On 11/20, Jonathan Nieder wrote: > Android's "repo" tool is a tool for managing a large codebase > consisting of multiple smaller repositories, similar to Git's > submodule feature. Starting with Git 94b8ae5a (ssh: introduce a > 'simple' ssh variant, 2017-10-16), users noticed that it stopped > handling the port in ssh:// URLs. > > The cause: when it encounters ssh:// URLs, repo pre-connects to the > server and sets GIT_SSH to a helper ".repo/repo/git_ssh" that reuses > that connection. Before 94b8ae5a, the helper was assumed to support > OpenSSH options for lack of a better guess and got passed a -p option > to set the port. After that patch, it uses the new default of a > simple helper that does not accept an option to set the port. > > The next release of "repo" will set GIT_SSH_VARIANT to "ssh" to avoid > that. But users of old versions and of other similar GIT_SSH > implementations would not get the benefit of that fix. > > So update the default to use OpenSSH options again, with a twist. As > observed in 94b8ae5a, we cannot assume that $GIT_SSH always handles > OpenSSH options: common helpers such as travis-ci's dpl[*] are > configured using GIT_SSH and do not accept OpenSSH options. So make > the default a new variant "auto", with the following behavior: > > 1. First, check for a recognized basename, like today. > > 2. If the basename is not recognized, check whether $GIT_SSH supports > OpenSSH options by running > > $GIT_SSH -G <options> <host> > > This returns status 0 and prints configuration in OpenSSH if it > recognizes all <options> and returns status 255 if it encounters > an unrecognized option. A wrapper script like > > exec ssh -- "$@" > > would fail with > > ssh: Could not resolve hostname -g: Name or service not known > > , correctly reflecting that it does not support OpenSSH options. > The command is run with stdin, stdout, and stderr redirected to > /dev/null so even a command that expects a terminal would exit > immediately. > > 3. Based on the result from step (2), behave like "ssh" (if it > succeeded) or "simple" (if it failed). > > This way, the default ssh variant for unrecognized commands can handle > both the repo and dpl cases as intended. > > This autodetection has been running on Google workstations since > 2017-10-23 with no reported negative effects. > > [*] https://github.com/travis-ci/dpl/blob/6c3fddfda1f2a85944c544446b068bac0a77c049/lib/dpl/provider.rb#L215 > > Reported-by: William Yan <wyan@xxxxxxxxxx> > Improved-by: Jonathan Tan <jonathantanmy@xxxxxxxxxx> > Signed-off-by: Jonathan Nieder <jrnieder@xxxxxxxxx> > --- > Added two notes to the commit message: > - describing the real-world testing this patch has undergone > - stdin, stdout, and stderr go to /dev/null, preventing a > hypothetical ssh variant that *ignores* -G from hanging waiting for > input from the terminal. > > This is to address the worries at > https://public-inbox.org/git/xmqq60b59toe.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxx/ > and https://public-inbox.org/git/CAGZ79kZTjUvcq_hKHCqTDoaBxt2x+9XcqYc6ao1bhcET2SM-PQ@xxxxxxxxxxxxxx/ > about hanging. > > No change to the code from last time. > Thanks a lot for getting this patch out. It's a much more robust solution than I had originally and should hopefully avoid any more issues with detecting different ssh programs. My only concern is there may be some program out there that uses -G in a way different from OpenSSH. Though realistically i don't think that is an issue because if that ends up being a problem we can just have the authors of the offending ssh client send a patch to us to fix it! :) > Documentation/config.txt | 24 +++++++++++++++--------- > connect.c | 32 +++++++++++++++++++++++++------- > t/t5601-clone.sh | 21 +++++++++++++++++++++ > 3 files changed, 61 insertions(+), 16 deletions(-) > > diff --git a/Documentation/config.txt b/Documentation/config.txt > index 0460af37e2..0c371ad786 100644 > --- a/Documentation/config.txt > +++ b/Documentation/config.txt > @@ -2081,16 +2081,22 @@ matched against are those given directly to Git commands. This means any URLs > visited as a result of a redirection do not participate in matching. > > ssh.variant:: > - Depending on the value of the environment variables `GIT_SSH` or > - `GIT_SSH_COMMAND`, or the config setting `core.sshCommand`, Git > - auto-detects whether to adjust its command-line parameters for use > - with ssh (OpenSSH), plink or tortoiseplink, as opposed to the default > - (simple). > + By default, Git determines the command line arguments to use > + based on the basename of the configured SSH command (configured > + using the environment variable `GIT_SSH` or `GIT_SSH_COMMAND` or > + the config setting `core.sshCommand`). If the basename is > + unrecognized, Git will attempt to detect support of OpenSSH > + options by first invoking the configured SSH command with the > + `-G` (print configuration) option and will subsequently use > + OpenSSH options (if that is successful) or no options besides > + the host and remote command (if it fails). > + > -The config variable `ssh.variant` can be set to override this auto-detection; > -valid values are `ssh`, `simple`, `plink`, `putty` or `tortoiseplink`. Any > -other value will be treated as normal ssh. This setting can be overridden via > -the environment variable `GIT_SSH_VARIANT`. > +The config variable `ssh.variant` can be set to override this detection. > +Valid values are `ssh` (to use OpenSSH options), `plink`, `putty`, > +`tortoiseplink`, `simple` (no options except the host and remote command). > +The default auto-detection can be explicitly requested using the value > +`auto`. Any other value is treated as `ssh`. This setting can also be > +overridden via the environment variable `GIT_SSH_VARIANT`. > + > The current command-line parameters used for each variant are as > follows: > diff --git a/connect.c b/connect.c > index d2fbb15cc5..455c54a2ec 100644 > --- a/connect.c > +++ b/connect.c > @@ -788,6 +788,7 @@ static const char *get_ssh_command(void) > } > > enum ssh_variant { > + VARIANT_AUTO, > VARIANT_SIMPLE, > VARIANT_SSH, > VARIANT_PLINK, > @@ -795,14 +796,16 @@ enum ssh_variant { > VARIANT_TORTOISEPLINK, > }; > > -static int override_ssh_variant(enum ssh_variant *ssh_variant) > +static void override_ssh_variant(enum ssh_variant *ssh_variant) > { > const char *variant = getenv("GIT_SSH_VARIANT"); > > if (!variant && git_config_get_string_const("ssh.variant", &variant)) > - return 0; > + return; > > - if (!strcmp(variant, "plink")) > + if (!strcmp(variant, "auto")) > + *ssh_variant = VARIANT_AUTO; > + else if (!strcmp(variant, "plink")) > *ssh_variant = VARIANT_PLINK; > else if (!strcmp(variant, "putty")) > *ssh_variant = VARIANT_PUTTY; > @@ -812,18 +815,18 @@ static int override_ssh_variant(enum ssh_variant *ssh_variant) > *ssh_variant = VARIANT_SIMPLE; > else > *ssh_variant = VARIANT_SSH; > - > - return 1; > } > > static enum ssh_variant determine_ssh_variant(const char *ssh_command, > int is_cmdline) > { > - enum ssh_variant ssh_variant = VARIANT_SIMPLE; > + enum ssh_variant ssh_variant = VARIANT_AUTO; > const char *variant; > char *p = NULL; > > - if (override_ssh_variant(&ssh_variant)) > + override_ssh_variant(&ssh_variant); > + > + if (ssh_variant != VARIANT_AUTO) > return ssh_variant; > > if (!is_cmdline) { > @@ -982,6 +985,21 @@ static void fill_ssh_args(struct child_process *conn, const char *ssh_host, > variant = determine_ssh_variant(ssh, 0); > } > > + if (variant == VARIANT_AUTO) { > + struct child_process detect = CHILD_PROCESS_INIT; > + > + detect.use_shell = conn->use_shell; > + detect.no_stdin = detect.no_stdout = detect.no_stderr = 1; > + > + argv_array_push(&detect.args, ssh); > + argv_array_push(&detect.args, "-G"); > + push_ssh_options(&detect.args, &detect.env_array, > + VARIANT_SSH, port, flags); > + argv_array_push(&detect.args, ssh_host); > + > + variant = run_command(&detect) ? VARIANT_SIMPLE : VARIANT_SSH; > + } > + > argv_array_push(&conn->args, ssh); > push_ssh_options(&conn->args, &conn->env_array, variant, port, flags); > argv_array_push(&conn->args, ssh_host); > diff --git a/t/t5601-clone.sh b/t/t5601-clone.sh > index 9d007c0f8d..209e2d5604 100755 > --- a/t/t5601-clone.sh > +++ b/t/t5601-clone.sh > @@ -369,6 +369,12 @@ test_expect_success 'variant can be overriden' ' > expect_ssh myhost src > ' > > +test_expect_success 'variant=auto picks based on basename' ' > + copy_ssh_wrapper_as "$TRASH_DIRECTORY/plink" && > + git -c ssh.variant=auto clone -4 "[myhost:123]:src" ssh-auto-clone && > + expect_ssh "-4 -P 123" myhost src > +' > + > test_expect_success 'simple is treated as simple' ' > copy_ssh_wrapper_as "$TRASH_DIRECTORY/simple" && > git clone -4 "[myhost:123]:src" ssh-bracket-clone-simple && > @@ -381,6 +387,21 @@ test_expect_success 'uplink is treated as simple' ' > expect_ssh myhost src > ' > > +test_expect_success 'OpenSSH-like uplink is treated as ssh' ' > + write_script "$TRASH_DIRECTORY/uplink" <<-EOF && > + if test "\$1" = "-G" > + then > + exit 0 > + fi && > + exec "\$TRASH_DIRECTORY/ssh$X" "\$@" > + EOF > + test_when_finished "rm -f \"\$TRASH_DIRECTORY/uplink\"" && > + GIT_SSH="$TRASH_DIRECTORY/uplink" && > + test_when_finished "GIT_SSH=\"\$TRASH_DIRECTORY/ssh\$X\"" && > + git clone "[myhost:123]:src" ssh-bracket-clone-sshlike-uplink && > + expect_ssh "-p 123" myhost src > +' > + > test_expect_success 'plink is treated specially (as putty)' ' > copy_ssh_wrapper_as "$TRASH_DIRECTORY/plink" && > git clone "[myhost:123]:src" ssh-bracket-clone-plink-0 && > -- > 2.15.0.448.gf294e3d99a > -- Brandon Williams
