upstream/mercurial-mirror Files · mercurial/mpatch.h

httppeer: remove support for connecting to <0.9.1 servers (BC)...

httppeer: remove support for connecting to <0.9.1 servers (BC) Previously, HTTP wire protocol clients would attempt a "capabilities" wire protocol command. If that failed, they would fall back to issuing a "between" command. The "capabilities" command was added in Mercurial 0.9.1 (released July 2006). The "between" command has been present for as long as the wire protocol has existed. So if the "between" command failed, it was safe to assume that the remote could not speak any version of the Mercurial wire protocol. The "between" fallback was added in in 2011. Before that changeset, Mercurial would *always* issue the "between" command and would issue "capabilities" if capabilities were requested. At that time, many connections would issue "capabilities" eventually, so it was decided to issue "capabilities" by default and fall back to "between" if that failed. This saved a round trip when connecting to modern servers while still preserving compatibility with legacy servers. Fast forward ~7 years. Mercurial servers supporting "capabilities" have been around for over a decade. If modern clients are connecting to <0.9.1 servers, they are getting a bad experience. They may even be getting bad data (an old server is vulnerable to numerous security issues and could have been p0wned, leading to a Mercurial repository serving backdoors or other badness). In addition, the fallback can harm experience for modern servers. If a client experiences an intermittent HTTP request failure (due to bad network, etc) and falls back to a "between" that works, it would assume an empty capability set and would attempt to communicate with the repository using a very ancient wire protocol. Auditing HTTP logs for hg.mozilla.org, I did find a handful of requests for the null range of the "between" command. However, requests can be days apart. And when I do see requests, they come in batches. Those batches seem to correlate to spikes of HTTP 500 or other server/network events. So I think these requests are fallbacks from failed "capabilities" requests and not from old clients. If you need even more evidence to discontinue support, apparently we have no test coverage for communicating with servers not supporting "capabilities." I know this because all tests pass with the "between" fallback removed. Finally, server-side support for <0.9.1 pushing (the "addchangegroup" wire protocol command along with locking-related commands) was dropped from the HTTP client in in 2017 and the SSH client in in 2015. I think this all adds up to enough justification for removing client support for communicating with servers not supporting "capabilities." So this commit removes that fallback. Differential Revision: https://phab.mercurial-scm.org/D2001

Augie Fackler - - Load All Authors

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      #ifndef _HG_MPATCH_H_

      #define _HG_MPATCH_H_

      #define MPATCH_ERR_NO_MEM -3

      #define MPATCH_ERR_CANNOT_BE_DECODED -2

      #define MPATCH_ERR_INVALID_PATCH -1

      struct mpatch_frag {

      	int start, end, len;

      	const char *data;

      };

      struct mpatch_flist {

      	struct mpatch_frag *base, *head, *tail;

      };

      int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res);

      ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l);

      void mpatch_lfree(struct mpatch_flist *a);

      int mpatch_apply(char *buf, const char *orig, ssize_t len,

                       struct mpatch_flist *l);

      struct mpatch_flist *

      mpatch_fold(void *bins, struct mpatch_flist *(*get_next_item)(void *, ssize_t),

                  ssize_t start, ssize_t end);

      #endif

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				#ifndef _HG_MPATCH_H_
				#define _HG_MPATCH_H_

				#define MPATCH_ERR_NO_MEM -3
				#define MPATCH_ERR_CANNOT_BE_DECODED -2
				#define MPATCH_ERR_INVALID_PATCH -1

				struct mpatch_frag {
				int start, end, len;
				const char *data;
				};

				struct mpatch_flist {
				struct mpatch_frag base, head, *tail;
				};

				int mpatch_decode(const char bin, ssize_t len, struct mpatch_flist *res);
				ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l);
				void mpatch_lfree(struct mpatch_flist *a);
				int mpatch_apply(char buf, const char orig, ssize_t len,
				struct mpatch_flist *l);
				struct mpatch_flist *
				mpatch_fold(void bins, struct mpatch_flist (get_next_item)(void , ssize_t),
				ssize_t start, ssize_t end);

				#endif