sub-process.c

   1 /*
   2  * Generic implementation of background process infrastructure.
   3  */
   4 #include "sub-process.h"
   5 #include "sigchain.h"
   6 #include "pkt-line.h"
   7
   8 int cmd2process_cmp(const void *unused_cmp_data,
   9                     const struct subprocess_entry *e1,
  10                     const struct subprocess_entry *e2,
  11                     const void *unused_keydata)
  12 {
  13         return strcmp(e1->cmd, e2->cmd);
  14 }
  15
  16 struct subprocess_entry *subprocess_find_entry(struct hashmap *hashmap, const char *cmd)
  17 {
  18         struct subprocess_entry key;
  19
  20         hashmap_entry_init(&key, strhash(cmd));
  21         key.cmd = cmd;
  22         return hashmap_get(hashmap, &key, NULL);
  23 }
  24
  25 int subprocess_read_status(int fd, struct strbuf *status)
  26 {
  27         struct strbuf **pair;
  28         char *line;
  29         int len;
  30
  31         for (;;) {
  32                 len = packet_read_line_gently(fd, NULL, &line);
  33                 if ((len < 0) || !line)
  34                         break;
  35                 pair = strbuf_split_str(line, '=', 2);
  36                 if (pair[0] && pair[0]->len && pair[1]) {
  37                         /* the last "status=<foo>" line wins */
  38                         if (!strcmp(pair[0]->buf, "status=")) {
  39                                 strbuf_reset(status);
  40                                 strbuf_addbuf(status, pair[1]);
  41                         }
  42                 }
  43                 strbuf_list_free(pair);
  44         }
  45
  46         return (len < 0) ? len : 0;
  47 }
  48
  49 void subprocess_stop(struct hashmap *hashmap, struct subprocess_entry *entry)
  50 {
  51         if (!entry)
  52                 return;
  53
  54         entry->process.clean_on_exit = 0;
  55         kill(entry->process.pid, SIGTERM);
  56         finish_command(&entry->process);
  57
  58         hashmap_remove(hashmap, entry, NULL);
  59 }
  60
  61 static void subprocess_exit_handler(struct child_process *process)
  62 {
  63         sigchain_push(SIGPIPE, SIG_IGN);
  64         /* Closing the pipe signals the subprocess to initiate a shutdown. */
  65         close(process->in);
  66         close(process->out);
  67         sigchain_pop(SIGPIPE);
  68         /* Finish command will wait until the shutdown is complete. */
  69         finish_command(process);
  70 }
  71
  72 int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, const char *cmd,
  73         subprocess_start_fn startfn)
  74 {
  75         int err;
  76         struct child_process *process;
  77         const char *argv[] = { cmd, NULL };
  78
  79         entry->cmd = cmd;
  80         process = &entry->process;
  81
  82         child_process_init(process);
  83         process->argv = argv;
  84         process->use_shell = 1;
  85         process->in = -1;
  86         process->out = -1;
  87         process->clean_on_exit = 1;
  88         process->clean_on_exit_handler = subprocess_exit_handler;
  89
  90         err = start_command(process);
  91         if (err) {
  92                 error("cannot fork to run subprocess '%s'", cmd);
  93                 return err;
  94         }
  95
  96         hashmap_entry_init(entry, strhash(cmd));
  97
  98         err = startfn(entry);
  99         if (err) {
 100                 error("initialization for subprocess '%s' failed", cmd);
 101                 subprocess_stop(hashmap, entry);
 102                 return err;
 103         }
 104
 105         hashmap_add(hashmap, entry);
 106         return 0;
 107 }
 108
 109 static int handshake_version(struct child_process *process,
 110                              const char *welcome_prefix, int *versions,
 111                              int *chosen_version)
 112 {
 113         int version_scratch;
 114         int i;
 115         char *line;
 116         const char *p;
 117
 118         if (!chosen_version)
 119                 chosen_version = &version_scratch;
 120
 121         if (packet_write_fmt_gently(process->in, "%s-client\n",
 122                                     welcome_prefix))
 123                 return error("Could not write client identification");
 124         for (i = 0; versions[i]; i++) {
 125                 if (packet_write_fmt_gently(process->in, "version=%d\n",
 126                                             versions[i]))
 127                         return error("Could not write requested version");
 128         }
 129         if (packet_flush_gently(process->in))
 130                 return error("Could not write flush packet");
 131
 132         if (!(line = packet_read_line(process->out, NULL)) ||
 133             !skip_prefix(line, welcome_prefix, &p) ||
 134             strcmp(p, "-server"))
 135                 return error("Unexpected line '%s', expected %s-server",
 136                              line ? line : "<flush packet>", welcome_prefix);
 137         if (!(line = packet_read_line(process->out, NULL)) ||
 138             !skip_prefix(line, "version=", &p) ||
 139             strtol_i(p, 10, chosen_version))
 140                 return error("Unexpected line '%s', expected version",
 141                              line ? line : "<flush packet>");
 142         if ((line = packet_read_line(process->out, NULL)))
 143                 return error("Unexpected line '%s', expected flush", line);
 144
 145         /* Check to make sure that the version received is supported */
 146         for (i = 0; versions[i]; i++) {
 147                 if (versions[i] == *chosen_version)
 148                         break;
 149         }
 150         if (!versions[i])
 151                 return error("Version %d not supported", *chosen_version);
 152
 153         return 0;
 154 }
 155
 156 static int handshake_capabilities(struct child_process *process,
 157                                   struct subprocess_capability *capabilities,
 158                                   unsigned int *supported_capabilities)
 159 {
 160         int i;
 161         char *line;
 162
 163         for (i = 0; capabilities[i].name; i++) {
 164                 if (packet_write_fmt_gently(process->in, "capability=%s\n",
 165                                             capabilities[i].name))
 166                         return error("Could not write requested capability");
 167         }
 168         if (packet_flush_gently(process->in))
 169                 return error("Could not write flush packet");
 170
 171         while ((line = packet_read_line(process->out, NULL))) {
 172                 const char *p;
 173                 if (!skip_prefix(line, "capability=", &p))
 174                         continue;
 175
 176                 for (i = 0;
 177                      capabilities[i].name && strcmp(p, capabilities[i].name);
 178                      i++)
 179                         ;
 180                 if (capabilities[i].name) {
 181                         if (supported_capabilities)
 182                                 *supported_capabilities |= capabilities[i].flag;
 183                 } else {
 184                         warning("subprocess '%s' requested unsupported capability '%s'",
 185                                 process->argv[0], p);
 186                 }
 187         }
 188
 189         return 0;
 190 }
 191
 192 int subprocess_handshake(struct subprocess_entry *entry,
 193                          const char *welcome_prefix,
 194                          int *versions,
 195                          int *chosen_version,
 196                          struct subprocess_capability *capabilities,
 197                          unsigned int *supported_capabilities)
 198 {
 199         int retval;
 200         struct child_process *process = &entry->process;
 201
 202         sigchain_push(SIGPIPE, SIG_IGN);
 203
 204         retval = handshake_version(process, welcome_prefix, versions,
 205                                    chosen_version) ||
 206                  handshake_capabilities(process, capabilities,
 207                                         supported_capabilities);
 208
 209         sigchain_pop(SIGPIPE);
 210         return retval;
 211 }