Get rid of the fixed array of children and make max-connections
dynamic and configurable.
Fix the killing code to actually kill the newest connections from
duplicate IP-addresses.
Avoid forking if too busy already.
Signed-off-by: Stephen R. van den Berg <srb@xxxxxxx>
---
Documentation/git-daemon.txt | 9 +-
daemon.c | 213 +++++++++++++++---------------------------
2 files changed, 82 insertions(+), 140 deletions(-)
diff --git a/Documentation/git-daemon.txt b/Documentation/git-daemon.txt
index 4ba4b75..b08a08c 100644
--- a/Documentation/git-daemon.txt
+++ b/Documentation/git-daemon.txt
@@ -9,8 +9,9 @@ SYNOPSIS
--------
[verse]
'git daemon' [--verbose] [--syslog] [--export-all]
- [--timeout=n] [--init-timeout=n] [--strict-paths]
- [--base-path=path] [--user-path | --user-path=path]
+ [--timeout=n] [--init-timeout=n] [--max-connections=n]
+ [--strict-paths] [--base-path=path] [--base-path-relaxed]
+ [--user-path | --user-path=path]
[--interpolated-path=pathtemplate]
[--reuseaddr] [--detach] [--pid-file=file]
[--enable=service] [--disable=service]
@@ -99,6 +100,10 @@ OPTIONS
it takes for the server to process the sub-request and time spent
waiting for next client's request.
+--max-connections::
+ Maximum number of concurrent clients, defaults to 32. Set it to
+ zero for no limit.
+
--syslog::
Log to syslog instead of stderr. Note that this option does not imply
--verbose, thus by default only error conditions will be logged.
diff --git a/daemon.c b/daemon.c
index 77bd8e1..61a3920 100644
--- a/daemon.c
+++ b/daemon.c
@@ -19,8 +19,8 @@ static int reuseaddr;
static const char daemon_usage[] =
"git daemon [--verbose] [--syslog] [--export-all]\n"
-" [--timeout=n] [--init-timeout=n] [--strict-paths]\n"
-" [--base-path=path] [--base-path-relaxed]\n"
+" [--timeout=n] [--init-timeout=n] [--max-connections=n]\n"
+" [--strict-paths] [--base-path=path] [--base-path-relaxed]\n"
" [--user-path | --user-path=path]\n"
" [--interpolated-path=path]\n"
" [--reuseaddr] [--detach] [--pid-file=file]\n"
@@ -584,40 +584,35 @@ static int execute(struct sockaddr *addr)
return -1;
}
+static int max_connections = 32;
-/*
- * We count spawned/reaped separately, just to avoid any
- * races when updating them from signals. The SIGCHLD handler
- * will only update children_reaped, and the fork logic will
- * only update children_spawned.
- *
- * MAX_CHILDREN should be a power-of-two to make the modulus
- * operation cheap. It should also be at least twice
- * the maximum number of connections we will ever allow.
- */
-#define MAX_CHILDREN 128
-
-static int max_connections = 25;
-
-/* These are updated by the signal handler */
-static volatile unsigned int children_reaped;
-static pid_t dead_child[MAX_CHILDREN];
-
-/* These are updated by the main loop */
-static unsigned int children_spawned;
-static unsigned int children_deleted;
+static unsigned int live_children;
static struct child {
+ struct child *next;
pid_t pid;
- int addrlen;
struct sockaddr_storage address;
-} live_child[MAX_CHILDREN];
+} *firstborn;
-static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
+static void add_child(pid_t pid, struct sockaddr *addr, int addrlen)
{
- live_child[idx].pid = pid;
- live_child[idx].addrlen = addrlen;
- memcpy(&live_child[idx].address, addr, addrlen);
+ struct child *newborn;
+ newborn = xcalloc(1, sizeof *newborn);
+ if (newborn) {
+ struct child **cradle;
+
+ live_children++;
+ newborn->pid = pid;
+ memcpy(&newborn->address, addr, addrlen);
+ for (cradle = &firstborn; *cradle; cradle = &(*cradle)->next)
+ if (!memcmp(&(*cradle)->address, &newborn->address,
+ sizeof newborn->address))
+ break;
+ newborn->next = *cradle;
+ *cradle = newborn;
+ }
+ else
+ logerror("Out of memory spawning new child");
}
/*
@@ -626,142 +621,78 @@ static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
* We move everything up by one, since the new "deleted" will
* be one higher.
*/
-static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
+static void remove_child(pid_t pid)
{
- struct child n;
+ struct child **cradle, *blanket;
- deleted %= MAX_CHILDREN;
- spawned %= MAX_CHILDREN;
- if (live_child[deleted].pid == pid) {
- live_child[deleted].pid = -1;
- return;
- }
- n = live_child[deleted];
- for (;;) {
- struct child m;
- deleted = (deleted + 1) % MAX_CHILDREN;
- if (deleted == spawned)
- die("could not find dead child %d\n", pid);
- m = live_child[deleted];
- live_child[deleted] = n;
- if (m.pid == pid)
- return;
- n = m;
- }
+ for (cradle = &firstborn; (blanket = *cradle); cradle = &blanket->next)
+ if (blanket->pid == pid) {
+ *cradle = blanket->next;
+ live_children--;
+ free(blanket);
+ break;
+ }
}
/*
* This gets called if the number of connections grows
* past "max_connections".
*
- * We _should_ start off by searching for connections
- * from the same IP, and if there is some address wth
- * multiple connections, we should kill that first.
- *
- * As it is, we just "randomly" kill 25% of the connections,
- * and our pseudo-random generator sucks too. I have no
- * shame.
- *
- * Really, this is just a place-holder for a _real_ algorithm.
+ * We kill the newest connection from a duplicate IP.
*/
-static void kill_some_children(int signo, unsigned start, unsigned stop)
+static void kill_some_child()
{
- start %= MAX_CHILDREN;
- stop %= MAX_CHILDREN;
- while (start != stop) {
- if (!(start & 3))
- kill(live_child[start].pid, signo);
- start = (start + 1) % MAX_CHILDREN;
- }
-}
-
-static void check_dead_children(void)
-{
- unsigned spawned, reaped, deleted;
-
- for (;;) {
- int status;
- pid_t pid = waitpid(-1, &status, WNOHANG);
-
- if (pid > 0) {
- unsigned reaped = children_reaped;
- if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
- pid = -pid;
- dead_child[reaped % MAX_CHILDREN] = pid;
- children_reaped = reaped + 1;
- continue;
- }
- break;
- }
+ const struct child *blanket;
- spawned = children_spawned;
- reaped = children_reaped;
- deleted = children_deleted;
+ if ((blanket = firstborn)) {
+ const struct child *next;
- while (deleted < reaped) {
- pid_t pid = dead_child[deleted % MAX_CHILDREN];
- const char *dead = pid < 0 ? " (with error)" : "";
-
- if (pid < 0)
- pid = -pid;
-
- /* XXX: Custom logging, since we don't wanna getpid() */
- if (verbose) {
- if (log_syslog)
- syslog(LOG_INFO, "[%d] Disconnected%s",
- pid, dead);
- else
- fprintf(stderr, "[%d] Disconnected%s\n",
- pid, dead);
- }
- remove_child(pid, deleted, spawned);
- deleted++;
+ for (; (next = blanket->next); blanket = next)
+ if (!memcmp(&blanket->address, &next->address,
+ sizeof next->address)) {
+ kill(blanket->pid, SIGTERM);
+ break;
+ }
}
- children_deleted = deleted;
}
-static void check_max_connections(void)
+static void check_dead_children(void)
{
- for (;;) {
- int active;
- unsigned spawned, deleted;
-
- check_dead_children();
-
- spawned = children_spawned;
- deleted = children_deleted;
-
- active = spawned - deleted;
- if (active <= max_connections)
- break;
-
- /* Kill some unstarted connections with SIGTERM */
- kill_some_children(SIGTERM, deleted, spawned);
- if (active <= max_connections << 1)
- break;
+ int status;
+ pid_t pid;
- /* If the SIGTERM thing isn't helping use SIGKILL */
- kill_some_children(SIGKILL, deleted, spawned);
- sleep(1);
+ while ((pid = waitpid(-1, &status, WNOHANG))>0) {
+ const char *dead = "";
+ remove_child(pid);
+ if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
+ dead = " (with error)";
+ loginfo("[%d] Disconnected%s", (int)pid, dead);
}
}
static void handle(int incoming, struct sockaddr *addr, int addrlen)
{
- pid_t pid = fork();
+ pid_t pid;
- if (pid) {
- unsigned idx;
+ if (max_connections && live_children >= max_connections) {
+ kill_some_child();
+ sleep(1); /* give it some time to die */
+ check_dead_children();
+ if (live_children >= max_connections) {
+ close(incoming);
+ logerror("Too many children, dropping connection");
+ return;
+ }
+ }
+ if ((pid = fork())) {
close(incoming);
- if (pid < 0)
+ if (pid < 0) {
+ logerror("Couldn't fork %s", strerror(errno));
return;
+ }
- idx = children_spawned % MAX_CHILDREN;
- children_spawned++;
- add_child(idx, pid, addr, addrlen);
-
- check_max_connections();
+ add_child(pid, addr, addrlen);
return;
}
@@ -1077,6 +1008,12 @@ int main(int argc, char **argv)
init_timeout = atoi(arg+15);
continue;
}
+ if (!prefixcmp(arg, "--max-connections=")) {
+ max_connections = atoi(arg+18);
+ if (max_connections < 0)
+ max_connections = 0; /* unlimited */
+ continue;
+ }
if (!strcmp(arg, "--strict-paths")) {
strict_paths = 1;
continue;
--
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