#include "cache.h"
#include "pkt-line.h"
#include "exec_cmd.h"
#include "interpolate.h"

#include <syslog.h>

#ifndef HOST_NAME_MAX
#define HOST_NAME_MAX 256
#endif

#ifndef NI_MAXSERV
#define NI_MAXSERV 32
#endif

static int log_syslog;
static int verbose;
static int reuseaddr;
static int child_handler_pipe[2];

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"
"           [--user-path | --user-path=path]\n"
"           [--interpolated-path=path]\n"
"           [--reuseaddr] [--detach] [--pid-file=file]\n"
"           [--[enable|disable|allow-override|forbid-override]=service]\n"
"           [--inetd | [--listen=host_or_ipaddr] [--port=n]\n"
"                      [--user=user [--group=group]]\n"
"           [directory...]";

/* List of acceptable pathname prefixes */
static char **ok_paths;
static int strict_paths;

/* If this is set, git-daemon-export-ok is not required */
static int export_all_trees;

/* Take all paths relative to this one if non-NULL */
static char *base_path;
static char *interpolated_path;
static int base_path_relaxed;

/* Flag indicating client sent extra args. */
static int saw_extended_args;

/* If defined, ~user notation is allowed and the string is inserted
 * after ~user/.  E.g. a request to git://host/~alice/frotz would
 * go to /home/alice/pub_git/frotz with --user-path=pub_git.
 */
static const char *user_path;

/* Timeout, and initial timeout */
static unsigned int timeout;
static unsigned int init_timeout;

/*
 * Static table for now.  Ugh.
 * Feel free to make dynamic as needed.
 */
#define INTERP_SLOT_HOST        (0)
#define INTERP_SLOT_CANON_HOST  (1)
#define INTERP_SLOT_IP          (2)
#define INTERP_SLOT_PORT        (3)
#define INTERP_SLOT_DIR         (4)
#define INTERP_SLOT_PERCENT     (5)

static struct interp interp_table[] = {
        { "%H", 0},
        { "%CH", 0},
        { "%IP", 0},
        { "%P", 0},
        { "%D", 0},
        { "%%", 0},
};


static void logreport(int priority, const char *err, va_list params)
{
        /* We should do a single write so that it is atomic and output
         * of several processes do not get intermingled. */
        char buf[1024];
        int buflen;
        int maxlen, msglen;

        /* sizeof(buf) should be big enough for "[pid] \n" */
        buflen = snprintf(buf, sizeof(buf), "[%ld] ", (long) getpid());

        maxlen = sizeof(buf) - buflen - 1; /* -1 for our own LF */
        msglen = vsnprintf(buf + buflen, maxlen, err, params);

        if (log_syslog) {
                syslog(priority, "%s", buf);
                return;
        }

        /* maxlen counted our own LF but also counts space given to
         * vsnprintf for the terminating NUL.  We want to make sure that
         * we have space for our own LF and NUL after the "meat" of the
         * message, so truncate it at maxlen - 1.
         */
        if (msglen > maxlen - 1)
                msglen = maxlen - 1;
        else if (msglen < 0)
                msglen = 0; /* Protect against weird return values. */
        buflen += msglen;

        buf[buflen++] = '\n';
        buf[buflen] = '\0';

        write_in_full(2, buf, buflen);
}

static void logerror(const char *err, ...)
{
        va_list params;
        va_start(params, err);
        logreport(LOG_ERR, err, params);
        va_end(params);
}

static void loginfo(const char *err, ...)
{
        va_list params;
        if (!verbose)
                return;
        va_start(params, err);
        logreport(LOG_INFO, err, params);
        va_end(params);
}

static void NORETURN daemon_die(const char *err, va_list params)
{
        logreport(LOG_ERR, err, params);
        exit(1);
}

static int avoid_alias(char *p)
{
        int sl, ndot;

        /*
         * This resurrects the belts and suspenders paranoia check by HPA
         * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
         * does not do getcwd() based path canonicalizations.
         *
         * sl becomes true immediately after seeing '/' and continues to
         * be true as long as dots continue after that without intervening
         * non-dot character.
         */
        if (!p || (*p != '/' && *p != '~'))
                return -1;
        sl = 1; ndot = 0;
        p++;

        while (1) {
                char ch = *p++;
                if (sl) {
                        if (ch == '.')
                                ndot++;
                        else if (ch == '/') {
                                if (ndot < 3)
                                        /* reject //, /./ and /../ */
                                        return -1;
                                ndot = 0;
                        }
                        else if (ch == 0) {
                                if (0 < ndot && ndot < 3)
                                        /* reject /.$ and /..$ */
                                        return -1;
                                return 0;
                        }
                        else
                                sl = ndot = 0;
                }
                else if (ch == 0)
                        return 0;
                else if (ch == '/') {
                        sl = 1;
                        ndot = 0;
                }
        }
}

static char *path_ok(struct interp *itable)
{
        static char rpath[PATH_MAX];
        static char interp_path[PATH_MAX];
        int retried_path = 0;
        char *path;
        char *dir;

        dir = itable[INTERP_SLOT_DIR].value;

        if (avoid_alias(dir)) {
                logerror("'%s': aliased", dir);
                return NULL;
        }

        if (*dir == '~') {
                if (!user_path) {
                        logerror("'%s': User-path not allowed", dir);
                        return NULL;
                }
                if (*user_path) {
                        /* Got either "~alice" or "~alice/foo";
                         * rewrite them to "~alice/%s" or
                         * "~alice/%s/foo".
                         */
                        int namlen, restlen = strlen(dir);
                        char *slash = strchr(dir, '/');
                        if (!slash)
                                slash = dir + restlen;
                        namlen = slash - dir;
                        restlen -= namlen;
                        loginfo("userpath <%s>, request <%s>, namlen %d, restlen %d, slash <%s>", user_path, dir, namlen, restlen, slash);
                        snprintf(rpath, PATH_MAX, "%.*s/%s%.*s",
                                 namlen, dir, user_path, restlen, slash);
                        dir = rpath;
                }
        }
        else if (interpolated_path && saw_extended_args) {
                if (*dir != '/') {
                        /* Allow only absolute */
                        logerror("'%s': Non-absolute path denied (interpolated-path active)", dir);
                        return NULL;
                }

                interpolate(interp_path, PATH_MAX, interpolated_path,
                            interp_table, ARRAY_SIZE(interp_table));
                loginfo("Interpolated dir '%s'", interp_path);

                dir = interp_path;
        }
        else if (base_path) {
                if (*dir != '/') {
                        /* Allow only absolute */
                        logerror("'%s': Non-absolute path denied (base-path active)", dir);
                        return NULL;
                }
                snprintf(rpath, PATH_MAX, "%s%s", base_path, dir);
                dir = rpath;
        }

        do {
                path = enter_repo(dir, strict_paths);
                if (path)
                        break;

                /*
                 * if we fail and base_path_relaxed is enabled, try without
                 * prefixing the base path
                 */
                if (base_path && base_path_relaxed && !retried_path) {
                        dir = itable[INTERP_SLOT_DIR].value;
                        retried_path = 1;
                        continue;
                }
                break;
        } while (1);

        if (!path) {
                logerror("'%s': unable to chdir or not a git archive", dir);
                return NULL;
        }

        if ( ok_paths && *ok_paths ) {
                char **pp;
                int pathlen = strlen(path);

                /* The validation is done on the paths after enter_repo
                 * appends optional {.git,.git/.git} and friends, but
                 * it does not use getcwd().  So if your /pub is
                 * a symlink to /mnt/pub, you can whitelist /pub and
                 * do not have to say /mnt/pub.
                 * Do not say /pub/.
                 */
                for ( pp = ok_paths ; *pp ; pp++ ) {
                        int len = strlen(*pp);
                        if (len <= pathlen &&
                            !memcmp(*pp, path, len) &&
                            (path[len] == '\0' ||
                             (!strict_paths && path[len] == '/')))
                                return path;
                }
        }
        else {
                /* be backwards compatible */
                if (!strict_paths)
                        return path;
        }

        logerror("'%s': not in whitelist", path);
        return NULL;            /* Fallthrough. Deny by default */
}

typedef int (*daemon_service_fn)(void);
struct daemon_service {
        const char *name;
        const char *config_name;
        daemon_service_fn fn;
        int enabled;
        int overridable;
};

static struct daemon_service *service_looking_at;
static int service_enabled;

static int git_daemon_config(const char *var, const char *value, void *cb)
{
        if (!prefixcmp(var, "daemon.") &&
            !strcmp(var + 7, service_looking_at->config_name)) {
                service_enabled = git_config_bool(var, value);
                return 0;
        }

        /* we are not interested in parsing any other configuration here */
        return 0;
}

static int run_service(struct interp *itable, struct daemon_service *service)
{
        const char *path;
        int enabled = service->enabled;

        loginfo("Request %s for '%s'",
                service->name,
                itable[INTERP_SLOT_DIR].value);

        if (!enabled && !service->overridable) {
                logerror("'%s': service not enabled.", service->name);
                errno = EACCES;
                return -1;
        }

        if (!(path = path_ok(itable)))
                return -1;

        /*
         * 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.
         *
         * path_ok() uses enter_repo() and does whitelist checking.
         * We only need to make sure the repository is exported.
         */

        if (!export_all_trees && access("git-daemon-export-ok", F_OK)) {
                logerror("'%s': repository not exported.", path);
                errno = EACCES;
                return -1;
        }

        if (service->overridable) {
                service_looking_at = service;
                service_enabled = -1;
                git_config(git_daemon_config, NULL);
                if (0 <= service_enabled)
                        enabled = service_enabled;
        }
        if (!enabled) {
                logerror("'%s': service not enabled for '%s'",
                         service->name, path);
                errno = EACCES;
                return -1;
        }

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

        return service->fn();
}

static int upload_pack(void)
{
        /* Timeout as string */
        char timeout_buf[64];

        snprintf(timeout_buf, sizeof timeout_buf, "--timeout=%u", timeout);

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

static int upload_archive(void)
{
        execl_git_cmd("upload-archive", ".", NULL);
        return -1;
}

static int receive_pack(void)
{
        execl_git_cmd("receive-pack", ".", NULL);
        return -1;
}

static struct daemon_service daemon_service[] = {
        { "upload-archive", "uploadarch", upload_archive, 0, 1 },
        { "upload-pack", "uploadpack", upload_pack, 1, 1 },
        { "receive-pack", "receivepack", receive_pack, 0, 1 },
};

static void enable_service(const char *name, int ena)
{
        int i;
        for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
                if (!strcmp(daemon_service[i].name, name)) {
                        daemon_service[i].enabled = ena;
                        return;
                }
        }
        die("No such service %s", name);
}

static void make_service_overridable(const char *name, int ena)
{
        int i;
        for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
                if (!strcmp(daemon_service[i].name, name)) {
                        daemon_service[i].overridable = ena;
                        return;
                }
        }
        die("No such service %s", name);
}

/*
 * Separate the "extra args" information as supplied by the client connection.
 * Any resulting data is squirreled away in the given interpolation table.
 */
static void parse_extra_args(struct interp *table, char *extra_args, int buflen)
{
        char *val;
        int vallen;
        char *end = extra_args + buflen;

        while (extra_args < end && *extra_args) {
                saw_extended_args = 1;
                if (strncasecmp("host=", extra_args, 5) == 0) {
                        val = extra_args + 5;
                        vallen = strlen(val) + 1;
                        if (*val) {
                                /* Split <host>:<port> at colon. */
                                char *host = val;
                                char *port = strrchr(host, ':');
                                if (port) {
                                        *port = 0;
                                        port++;
                                        interp_set_entry(table, INTERP_SLOT_PORT, port);
                                }
                                interp_set_entry(table, INTERP_SLOT_HOST, host);
                        }

                        /* On to the next one */
                        extra_args = val + vallen;
                }
        }
}

static void fill_in_extra_table_entries(struct interp *itable)
{
        char *hp;

        /*
         * Replace literal host with lowercase-ized hostname.
         */
        hp = interp_table[INTERP_SLOT_HOST].value;
        if (!hp)
                return;
        for ( ; *hp; hp++)
                *hp = tolower(*hp);

        /*
         * Locate canonical hostname and its IP address.
         */
#ifndef NO_IPV6
        {
                struct addrinfo hints;
                struct addrinfo *ai, *ai0;
                int gai;
                static char addrbuf[HOST_NAME_MAX + 1];

                memset(&hints, 0, sizeof(hints));
                hints.ai_flags = AI_CANONNAME;

                gai = getaddrinfo(interp_table[INTERP_SLOT_HOST].value, 0, &hints, &ai0);
                if (!gai) {
                        for (ai = ai0; ai; ai = ai->ai_next) {
                                struct sockaddr_in *sin_addr = (void *)ai->ai_addr;

                                inet_ntop(AF_INET, &sin_addr->sin_addr,
                                          addrbuf, sizeof(addrbuf));
                                interp_set_entry(interp_table,
                                                 INTERP_SLOT_CANON_HOST, ai->ai_canonname);
                                interp_set_entry(interp_table,
                                                 INTERP_SLOT_IP, addrbuf);
                                break;
                        }
                        freeaddrinfo(ai0);
                }
        }
#else
        {
                struct hostent *hent;
                struct sockaddr_in sa;
                char **ap;
                static char addrbuf[HOST_NAME_MAX + 1];

                hent = gethostbyname(interp_table[INTERP_SLOT_HOST].value);

                ap = hent->h_addr_list;
                memset(&sa, 0, sizeof sa);
                sa.sin_family = hent->h_addrtype;
                sa.sin_port = htons(0);
                memcpy(&sa.sin_addr, *ap, hent->h_length);

                inet_ntop(hent->h_addrtype, &sa.sin_addr,
                          addrbuf, sizeof(addrbuf));

                interp_set_entry(interp_table, INTERP_SLOT_CANON_HOST, hent->h_name);
                interp_set_entry(interp_table, INTERP_SLOT_IP, addrbuf);
        }
#endif
}


static int execute(struct sockaddr *addr)
{
        static char line[1000];
        int pktlen, len, i;

        if (addr) {
                char addrbuf[256] = "";
                int port = -1;

                if (addr->sa_family == AF_INET) {
                        struct sockaddr_in *sin_addr = (void *) addr;
                        inet_ntop(addr->sa_family, &sin_addr->sin_addr, addrbuf, sizeof(addrbuf));
                        port = ntohs(sin_addr->sin_port);
#ifndef NO_IPV6
                } else if (addr && addr->sa_family == AF_INET6) {
                        struct sockaddr_in6 *sin6_addr = (void *) addr;

                        char *buf = addrbuf;
                        *buf++ = '['; *buf = '\0'; /* stpcpy() is cool */
                        inet_ntop(AF_INET6, &sin6_addr->sin6_addr, buf, sizeof(addrbuf) - 1);
                        strcat(buf, "]");

                        port = ntohs(sin6_addr->sin6_port);
#endif
                }
                loginfo("Connection from %s:%d", addrbuf, port);
        }

        alarm(init_timeout ? init_timeout : timeout);
        pktlen = packet_read_line(0, line, sizeof(line));
        alarm(0);

        len = strlen(line);
        if (pktlen != len)
                loginfo("Extended attributes (%d bytes) exist <%.*s>",
                        (int) pktlen - len,
                        (int) pktlen - len, line + len + 1);
        if (len && line[len-1] == '\n') {
                line[--len] = 0;
                pktlen--;
        }

        /*
         * Initialize the path interpolation table for this connection.
         */
        interp_clear_table(interp_table, ARRAY_SIZE(interp_table));
        interp_set_entry(interp_table, INTERP_SLOT_PERCENT, "%");

        if (len != pktlen) {
            parse_extra_args(interp_table, line + len + 1, pktlen - len - 1);
            fill_in_extra_table_entries(interp_table);
        }

        for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
                struct daemon_service *s = &(daemon_service[i]);
                int namelen = strlen(s->name);
                if (!prefixcmp(line, "git-") &&
                    !strncmp(s->name, line + 4, namelen) &&
                    line[namelen + 4] == ' ') {
                        /*
                         * Note: The directory here is probably context sensitive,
                         * and might depend on the actual service being performed.
                         */
                        interp_set_entry(interp_table,
                                         INTERP_SLOT_DIR, line + namelen + 5);
                        return run_service(interp_table, s);
                }
        }

        logerror("Protocol error: '%s'", 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;
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 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_dead_children(void)
{
        unsigned spawned, reaped, deleted;

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

        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++;
        }
        children_deleted = deleted;
}

static void check_max_connections(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;

                /* 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(addr));
}

static void child_handler(int signo)
{
        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;
                        write(child_handler_pipe[1], &status, 1);
                        continue;
                }
                break;
        }
        signal(SIGCHLD, child_handler);
}

static int set_reuse_addr(int sockfd)
{
        int on = 1;

        if (!reuseaddr)
                return 0;
        return setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,
                          &on, sizeof(on));
}

#ifndef NO_IPV6

static int socksetup(char *listen_addr, int listen_port, int **socklist_p)
{
        int socknum = 0, *socklist = NULL;
        int maxfd = -1;
        char pbuf[NI_MAXSERV];
        struct addrinfo hints, *ai0, *ai;
        int gai;
        long flags;

        sprintf(pbuf, "%d", listen_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(listen_addr, pbuf, &hints, &ai0);
        if (gai)
                die("getaddrinfo() failed: %s\n", gai_strerror(gai));

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

                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 (set_reuse_addr(sockfd)) {
                        close(sockfd);
                        continue;
                }

                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 */
                }

                flags = fcntl(sockfd, F_GETFD, 0);
                if (flags >= 0)
                        fcntl(sockfd, F_SETFD, flags | FD_CLOEXEC);

                socklist = xrealloc(socklist, sizeof(int) * (socknum + 1));
                socklist[socknum++] = sockfd;

                if (maxfd < sockfd)
                        maxfd = sockfd;
        }

        freeaddrinfo(ai0);

        *socklist_p = socklist;
        return socknum;
}

#else /* NO_IPV6 */

static int socksetup(char *listen_addr, int listen_port, int **socklist_p)
{
        struct sockaddr_in sin;
        int sockfd;
        long flags;

        memset(&sin, 0, sizeof sin);
        sin.sin_family = AF_INET;
        sin.sin_port = htons(listen_port);

        if (listen_addr) {
                /* Well, host better be an IP address here. */
                if (inet_pton(AF_INET, listen_addr, &sin.sin_addr.s_addr) <= 0)
                        return 0;
        } else {
                sin.sin_addr.s_addr = htonl(INADDR_ANY);
        }

        sockfd = socket(AF_INET, SOCK_STREAM, 0);
        if (sockfd < 0)
                return 0;

        if (set_reuse_addr(sockfd)) {
                close(sockfd);
                return 0;
        }

        if ( bind(sockfd, (struct sockaddr *)&sin, sizeof sin) < 0 ) {
                close(sockfd);
                return 0;
        }

        if (listen(sockfd, 5) < 0) {
                close(sockfd);
                return 0;
        }

        flags = fcntl(sockfd, F_GETFD, 0);
        if (flags >= 0)
                fcntl(sockfd, F_SETFD, flags | FD_CLOEXEC);

        *socklist_p = xmalloc(sizeof(int));
        **socklist_p = sockfd;
        return 1;
}

#endif

static int service_loop(int socknum, int *socklist)
{
        struct pollfd *pfd;
        int i;

        if (pipe(child_handler_pipe) < 0)
                die ("Could not set up pipe for child handler");

        pfd = xcalloc(socknum + 1, sizeof(struct pollfd));

        for (i = 0; i < socknum; i++) {
                pfd[i].fd = socklist[i];
                pfd[i].events = POLLIN;
        }
        pfd[socknum].fd = child_handler_pipe[0];
        pfd[socknum].events = POLLIN;

        signal(SIGCHLD, child_handler);

        for (;;) {
                int i;

                if (poll(pfd, socknum + 1, -1) < 0) {
                        if (errno != EINTR) {
                                error("poll failed, resuming: %s",
                                      strerror(errno));
                                sleep(1);
                        }
                        continue;
                }
                if (pfd[socknum].revents & POLLIN) {
                        read(child_handler_pipe[0], &i, 1);
                        check_dead_children();
                }

                for (i = 0; i < socknum; i++) {
                        if (pfd[i].revents & POLLIN) {
                                struct sockaddr_storage ss;
                                unsigned int sslen = sizeof(ss);
                                int incoming = accept(pfd[i].fd, (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);
                        }
                }
        }
}

/* if any standard file descriptor is missing open it to /dev/null */
static void sanitize_stdfds(void)
{
        int fd = open("/dev/null", O_RDWR, 0);
        while (fd != -1 && fd < 2)
                fd = dup(fd);
        if (fd == -1)
                die("open /dev/null or dup failed: %s", strerror(errno));
        if (fd > 2)
                close(fd);
}

static void daemonize(void)
{
        switch (fork()) {
                case 0:
                        break;
                case -1:
                        die("fork failed: %s", strerror(errno));
                default:
                        exit(0);
        }
        if (setsid() == -1)
                die("setsid failed: %s", strerror(errno));
        close(0);
        close(1);
        close(2);
        sanitize_stdfds();
}

static void store_pid(const char *path)
{
        FILE *f = fopen(path, "w");
        if (!f)
                die("cannot open pid file %s: %s", path, strerror(errno));
        if (fprintf(f, "%d\n", getpid()) < 0 || fclose(f) != 0)
                die("failed to write pid file %s: %s", path, strerror(errno));
}

static int serve(char *listen_addr, int listen_port, struct passwd *pass, gid_t gid)
{
        int socknum, *socklist;

        socknum = socksetup(listen_addr, listen_port, &socklist);
        if (socknum == 0)
                die("unable to allocate any listen sockets on host %s port %u",
                    listen_addr, listen_port);

        if (pass && gid &&
            (initgroups(pass->pw_name, gid) || setgid (gid) ||
             setuid(pass->pw_uid)))
                die("cannot drop privileges");

        return service_loop(socknum, socklist);
}

int main(int argc, char **argv)
{
        int listen_port = 0;
        char *listen_addr = NULL;
        int inetd_mode = 0;
        const char *pid_file = NULL, *user_name = NULL, *group_name = NULL;
        int detach = 0;
        struct passwd *pass = NULL;
        struct group *group;
        gid_t gid = 0;
        int i;

        /* Without this we cannot rely on waitpid() to tell
         * what happened to our children.
         */
        signal(SIGCHLD, SIG_DFL);

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

                if (!prefixcmp(arg, "--listen=")) {
                    char *p = arg + 9;
                    char *ph = listen_addr = xmalloc(strlen(arg + 9) + 1);
                    while (*p)
                        *ph++ = tolower(*p++);
                    *ph = 0;
                    continue;
                }
                if (!prefixcmp(arg, "--port=")) {
                        char *end;
                        unsigned long n;
                        n = strtoul(arg+7, &end, 0);
                        if (arg[7] && !*end) {
                                listen_port = n;
                                continue;
                        }
                }
                if (!strcmp(arg, "--inetd")) {
                        inetd_mode = 1;
                        log_syslog = 1;
                        continue;
                }
                if (!strcmp(arg, "--verbose")) {
                        verbose = 1;
                        continue;
                }
                if (!strcmp(arg, "--syslog")) {
                        log_syslog = 1;
                        continue;
                }
                if (!strcmp(arg, "--export-all")) {
                        export_all_trees = 1;
                        continue;
                }
                if (!prefixcmp(arg, "--timeout=")) {
                        timeout = atoi(arg+10);
                        continue;
                }
                if (!prefixcmp(arg, "--init-timeout=")) {
                        init_timeout = atoi(arg+15);
                        continue;
                }
                if (!strcmp(arg, "--strict-paths")) {
                        strict_paths = 1;
                        continue;
                }
                if (!prefixcmp(arg, "--base-path=")) {
                        base_path = arg+12;
                        continue;
                }
                if (!strcmp(arg, "--base-path-relaxed")) {
                        base_path_relaxed = 1;
                        continue;
                }
                if (!prefixcmp(arg, "--interpolated-path=")) {
                        interpolated_path = arg+20;
                        continue;
                }
                if (!strcmp(arg, "--reuseaddr")) {
                        reuseaddr = 1;
                        continue;
                }
                if (!strcmp(arg, "--user-path")) {
                        user_path = "";
                        continue;
                }
                if (!prefixcmp(arg, "--user-path=")) {
                        user_path = arg + 12;
                        continue;
                }
                if (!prefixcmp(arg, "--pid-file=")) {
                        pid_file = arg + 11;
                        continue;
                }
                if (!strcmp(arg, "--detach")) {
                        detach = 1;
                        log_syslog = 1;
                        continue;
                }
                if (!prefixcmp(arg, "--user=")) {
                        user_name = arg + 7;
                        continue;
                }
                if (!prefixcmp(arg, "--group=")) {
                        group_name = arg + 8;
                        continue;
                }
                if (!prefixcmp(arg, "--enable=")) {
                        enable_service(arg + 9, 1);
                        continue;
                }
                if (!prefixcmp(arg, "--disable=")) {
                        enable_service(arg + 10, 0);
                        continue;
                }
                if (!prefixcmp(arg, "--allow-override=")) {
                        make_service_overridable(arg + 17, 1);
                        continue;
                }
                if (!prefixcmp(arg, "--forbid-override=")) {
                        make_service_overridable(arg + 18, 0);
                        continue;
                }
                if (!strcmp(arg, "--")) {
                        ok_paths = &argv[i+1];
                        break;
                } else if (arg[0] != '-') {
                        ok_paths = &argv[i];
                        break;
                }

                usage(daemon_usage);
        }

        if (log_syslog) {
                openlog("git-daemon", 0, LOG_DAEMON);
                set_die_routine(daemon_die);
        }

        if (inetd_mode && (group_name || user_name))
                die("--user and --group are incompatible with --inetd");

        if (inetd_mode && (listen_port || listen_addr))
                die("--listen= and --port= are incompatible with --inetd");
        else if (listen_port == 0)
                listen_port = DEFAULT_GIT_PORT;

        if (group_name && !user_name)
                die("--group supplied without --user");

        if (user_name) {
                pass = getpwnam(user_name);
                if (!pass)
                        die("user not found - %s", user_name);

                if (!group_name)
                        gid = pass->pw_gid;
                else {
                        group = getgrnam(group_name);
                        if (!group)
                                die("group not found - %s", group_name);

                        gid = group->gr_gid;
                }
        }

        if (strict_paths && (!ok_paths || !*ok_paths))
                die("option --strict-paths requires a whitelist");

        if (base_path) {
                struct stat st;

                if (stat(base_path, &st) || !S_ISDIR(st.st_mode))
                        die("base-path '%s' does not exist or "
                            "is not a directory", base_path);
        }

        if (inetd_mode) {
                struct sockaddr_storage ss;
                struct sockaddr *peer = (struct sockaddr *)&ss;
                socklen_t slen = sizeof(ss);

                freopen("/dev/null", "w", stderr);

                if (getpeername(0, peer, &slen))
                        peer = NULL;

                return execute(peer);
        }

        if (detach)
                daemonize();
        else
                sanitize_stdfds();

        if (pid_file)
                store_pid(pid_file);

        return serve(listen_addr, listen_port, pass, gid);
}