abuild: fix fetch lock file on nfs

flock(2) on an NFS mount will on the server side convert the lock to a
POSIX lock (fcntl(F_SETLK)). This means that abuild running on NFS
server and client will create different locks and they will both try
download same file at same time.

We fix this by creating a small abuild-fetch application that will
create a POSIX lock which works with NFS.

1 files changed, 194 insertions, 0 deletions

diff --git a/abuild-fetch.c b/abuild-fetch.c
new file mode 100644
index 0000000..51b41eb
--- /dev/null
+++ b/abuild-fetch.c
@@ -0,0 +1,194 @@
+/* MIT license
+
+Copyright (C) 2015 Natanael Copa <ncopa@alpinelinux.org>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
+*/
+
+
+#include <sys/wait.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static char *program;
+static char lockfile[PATH_MAX] = "";
+
+struct cmdarray {
+	size_t argc;
+	char *argv[32];
+};
+
+void add_opt(struct cmdarray *cmd, char *opt)
+{
+	cmd->argv[cmd->argc++] = opt;
+	cmd->argv[cmd->argc] = NULL;
+}
+
+int usage(int eval)
+{
+	printf("usage: %s [-d DESTDIR] URL\n", program);
+	return eval;
+}
+
+/* create or wait for an NFS-safe lockfile and fetch url with curl or wget */
+int fetch(char *url, const char *destdir)
+{
+	int lockfd, status=0;
+	pid_t childpid;
+	char outfile[PATH_MAX], partfile[PATH_MAX];
+	char *name, *p;
+	struct flock fl = {
+		.l_type = F_WRLCK,
+		.l_whence = SEEK_SET,
+		.l_start = 1,
+		.l_len = 0,
+	};
+	struct cmdarray curlcmd = {
+		.argc = 6,
+		.argv = { "curl", "-k", "-L", "-f", "-o", partfile, NULL }
+	};
+	struct cmdarray wgetcmd = {
+		.argc = 3,
+		.argv = { "wget", "-O", partfile, NULL }
+	};
+
+	name = strrchr(url, '/');
+	if (name == NULL)
+		errx(1, "%s: no '/' in url");
+	p = strstr(url, "::");
+	if (p != NULL) {
+		name = url;
+		*p = '\0';
+		url = p + 2;
+	} else if (strstr(url, "saveas-") == url) {
+		*name++ = '\0';
+		url += 7;  /* strlen("saveas-") */
+	} else {
+		name++;
+	}
+
+	snprintf(outfile, sizeof(outfile), "%s/%s", destdir, name);
+	snprintf(lockfile, sizeof(lockfile), "%s.lock", outfile);
+	snprintf(partfile, sizeof(partfile), "%s.part", outfile);
+
+	lockfd = open(lockfile, O_WRONLY|O_CREAT, 0660);
+	if (lockfd < 0)
+		err(1, lockfile);
+
+	if (fcntl(lockfd, F_SETLK, &fl) < 0) {
+		printf("Waiting for %s ...\n", lockfile);
+		if (fcntl(lockfd, F_SETLKW, &fl) < 0)
+			err(1, "fcntl(F_SETLKW)");
+	}
+
+	if (access(outfile, F_OK) == 0)
+		goto fetch_done;
+
+	if (access(partfile, F_OK) == 0) {
+		printf("Partial download found. Trying to resume.\n");
+		add_opt(&curlcmd, "-C");
+		add_opt(&curlcmd, "-");
+		add_opt(&wgetcmd, "-c");
+	}
+
+	add_opt(&curlcmd, url);
+	add_opt(&wgetcmd, url);
+
+	childpid = fork();
+	if (childpid < 0 )
+		err(1, "fork");
+
+	if (childpid == 0) {
+		execvp(curlcmd.argv[0], curlcmd.argv);
+		printf("Using wget\n");
+		execvp(wgetcmd.argv[0], wgetcmd.argv);
+		warn(wgetcmd.argv[0]);
+		unlink(lockfile);
+		exit(1);
+	}
+	wait(&status);
+	rename(partfile, outfile);
+
+fetch_done:
+	unlink(lockfile);
+	close(lockfd);
+	lockfile[0] = '\0';
+	return status;
+
+}
+
+void sighandler(int sig)
+{
+	switch(sig) {
+	case SIGABRT:
+	case SIGINT:
+	case SIGQUIT:
+	case SIGTERM:
+		unlink(lockfile);
+		exit(0);
+		break;
+	default:
+		break;
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	int opt, r=0, i;
+	char *destdir = "/var/cache/distfiles";
+
+	program = argv[0];
+	while ((opt = getopt(argc, argv, "hd:")) != -1) {
+		switch (opt) {
+		case 'h':
+			return usage(0);
+			break;
+		case 'd':
+			destdir = optarg;
+			break;
+		default:
+			printf("Unkonwn option '%c'\n", opt);
+			return usage(1);
+			break;
+		}
+	}
+
+	argv += optind;
+	argc -= optind;
+
+	if (argc < 1)
+		return usage(1);
+
+	signal(SIGABRT, sighandler);
+	signal(SIGINT, sighandler);
+	signal(SIGQUIT, sighandler);
+	signal(SIGTERM, sighandler);
+
+	for (i = 0; i < argc; i++) {
+		if (fetch(argv[i], destdir))
+			r++;
+	}
+	return r;
+}