[PATCH] Add documentation for git-rename-script
[git/git.git] / daemon.c
CommitLineData
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1#include "cache.h"
2#include "pkt-line.h"
eaa94919
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3#include <signal.h>
4#include <sys/wait.h>
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5#include <sys/socket.h>
6#include <netinet/in.h>
66e631de 7#include <arpa/inet.h>
a87e8be2 8
e64e1b79 9static const char daemon_usage[] = "git-daemon [--inetd | --port=n]";
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10
11static 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
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29 /*
30 * We'll ignore SIGTERM from now on, we have a
31 * good client.
32 */
33 signal(SIGTERM, SIG_IGN);
34
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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
7d80694a 40static int execute(void)
a87e8be2 41{
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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
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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
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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
70static int max_connections = 25;
71
72/* These are updated by the signal handler */
73static volatile unsigned int children_reaped = 0;
74pid_t dead_child[MAX_CHILDREN];
75
76/* These are updated by the main loop */
77static unsigned int children_spawned = 0;
78static unsigned int children_deleted = 0;
79
80struct child {
81 pid_t pid;
82 int addrlen;
83 struct sockaddr_in address;
84} live_child[MAX_CHILDREN];
85
86static 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 */
99static 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 */
02d57da4 137static void kill_some_children(int signo, unsigned start, unsigned stop)
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138{
139 start %= MAX_CHILDREN;
140 stop %= MAX_CHILDREN;
141 while (start != stop) {
142 if (!(start & 3))
02d57da4 143 kill(live_child[start].pid, signo);
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144 start = (start + 1) % MAX_CHILDREN;
145 }
146}
147
02d57da4 148static void check_max_connections(void)
a87e8be2 149{
02d57da4 150 for (;;) {
eaa94919 151 int active;
66e631de 152 unsigned spawned, reaped, deleted;
eaa94919 153
66e631de 154 spawned = children_spawned;
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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;
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166 if (active <= max_connections)
167 break;
66e631de 168
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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
180static 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);
66e631de 194
02d57da4 195 check_max_connections();
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196 return;
197 }
198
199 dup2(incoming, 0);
200 dup2(incoming, 1);
201 close(incoming);
7d80694a 202 exit(execute());
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203}
204
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205static void child_handler(int signo)
206{
207 for (;;) {
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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;
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214 continue;
215 }
216 break;
217 }
218}
219
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220static int serve(int port)
221{
222 int sockfd;
223 struct sockaddr_in addr;
224
eaa94919 225 signal(SIGCHLD, child_handler);
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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
256int main(int argc, char **argv)
257{
258 int port = DEFAULT_GIT_PORT;
e64e1b79 259 int inetd_mode = 0;
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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 }
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274
275 if (!strcmp(arg, "--inetd")) {
276 inetd_mode = 1;
277 continue;
278 }
279
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280 usage(daemon_usage);
281 }
282
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283 if (inetd_mode)
284 return execute();
285
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286 return serve(port);
287}