0ae9af0ad4d6c58d8c7cc0b615d8f9a7bc75572c
[git/git.git] / daemon.c
1 #include "cache.h"
2 #include "pkt-line.h"
3 #include <signal.h>
4 #include <sys/wait.h>
5 #include <sys/socket.h>
6 #include <netinet/in.h>
7 #include <arpa/inet.h>
8
9 static const char daemon_usage[] = "git-daemon [--inetd | --port=n]";
10
11 static int upload(char *dir, int dirlen)
12 {
13 if (chdir(dir) < 0)
14 return -1;
15 chdir(".git");
16
17 /*
18 * Security on the cheap.
19 *
20 * We want a readable HEAD, usable "objects" directory, and
21 * a "git-daemon-export-ok" flag that says that the other side
22 * is ok with us doing this.
23 */
24 if (access("git-daemon-export-ok", F_OK) ||
25 access("objects/00", X_OK) ||
26 access("HEAD", R_OK))
27 return -1;
28
29 /*
30 * We'll ignore SIGTERM from now on, we have a
31 * good client.
32 */
33 signal(SIGTERM, SIG_IGN);
34
35 /* git-upload-pack only ever reads stuff, so this is safe */
36 execlp("git-upload-pack", "git-upload-pack", ".", NULL);
37 return -1;
38 }
39
40 static int execute(void)
41 {
42 static char line[1000];
43 int len;
44
45 len = packet_read_line(0, line, sizeof(line));
46
47 if (len && line[len-1] == '\n')
48 line[--len] = 0;
49
50 if (!strncmp("git-upload-pack /", line, 17))
51 return upload(line + 16, len - 16);
52
53 fprintf(stderr, "got bad connection '%s'\n", line);
54 return -1;
55 }
56
57
58 /*
59 * We count spawned/reaped separately, just to avoid any
60 * races when updating them from signals. The SIGCHLD handler
61 * will only update children_reaped, and the fork logic will
62 * only update children_spawned.
63 *
64 * MAX_CHILDREN should be a power-of-two to make the modulus
65 * operation cheap. It should also be at least twice
66 * the maximum number of connections we will ever allow.
67 */
68 #define MAX_CHILDREN 128
69
70 static int max_connections = 25;
71
72 /* These are updated by the signal handler */
73 static volatile unsigned int children_reaped = 0;
74 pid_t dead_child[MAX_CHILDREN];
75
76 /* These are updated by the main loop */
77 static unsigned int children_spawned = 0;
78 static unsigned int children_deleted = 0;
79
80 struct child {
81 pid_t pid;
82 int addrlen;
83 struct sockaddr_in address;
84 } live_child[MAX_CHILDREN];
85
86 static void add_child(int idx, pid_t pid, struct sockaddr_in *addr, int addrlen)
87 {
88 live_child[idx].pid = pid;
89 live_child[idx].addrlen = addrlen;
90 live_child[idx].address = *addr;
91 }
92
93 /*
94 * Walk from "deleted" to "spawned", and remove child "pid".
95 *
96 * We move everything up by one, since the new "deleted" will
97 * be one higher.
98 */
99 static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
100 {
101 struct child n;
102
103 deleted %= MAX_CHILDREN;
104 spawned %= MAX_CHILDREN;
105 if (live_child[deleted].pid == pid) {
106 live_child[deleted].pid = -1;
107 return;
108 }
109 n = live_child[deleted];
110 for (;;) {
111 struct child m;
112 deleted = (deleted + 1) % MAX_CHILDREN;
113 if (deleted == spawned)
114 die("could not find dead child %d\n", pid);
115 m = live_child[deleted];
116 live_child[deleted] = n;
117 if (m.pid == pid)
118 return;
119 n = m;
120 }
121 }
122
123 /*
124 * This gets called if the number of connections grows
125 * past "max_connections".
126 *
127 * We _should_ start off by searching for connections
128 * from the same IP, and if there is some address wth
129 * multiple connections, we should kill that first.
130 *
131 * As it is, we just "randomly" kill 25% of the connections,
132 * and our pseudo-random generator sucks too. I have no
133 * shame.
134 *
135 * Really, this is just a place-holder for a _real_ algorithm.
136 */
137 static void kill_some_children(int signo, unsigned start, unsigned stop)
138 {
139 start %= MAX_CHILDREN;
140 stop %= MAX_CHILDREN;
141 while (start != stop) {
142 if (!(start & 3))
143 kill(live_child[start].pid, signo);
144 start = (start + 1) % MAX_CHILDREN;
145 }
146 }
147
148 static void check_max_connections(void)
149 {
150 for (;;) {
151 int active;
152 unsigned spawned, reaped, deleted;
153
154 spawned = children_spawned;
155 reaped = children_reaped;
156 deleted = children_deleted;
157
158 while (deleted < reaped) {
159 pid_t pid = dead_child[deleted % MAX_CHILDREN];
160 remove_child(pid, deleted, spawned);
161 deleted++;
162 }
163 children_deleted = deleted;
164
165 active = spawned - deleted;
166 if (active <= max_connections)
167 break;
168
169 /* Kill some unstarted connections with SIGTERM */
170 kill_some_children(SIGTERM, deleted, spawned);
171 if (active <= max_connections << 1)
172 break;
173
174 /* If the SIGTERM thing isn't helping use SIGKILL */
175 kill_some_children(SIGKILL, deleted, spawned);
176 sleep(1);
177 }
178 }
179
180 static void handle(int incoming, struct sockaddr_in *addr, int addrlen)
181 {
182 pid_t pid = fork();
183
184 if (pid) {
185 unsigned idx;
186
187 close(incoming);
188 if (pid < 0)
189 return;
190
191 idx = children_spawned % MAX_CHILDREN;
192 children_spawned++;
193 add_child(idx, pid, addr, addrlen);
194
195 check_max_connections();
196 return;
197 }
198
199 dup2(incoming, 0);
200 dup2(incoming, 1);
201 close(incoming);
202 exit(execute());
203 }
204
205 static void child_handler(int signo)
206 {
207 for (;;) {
208 pid_t pid = waitpid(-1, NULL, WNOHANG);
209
210 if (pid > 0) {
211 unsigned reaped = children_reaped;
212 dead_child[reaped % MAX_CHILDREN] = pid;
213 children_reaped = reaped + 1;
214 continue;
215 }
216 break;
217 }
218 }
219
220 static int serve(int port)
221 {
222 int sockfd;
223 struct sockaddr_in addr;
224
225 signal(SIGCHLD, child_handler);
226 sockfd = socket(PF_INET, SOCK_STREAM, IPPROTO_IP);
227 if (sockfd < 0)
228 die("unable to open socket (%s)", strerror(errno));
229 memset(&addr, 0, sizeof(addr));
230 addr.sin_port = htons(port);
231 addr.sin_family = AF_INET;
232 if (bind(sockfd, (void *)&addr, sizeof(addr)) < 0)
233 die("unable to bind to port %d (%s)", port, strerror(errno));
234 if (listen(sockfd, 5) < 0)
235 die("unable to listen to port %d (%s)", port, strerror(errno));
236
237 for (;;) {
238 struct sockaddr_in in;
239 socklen_t addrlen = sizeof(in);
240 int incoming = accept(sockfd, (void *)&in, &addrlen);
241
242 if (incoming < 0) {
243 switch (errno) {
244 case EAGAIN:
245 case EINTR:
246 case ECONNABORTED:
247 continue;
248 default:
249 die("accept returned %s", strerror(errno));
250 }
251 }
252 handle(incoming, &in, addrlen);
253 }
254 }
255
256 int main(int argc, char **argv)
257 {
258 int port = DEFAULT_GIT_PORT;
259 int inetd_mode = 0;
260 int i;
261
262 for (i = 1; i < argc; i++) {
263 char *arg = argv[i];
264
265 if (!strncmp(arg, "--port=", 7)) {
266 char *end;
267 unsigned long n;
268 n = strtoul(arg+7, &end, 0);
269 if (arg[7] && !*end) {
270 port = n;
271 continue;
272 }
273 }
274
275 if (!strcmp(arg, "--inetd")) {
276 inetd_mode = 1;
277 continue;
278 }
279
280 usage(daemon_usage);
281 }
282
283 if (inetd_mode)
284 return execute();
285
286 return serve(port);
287 }