +++++++------
 imap-send.c       |   2 +-
 3 files changed, 128 insertions(+), 17 deletions(-)
 create mode 100644 git-curl-compat.h

Comments

Jeff King Sept. 8, 2021, 7:31 p.m. UTC | #1 
On Wed, Sep 08, 2021 at 05:31:55PM +0200, Ævar Arnfjörð Bjarmason wrote:

> As discussed in 644de29e220 (http: drop support for curl < 7.19.4,
> 2021-07-30) checking against LIBCURL_VERSION_NUM isn't as reliable as
> checking specific defines in curl, as some distros have been known to
> backport features. Furthermore as shown in the preceding commit doing
> these version checks makes for hard to read and possibly buggy code,
> as shown by the bug fixed there where we were conflating base 10 for
> base 16 when comparing the version.

Just playing devil's advocate for a moment: we are making the assumption
here that curl will use preprocessor macros to implement these constants
(as opposed to, say, enums). I think that has been historically true,
but it is an extra dependency we're adding on curl's internal-ish
details.

> +/**
> + * CURLOPT_TCP_KEEPALIVE was added in 7.25.0, released in March 2012.
> + */
> +#ifdef CURLOPT_TCP_KEEPALIVE
> +#define GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE 1
> +#endif
>
> [...]
>
> -#if LIBCURL_VERSION_NUM >= 0x071900
> +#ifdef GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE
>  static void set_curl_keepalive(CURL *c)
>  {
>  	curl_easy_setopt(c, CURLOPT_TCP_KEEPALIVE, 1);

Part of me is a little sad at the duplication this creates. We could
just be checking

  #ifdef CURLOPT_TCP_KEEPALIVE

in the second hunk, without the first one at all. That does make it
harder to see which ones are in use (and we'd still want a comment to
take note of the versions). I dunno. I guess having a central-ish
registry of these is worth the duplication.

-Peff
Junio C Hamano Sept. 9, 2021, 5:40 p.m. UTC | #2 
Jeff King <peff@peff.net> writes:

>> +/**
>> + * CURLOPT_TCP_KEEPALIVE was added in 7.25.0, released in March 2012.
>> + */
>> +#ifdef CURLOPT_TCP_KEEPALIVE
>> +#define GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE 1
>> +#endif
>>
>> [...]
>>
>> -#if LIBCURL_VERSION_NUM >= 0x071900
>> +#ifdef GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE
>>  static void set_curl_keepalive(CURL *c)
>>  {
>>  	curl_easy_setopt(c, CURLOPT_TCP_KEEPALIVE, 1);
>
> Part of me is a little sad at the duplication this creates. We could
> just be checking
>
>   #ifdef CURLOPT_TCP_KEEPALIVE
>
> in the second hunk, without the first one at all.

I recall having exactly the same reaction when the above pattern
first was floated.  

I still do not see how the GITCURL_* duplication is worth it.  What
do we want to gain from having a "central registry"?

If it is to see which ones we care about, would it be sufficient to
use the hits from "git grep -e CURL" with postprocessing?

Thanks.
Jeff King Sept. 9, 2021, 7:26 p.m. UTC | #3 
On Thu, Sep 09, 2021 at 10:40:44AM -0700, Junio C Hamano wrote:

> > Part of me is a little sad at the duplication this creates. We could
> > just be checking
> >
> >   #ifdef CURLOPT_TCP_KEEPALIVE
> >
> > in the second hunk, without the first one at all.
> 
> I recall having exactly the same reaction when the above pattern
> first was floated.  
> 
> I still do not see how the GITCURL_* duplication is worth it.  What
> do we want to gain from having a "central registry"?
> 
> If it is to see which ones we care about, would it be sufficient to
> use the hits from "git grep -e CURL" with postprocessing?

Just brain-storming:

  - It's probably a little easier to read, with the comments all
    together with the definitions (keeping in mind that some of these
    flags may need to be checked in several spots).

  - Likewise a few of the checks are non-trivial, with multiple ANDs, so
    it may be nicer to have a single registry (though the resulting
    "GIT_CURL_HAVE_X_and_Y_and_Z" are pretty ugly to me).

  - _Possibly_ it provides a knob for the user to say
    "-DGIT_CURL_HAVE_FOO=1" by overriding our auto-detection. But since
    most of these are "do we have FOO defined? Because are about to
    reference it in the code", I don't see what that override would buy
    you.

I dunno. I admit that I do not overly care that much. Handling curl
version dependencies was neglected for many years. If Ævar wants to take
a more active role in handling these and this is convenient for him, I'm
happy enough however it works.

-Peff
diff mbox series

Patch

diff --git a/git-curl-compat.h b/git-curl-compat.h
new file mode 100644
index 00000000000..2bba7adefa6
--- /dev/null
+++ b/git-curl-compat.h
@@ -0,0 +1,112 @@ 
+#ifndef GIT_CURL_COMPAT_H
+#define GIT_CURL_COMPAT_H
+
+/**
+ * This header centralizes the declaration of our libcurl dependencies
+ * to make it easy to discover the oldest versions we support, and to
+ * inform decisions about removing support for older libcurl in the
+ * future.
+ *
+ * The source of truth for what versions have which symbols is
+ * https://github.com/curl/curl/blob/master/docs/libcurl/symbols-in-versions;
+ * the release dates are taken from curl.git (at
+ * https://github.com/curl/curl/).
+ *
+ * For each X symbol we need from curl we check if it exists and
+ * declare our own GIT_CURL_HAVE_X, or if it's for both X and Y
+ * GIT_CURL_HAVE_X_and_Y, where the "Y" in "X_and_Y" is only the part
+ * of the symbol name that "X" and "Y" don't have in common.
+ *
+ * We avoid comparisons against LIBCURL_VERSION_NUM, enterprise
+ * distros have been known to backport symbols to their older curl
+ * versions.
+ *
+ * Keep any symbols in date order of when their support was
+ * introduced, oldest first, in the official version of cURL library.
+ */
+
+/**
+ * CURLOPT_TCP_KEEPALIVE was added in 7.25.0, released in March 2012.
+ */
+#ifdef CURLOPT_TCP_KEEPALIVE
+#define GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE 1
+#endif
+
+
+/**
+ * CURLOPT_LOGIN_OPTIONS was added in 7.34.0, released in December
+ * 2013.
+ */
+#ifdef CURLOPT_LOGIN_OPTIONS
+#define GIT_CURL_HAVE_CURLOPT_LOGIN_OPTIONS 1
+#endif
+
+/**
+ * CURL_SSLVERSION_TLSv1_[012] was added in 7.34.0, released in
+ * December 2013.
+ */
+#if defined(CURL_SSLVERSION_TLSv1_0) && \
+    defined(CURL_SSLVERSION_TLSv1_1) && \
+    defined(CURL_SSLVERSION_TLSv1_2)
+#define GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_0_and_1_and_2
+#endif
+
+/**
+ * CURLOPT_PINNEDPUBLICKEY was added in 7.39.0, released in November
+ * 2014.
+ */
+#ifdef CURLOPT_PINNEDPUBLICKEY
+#define GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY 1
+#endif
+
+/**
+ * CURL_HTTP_VERSION_2 was added in 7.43.0, released in June 2015.
+ */
+#ifdef CURL_HTTP_VERSION_2
+#define GIT_CURL_HAVE_CURL_HTTP_VERSION_2 1
+#endif
+
+/**
+ * CURLSSLOPT_NO_REVOKE was added in 7.44.0, released in August 2015.
+ */
+#ifdef CURLSSLOPT_NO_REVOKE
+#define GIT_CURL_HAVE_CURLSSLOPT_NO_REVOKE 1
+#endif
+
+/**
+ * CURLOPT_PROXY_CAINFO was added in 7.52.0, released in August 2017.
+ */
+#ifdef CURLOPT_PROXY_CAINFO
+#define GIT_CURL_HAVE_CURLOPT_PROXY_CAINFO 1
+#endif
+
+/**
+ * CURLOPT_PROXY_{KEYPASSWD,SSLCERT,SSLKEY} was added in 7.52.0,
+ * released in August 2017.
+ */
+#if defined(CURLOPT_PROXY_KEYPASSWD) && \
+    defined(CURLOPT_PROXY_SSLCERT) && \
+    defined(CURLOPT_PROXY_SSLKEY)
+#define GIT_CURL_HAVE_CURLOPT_PROXY_KEYPASSWD_and_SSLCERT_and_SSLKEY 1
+#endif
+
+/**
+ * CURL_SSLVERSION_TLSv1_3 was added in 7.53.0, released in February
+ * 2017.
+ */
+#ifdef CURL_SSLVERSION_TLSv1_3
+#define GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_3 1
+#endif
+
+/**
+ * CURLSSLSET_{NO_BACKENDS,OK,TOO_LATE,UNKNOWN_BACKEND} were added in
+ * 7.56.0, released in September 2017.
+ */
+#if defined(CURLSSLSET_NO_BACKENDS) && \
+    defined(CURLSSLSET_OK) && \
+    defined(CURLSSLSET_TOO_LATE) && \
+    defined(CURLSSLSET_UNKNOWN_BACKEND)
+#define GIT_CURL_HAVE_CURLSSLSET_NO_BACKENDS_and_OK_and_TOO_LATE_and_UNKNOWN_BACKEND 1
+#endif
+
+#endif
diff --git a/http.c b/http.c
index b19d0a697d8..e38fcc34d64 100644
--- a/http.c
+++ b/http.c
@@ -1,4 +1,5 @@ 
 #include "git-compat-util.h"
+#include "git-curl-compat.h"
 #include "http.h"
 #include "config.h"
 #include "pack.h"
@@ -47,12 +48,12 @@  static struct {
 	{ "sslv2", CURL_SSLVERSION_SSLv2 },
 	{ "sslv3", CURL_SSLVERSION_SSLv3 },
 	{ "tlsv1", CURL_SSLVERSION_TLSv1 },
-#if LIBCURL_VERSION_NUM >= 0x072200
+#if GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_0_AND_1_AND_2
 	{ "tlsv1.0", CURL_SSLVERSION_TLSv1_0 },
 	{ "tlsv1.1", CURL_SSLVERSION_TLSv1_1 },
 	{ "tlsv1.2", CURL_SSLVERSION_TLSv1_2 },
 #endif
-#if LIBCURL_VERSION_NUM >= 0x073400
+#if GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_3
 	{ "tlsv1.3", CURL_SSLVERSION_TLSv1_3 },
 #endif
 };
@@ -371,12 +372,10 @@  static int http_options(const char *var, const char *value, void *cb)
 	}
 
 	if (!strcmp("http.pinnedpubkey", var)) {
-#if LIBCURL_VERSION_NUM >= 0x072700
-		return git_config_pathname(&ssl_pinnedkey, var, value);
-#else
+#ifndef GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY
 		warning(_("Public key pinning not supported with cURL < 7.39.0"));
-		return 0;
 #endif
+		return git_config_pathname(&ssl_pinnedkey, var, value);
 	}
 
 	if (!strcmp("http.extraheader", var)) {
@@ -498,7 +497,7 @@  static int has_cert_password(void)
 	return 1;
 }
 
-#if LIBCURL_VERSION_NUM >= 0x073400
+#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_KEYPASSWD_and_SSLCERT_and_SSLKEY
 static int has_proxy_cert_password(void)
 {
 	if (http_proxy_ssl_cert == NULL || proxy_ssl_cert_password_required != 1)
@@ -514,7 +513,7 @@  static int has_proxy_cert_password(void)
 }
 #endif
 
-#if LIBCURL_VERSION_NUM >= 0x071900
+#ifdef GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE
 static void set_curl_keepalive(CURL *c)
 {
 	curl_easy_setopt(c, CURLOPT_TCP_KEEPALIVE, 1);
@@ -730,7 +729,7 @@  static long get_curl_allowed_protocols(int from_user)
 	return allowed_protocols;
 }
 
-#if LIBCURL_VERSION_NUM >=0x072b00
+#ifdef GIT_CURL_HAVE_CURL_HTTP_VERSION_2
 static int get_curl_http_version_opt(const char *version_string, long *opt)
 {
 	int i;
@@ -772,7 +771,7 @@  static CURL *get_curl_handle(void)
 		curl_easy_setopt(result, CURLOPT_SSL_VERIFYHOST, 2);
 	}
 
-#if LIBCURL_VERSION_NUM >= 0x072b00
+#ifdef GIT_CURL_HAVE_CURL_HTTP_VERSION_2
     if (curl_http_version) {
 		long opt;
 		if (!get_curl_http_version_opt(curl_http_version, &opt)) {
@@ -803,7 +802,7 @@  static CURL *get_curl_handle(void)
 
 	if (http_ssl_backend && !strcmp("schannel", http_ssl_backend) &&
 	    !http_schannel_check_revoke) {
-#if LIBCURL_VERSION_NUM >= 0x072c00
+#ifdef GIT_CURL_HAVE_CURLSSLOPT_NO_REVOKE
 		curl_easy_setopt(result, CURLOPT_SSL_OPTIONS, CURLSSLOPT_NO_REVOKE);
 #else
 		warning(_("CURLSSLOPT_NO_REVOKE not supported with cURL < 7.44.0"));
@@ -843,20 +842,20 @@  static CURL *get_curl_handle(void)
 		curl_easy_setopt(result, CURLOPT_SSLKEY, ssl_key);
 	if (ssl_capath != NULL)
 		curl_easy_setopt(result, CURLOPT_CAPATH, ssl_capath);
-#if LIBCURL_VERSION_NUM >= 0x072700
+#ifdef GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY
 	if (ssl_pinnedkey != NULL)
 		curl_easy_setopt(result, CURLOPT_PINNEDPUBLICKEY, ssl_pinnedkey);
 #endif
 	if (http_ssl_backend && !strcmp("schannel", http_ssl_backend) &&
 	    !http_schannel_use_ssl_cainfo) {
 		curl_easy_setopt(result, CURLOPT_CAINFO, NULL);
-#if LIBCURL_VERSION_NUM >= 0x073400
+#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_CAINFO
 		curl_easy_setopt(result, CURLOPT_PROXY_CAINFO, NULL);
 #endif
 	} else if (ssl_cainfo != NULL || http_proxy_ssl_ca_info != NULL) {
 		if (ssl_cainfo != NULL)
 			curl_easy_setopt(result, CURLOPT_CAINFO, ssl_cainfo);
-#if LIBCURL_VERSION_NUM >= 0x073400
+#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_CAINFO
 		if (http_proxy_ssl_ca_info != NULL)
 			curl_easy_setopt(result, CURLOPT_PROXY_CAINFO, http_proxy_ssl_ca_info);
 #endif
@@ -937,7 +936,7 @@  static CURL *get_curl_handle(void)
 		else if (starts_with(curl_http_proxy, "socks"))
 			curl_easy_setopt(result,
 				CURLOPT_PROXYTYPE, CURLPROXY_SOCKS4);
-#if LIBCURL_VERSION_NUM >= 0x073400
+#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_KEYPASSWD_and_SSLCERT_and_SSLKEY
 		else if (starts_with(curl_http_proxy, "https")) {
 			curl_easy_setopt(result, CURLOPT_PROXYTYPE, CURLPROXY_HTTPS);
 
@@ -1002,7 +1001,7 @@  void http_init(struct remote *remote, const char *url, int proactive_auth)
 	free(normalized_url);
 	string_list_clear(&config.vars, 1);
 
-#if LIBCURL_VERSION_NUM >= 0x073800
+#ifdef GIT_CURL_HAVE_CURLSSLSET_NO_BACKENDS_and_OK_and_TOO_LATE_and_UNKNOWN_BACKEND
 	if (http_ssl_backend) {
 		const curl_ssl_backend **backends;
 		struct strbuf buf = STRBUF_INIT;
diff --git a/imap-send.c b/imap-send.c
index 49a5f8aa597..e6090a0346a 100644
--- a/imap-send.c
+++ b/imap-send.c
@@ -1441,7 +1441,7 @@  static CURL *setup_curl(struct imap_server_conf *srvc, struct credential *cred)
 	curl_easy_setopt(curl, CURLOPT_PORT, server.port);
 
 	if (server.auth_method) {
-#if LIBCURL_VERSION_NUM < 0x072200
+#ifndef GIT_CURL_HAVE_CURLOPT_LOGIN_OPTIONS
 		warning("No LOGIN_OPTIONS support in this cURL version");
 #else
 		struct strbuf auth = STRBUF_INIT;