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tag: v0.99.7c
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#include "cache.h"
#include "pkt-line.h"
#include <signal.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netdb.h>
#include <netinet/in.h>

static const char daemon_usage[] = "git-daemon [--inetd | --port=n]";

static int upload(char *dir, int dirlen)
{
if (chdir(dir) < 0)
return -1;
chdir(".git");

/*
* Security on the cheap.
*
* We want a readable HEAD, usable "objects" directory, and
* a "git-daemon-export-ok" flag that says that the other side
* is ok with us doing this.
*/
if (access("git-daemon-export-ok", F_OK) ||
access("objects/00", X_OK) ||
access("HEAD", R_OK))
return -1;

/*
* We'll ignore SIGTERM from now on, we have a
* good client.
*/
signal(SIGTERM, SIG_IGN);

/* git-upload-pack only ever reads stuff, so this is safe */
execlp("git-upload-pack", "git-upload-pack", ".", NULL);
return -1;
}

static int execute(void)
{
static char line[1000];
int len;

len = packet_read_line(0, line, sizeof(line));

if (len && line[len-1] == '\n')
line[--len] = 0;

if (!strncmp("git-upload-pack /", line, 17))
return upload(line + 16, len - 16);

fprintf(stderr, "got bad connection '%s'\n", line);
return -1;
}


/*
* 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 = 0;
static pid_t dead_child[MAX_CHILDREN];

/* These are updated by the main loop */
static unsigned int children_spawned = 0;
static unsigned int children_deleted = 0;

static struct child {
pid_t pid;
int addrlen;
struct sockaddr_storage address;
} live_child[MAX_CHILDREN];

static void add_child(int idx, 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);
}

/*
* Walk from "deleted" to "spawned", and remove child "pid".
*
* 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)
{
struct child n;

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;
}
}

/*
* 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.
*/
static void kill_some_children(int signo, unsigned start, unsigned stop)
{
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_max_connections(void)
{
for (;;) {
int active;
unsigned spawned, reaped, deleted;

spawned = children_spawned;
reaped = children_reaped;
deleted = children_deleted;

while (deleted < reaped) {
pid_t pid = dead_child[deleted % MAX_CHILDREN];
remove_child(pid, deleted, spawned);
deleted++;
}
children_deleted = 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;

/* If the SIGTERM thing isn't helping use SIGKILL */
kill_some_children(SIGKILL, deleted, spawned);
sleep(1);
}
}

static void handle(int incoming, struct sockaddr *addr, int addrlen)
{
pid_t pid = fork();

if (pid) {
unsigned idx;

close(incoming);
if (pid < 0)
return;

idx = children_spawned % MAX_CHILDREN;
children_spawned++;
add_child(idx, pid, addr, addrlen);

check_max_connections();
return;
}

dup2(incoming, 0);
dup2(incoming, 1);
close(incoming);
exit(execute());
}

static void child_handler(int signo)
{
for (;;) {
pid_t pid = waitpid(-1, NULL, WNOHANG);

if (pid > 0) {
unsigned reaped = children_reaped;
dead_child[reaped % MAX_CHILDREN] = pid;
children_reaped = reaped + 1;
continue;
}
break;
}
}

static int serve(int port)
{
struct addrinfo hints, *ai0, *ai;
int gai;
int socknum = 0, *socklist = NULL;
int maxfd = -1;
fd_set fds_init, fds;
char pbuf[NI_MAXSERV];

signal(SIGCHLD, child_handler);

sprintf(pbuf, "%d", port);
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;

gai = getaddrinfo(NULL, pbuf, &hints, &ai0);
if (gai)
die("getaddrinfo() failed: %s\n", gai_strerror(gai));

FD_ZERO(&fds_init);

for (ai = ai0; ai; ai = ai->ai_next) {
int sockfd;
int *newlist;

sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
if (sockfd < 0)
continue;
if (sockfd >= FD_SETSIZE) {
error("too large socket descriptor.");
close(sockfd);
continue;
}

#ifdef IPV6_V6ONLY
if (ai->ai_family == AF_INET6) {
int on = 1;
setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
&on, sizeof(on));
/* Note: error is not fatal */
}
#endif

if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
close(sockfd);
continue; /* not fatal */
}
if (listen(sockfd, 5) < 0) {
close(sockfd);
continue; /* not fatal */
}

newlist = realloc(socklist, sizeof(int) * (socknum + 1));
if (!newlist)
die("memory allocation failed: %s", strerror(errno));

socklist = newlist;
socklist[socknum++] = sockfd;

FD_SET(sockfd, &fds_init);
if (maxfd < sockfd)
maxfd = sockfd;
}

freeaddrinfo(ai0);

if (socknum == 0)
die("unable to allocate any listen sockets on port %u", port);

for (;;) {
int i;
fds = fds_init;

if (select(maxfd + 1, &fds, NULL, NULL, NULL) < 0) {
if (errno != EINTR) {
error("select failed, resuming: %s",
strerror(errno));
sleep(1);
}
continue;
}

for (i = 0; i < socknum; i++) {
int sockfd = socklist[i];

if (FD_ISSET(sockfd, &fds)) {
struct sockaddr_storage ss;
int sslen = sizeof(ss);
int incoming = accept(sockfd, (struct sockaddr *)&ss, &sslen);
if (incoming < 0) {
switch (errno) {
case EAGAIN:
case EINTR:
case ECONNABORTED:
continue;
default:
die("accept returned %s", strerror(errno));
}
}
handle(incoming, (struct sockaddr *)&ss, sslen);
}
}
}
}

int main(int argc, char **argv)
{
int port = DEFAULT_GIT_PORT;
int inetd_mode = 0;
int i;

for (i = 1; i < argc; i++) {
char *arg = argv[i];

if (!strncmp(arg, "--port=", 7)) {
char *end;
unsigned long n;
n = strtoul(arg+7, &end, 0);
if (arg[7] && !*end) {
port = n;
continue;
}
}

if (!strcmp(arg, "--inetd")) {
inetd_mode = 1;
continue;
}

usage(daemon_usage);
}

if (inetd_mode) {
fclose(stderr); //FIXME: workaround
return execute();
}

return serve(port);
}
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