git

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#include "git-compat-util.h"
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#include "abspath.h"
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#include "sigchain.h"
4
#include "strbuf.h"
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#include "trace2/tr2_dst.h"
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#include "trace2/tr2_sid.h"
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#include "trace2/tr2_sysenv.h"
8

9
/*
10
 * How many attempts we will make at creating an automatically-named trace file.
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 */
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#define MAX_AUTO_ATTEMPTS 10
13

14
/*
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 * Sentinel file used to detect when we should discard new traces to avoid
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 * writing too many trace files to a directory.
17
 */
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#define DISCARD_SENTINEL_NAME "git-trace2-discard"
19

20
/*
21
 * When set to zero, disables directory file count checks. Otherwise, controls
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 * how many files we can write to a directory before entering discard mode.
23
 * This can be overridden via the TR2_SYSENV_MAX_FILES setting.
24
 */
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static int tr2env_max_files = 0;
26

27
static int tr2_dst_want_warning(void)
28
{
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	static int tr2env_dst_debug = -1;
30

31
	if (tr2env_dst_debug == -1) {
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		const char *env_value = tr2_sysenv_get(TR2_SYSENV_DST_DEBUG);
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		if (!env_value || !*env_value)
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			tr2env_dst_debug = 0;
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		else
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			tr2env_dst_debug = atoi(env_value) > 0;
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	}
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	return tr2env_dst_debug;
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}
41

42
void tr2_dst_trace_disable(struct tr2_dst *dst)
43
{
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	if (dst->need_close)
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		close(dst->fd);
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	dst->fd = 0;
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	dst->initialized = 1;
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	dst->need_close = 0;
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}
50

51
/*
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 * Check to make sure we're not overloading the target directory with too many
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 * files. First get the threshold (if present) from the config or envvar. If
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 * it's zero or unset, disable this check. Next check for the presence of a
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 * sentinel file, then check file count.
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 *
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 * Returns 0 if tracing should proceed as normal. Returns 1 if the sentinel file
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 * already exists, which means tracing should be disabled. Returns -1 if there
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 * are too many files but there was no sentinel file, which means we have
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 * created and should write traces to the sentinel file.
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 *
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 * We expect that some trace processing system is gradually collecting files
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 * from the target directory; after it removes the sentinel file we'll start
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 * writing traces again.
65
 */
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static int tr2_dst_too_many_files(struct tr2_dst *dst, const char *tgt_prefix)
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{
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	int file_count = 0, max_files = 0, ret = 0;
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	const char *max_files_var;
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	DIR *dirp;
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	struct strbuf path = STRBUF_INIT, sentinel_path = STRBUF_INIT;
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	struct stat statbuf;
73

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	/* Get the config or envvar and decide if we should continue this check */
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	max_files_var = tr2_sysenv_get(TR2_SYSENV_MAX_FILES);
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	if (max_files_var && *max_files_var && ((max_files = atoi(max_files_var)) >= 0))
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		tr2env_max_files = max_files;
78

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	if (!tr2env_max_files) {
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		ret = 0;
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		goto cleanup;
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	}
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	strbuf_addstr(&path, tgt_prefix);
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	if (!is_dir_sep(path.buf[path.len - 1])) {
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		strbuf_addch(&path, '/');
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	}
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	/* check sentinel */
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	strbuf_addbuf(&sentinel_path, &path);
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	strbuf_addstr(&sentinel_path, DISCARD_SENTINEL_NAME);
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	if (!stat(sentinel_path.buf, &statbuf)) {
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		ret = 1;
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		goto cleanup;
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	}
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	/* check file count */
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	dirp = opendir(path.buf);
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	while (file_count < tr2env_max_files && dirp && readdir(dirp))
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		file_count++;
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	if (dirp)
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		closedir(dirp);
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	if (file_count >= tr2env_max_files) {
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		dst->too_many_files = 1;
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		dst->fd = open(sentinel_path.buf, O_WRONLY | O_CREAT | O_EXCL, 0666);
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		ret = -1;
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		goto cleanup;
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	}
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cleanup:
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	strbuf_release(&path);
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	strbuf_release(&sentinel_path);
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	return ret;
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}
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static int tr2_dst_try_auto_path(struct tr2_dst *dst, const char *tgt_prefix)
118
{
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	int too_many_files;
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	const char *last_slash, *sid = tr2_sid_get();
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	struct strbuf path = STRBUF_INIT;
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	size_t base_path_len;
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	unsigned attempt_count;
124

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	last_slash = strrchr(sid, '/');
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	if (last_slash)
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		sid = last_slash + 1;
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	strbuf_addstr(&path, tgt_prefix);
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	if (!is_dir_sep(path.buf[path.len - 1]))
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		strbuf_addch(&path, '/');
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	strbuf_addstr(&path, sid);
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	base_path_len = path.len;
134

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	too_many_files = tr2_dst_too_many_files(dst, tgt_prefix);
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	if (!too_many_files) {
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		for (attempt_count = 0; attempt_count < MAX_AUTO_ATTEMPTS; attempt_count++) {
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			if (attempt_count > 0) {
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				strbuf_setlen(&path, base_path_len);
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				strbuf_addf(&path, ".%d", attempt_count);
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			}
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			dst->fd = open(path.buf, O_WRONLY | O_CREAT | O_EXCL, 0666);
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			if (dst->fd != -1)
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				break;
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		}
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	} else if (too_many_files == 1) {
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		strbuf_release(&path);
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		if (tr2_dst_want_warning())
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			warning("trace2: not opening %s trace file due to too "
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				"many files in target directory %s",
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				tr2_sysenv_display_name(dst->sysenv_var),
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				tgt_prefix);
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		return 0;
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	}
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	if (dst->fd == -1) {
158
		if (tr2_dst_want_warning())
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			warning("trace2: could not open '%.*s' for '%s' tracing: %s",
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				(int) base_path_len, path.buf,
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				tr2_sysenv_display_name(dst->sysenv_var),
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				strerror(errno));
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164
		tr2_dst_trace_disable(dst);
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		strbuf_release(&path);
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		return 0;
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	}
168

169
	strbuf_release(&path);
170

171
	dst->need_close = 1;
172
	dst->initialized = 1;
173

174
	return dst->fd;
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}
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177
static int tr2_dst_try_path(struct tr2_dst *dst, const char *tgt_value)
178
{
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	int fd = open(tgt_value, O_WRONLY | O_APPEND | O_CREAT, 0666);
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	if (fd == -1) {
181
		if (tr2_dst_want_warning())
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			warning("trace2: could not open '%s' for '%s' tracing: %s",
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				tgt_value,
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				tr2_sysenv_display_name(dst->sysenv_var),
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				strerror(errno));
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187
		tr2_dst_trace_disable(dst);
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		return 0;
189
	}
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191
	dst->fd = fd;
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	dst->need_close = 1;
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	dst->initialized = 1;
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195
	return dst->fd;
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}
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#ifndef NO_UNIX_SOCKETS
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#define PREFIX_AF_UNIX "af_unix:"
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#define PREFIX_AF_UNIX_STREAM "af_unix:stream:"
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#define PREFIX_AF_UNIX_DGRAM "af_unix:dgram:"
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static int tr2_dst_try_uds_connect(const char *path, int sock_type, int *out_fd)
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{
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	int fd;
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	struct sockaddr_un sa;
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	fd = socket(AF_UNIX, sock_type, 0);
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	if (fd == -1)
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		return -1;
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212
	sa.sun_family = AF_UNIX;
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	strlcpy(sa.sun_path, path, sizeof(sa.sun_path));
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215
	if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
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		int saved_errno = errno;
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		close(fd);
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		errno = saved_errno;
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		return -1;
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	}
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	*out_fd = fd;
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	return 0;
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}
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#define TR2_DST_UDS_TRY_STREAM (1 << 0)
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#define TR2_DST_UDS_TRY_DGRAM  (1 << 1)
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static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
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					  const char *tgt_value)
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{
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	unsigned int uds_try = 0;
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	int fd;
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	const char *path = NULL;
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236
	/*
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	 * Allow "af_unix:[<type>:]<absolute_path>"
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	 *
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	 * Trace2 always writes complete individual messages (without
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	 * chunking), so we can talk to either DGRAM or STREAM type sockets.
241
	 *
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	 * Allow the user to explicitly request the socket type.
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	 *
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	 * If they omit the socket type, try one and then the other.
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	 */
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247
	if (skip_prefix(tgt_value, PREFIX_AF_UNIX_STREAM, &path))
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		uds_try |= TR2_DST_UDS_TRY_STREAM;
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250
	else if (skip_prefix(tgt_value, PREFIX_AF_UNIX_DGRAM, &path))
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		uds_try |= TR2_DST_UDS_TRY_DGRAM;
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	else if (skip_prefix(tgt_value, PREFIX_AF_UNIX, &path))
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		uds_try |= TR2_DST_UDS_TRY_STREAM | TR2_DST_UDS_TRY_DGRAM;
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	if (!path || !*path) {
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		if (tr2_dst_want_warning())
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			warning("trace2: invalid AF_UNIX value '%s' for '%s' tracing",
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				tgt_value,
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				tr2_sysenv_display_name(dst->sysenv_var));
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262
		tr2_dst_trace_disable(dst);
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		return 0;
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	}
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	if (!is_absolute_path(path) ||
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	    strlen(path) >= sizeof(((struct sockaddr_un *)0)->sun_path)) {
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		if (tr2_dst_want_warning())
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			warning("trace2: invalid AF_UNIX path '%s' for '%s' tracing",
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				path, tr2_sysenv_display_name(dst->sysenv_var));
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272
		tr2_dst_trace_disable(dst);
273
		return 0;
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	}
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	if (uds_try & TR2_DST_UDS_TRY_STREAM) {
277
		if (!tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd))
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			goto connected;
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		if (errno != EPROTOTYPE)
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			goto error;
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	}
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	if (uds_try & TR2_DST_UDS_TRY_DGRAM) {
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		if (!tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd))
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			goto connected;
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	}
286

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error:
288
	if (tr2_dst_want_warning())
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		warning("trace2: could not connect to socket '%s' for '%s' tracing: %s",
290
			path, tr2_sysenv_display_name(dst->sysenv_var),
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			strerror(errno));
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293
	tr2_dst_trace_disable(dst);
294
	return 0;
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296
connected:
297
	dst->fd = fd;
298
	dst->need_close = 1;
299
	dst->initialized = 1;
300

301
	return dst->fd;
302
}
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#endif
304

305
static void tr2_dst_malformed_warning(struct tr2_dst *dst,
306
				      const char *tgt_value)
307
{
308
	warning("trace2: unknown value for '%s': '%s'",
309
		tr2_sysenv_display_name(dst->sysenv_var), tgt_value);
310
}
311

312
int tr2_dst_get_trace_fd(struct tr2_dst *dst)
313
{
314
	const char *tgt_value;
315

316
	/* don't open twice */
317
	if (dst->initialized)
318
		return dst->fd;
319

320
	dst->initialized = 1;
321

322
	tgt_value = tr2_sysenv_get(dst->sysenv_var);
323

324
	if (!tgt_value || !strcmp(tgt_value, "") || !strcmp(tgt_value, "0") ||
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	    !strcasecmp(tgt_value, "false")) {
326
		dst->fd = 0;
327
		return dst->fd;
328
	}
329

330
	if (!strcmp(tgt_value, "1") || !strcasecmp(tgt_value, "true")) {
331
		dst->fd = STDERR_FILENO;
332
		return dst->fd;
333
	}
334

335
	if (strlen(tgt_value) == 1 && isdigit(*tgt_value)) {
336
		dst->fd = atoi(tgt_value);
337
		return dst->fd;
338
	}
339

340
	if (is_absolute_path(tgt_value)) {
341
		if (is_directory(tgt_value))
342
			return tr2_dst_try_auto_path(dst, tgt_value);
343
		else
344
			return tr2_dst_try_path(dst, tgt_value);
345
	}
346

347
#ifndef NO_UNIX_SOCKETS
348
	if (starts_with(tgt_value, PREFIX_AF_UNIX))
349
		return tr2_dst_try_unix_domain_socket(dst, tgt_value);
350
#endif
351

352
	/* Always warn about malformed values. */
353
	tr2_dst_malformed_warning(dst, tgt_value);
354
	tr2_dst_trace_disable(dst);
355
	return 0;
356
}
357

358
int tr2_dst_trace_want(struct tr2_dst *dst)
359
{
360
	return !!tr2_dst_get_trace_fd(dst);
361
}
362

363
void tr2_dst_write_line(struct tr2_dst *dst, struct strbuf *buf_line)
364
{
365
	int fd = tr2_dst_get_trace_fd(dst);
366
	ssize_t bytes;
367

368
	strbuf_complete_line(buf_line); /* ensure final NL on buffer */
369

370
	/*
371
	 * We do not use write_in_full() because we do not want
372
	 * a short-write to try again.  We are using O_APPEND mode
373
	 * files and the kernel handles the atomic seek+write. If
374
	 * another thread or git process is concurrently writing to
375
	 * this fd or file, our remainder-write may not be contiguous
376
	 * with our initial write of this message.  And that will
377
	 * confuse readers.  So just don't bother.
378
	 *
379
	 * It is assumed that TRACE2 messages are short enough that
380
	 * the system can write them in 1 attempt and we won't see
381
	 * a short-write.
382
	 *
383
	 * If we get an IO error, just close the trace dst.
384
	 */
385
	sigchain_push(SIGPIPE, SIG_IGN);
386
	bytes = write(fd, buf_line->buf, buf_line->len);
387
	sigchain_pop(SIGPIPE);
388
	if (bytes >= 0)
389
		return;
390

391
	tr2_dst_trace_disable(dst);
392
	if (tr2_dst_want_warning())
393
		warning("unable to write trace to '%s': %s",
394
			tr2_sysenv_display_name(dst->sysenv_var),
395
			strerror(errno));
396
}
397