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 hashmap_entry *eptr,
  10                     const struct hashmap_entry *entry_or_key,
  11                     const void *unused_keydata)
  12 {
  13         const struct subprocess_entry *e1, *e2;
  14
  15         e1 = container_of(eptr, const struct subprocess_entry, ent);
  16         e2 = container_of(entry_or_key, const struct subprocess_entry, ent);
  17
  18         return strcmp(e1->cmd, e2->cmd);
  19 }
  20
  21 struct subprocess_entry *subprocess_find_entry(struct hashmap *hashmap, const char *cmd)
  22 {
  23         struct subprocess_entry key;
  24
  25         hashmap_entry_init(&key.ent, strhash(cmd));
  26         key.cmd = cmd;
  27         return hashmap_get_entry(hashmap, &key, ent, NULL);
  28 }
  29
  30 int subprocess_read_status(int fd, struct strbuf *status)
  31 {
  32         struct strbuf **pair;
  33         char *line;
  34         int len;
  35
  36         for (;;) {
  37                 len = packet_read_line_gently(fd, NULL, &line);
  38                 if ((len < 0) || !line)
  39                         break;
  40                 pair = strbuf_split_str(line, '=', 2);
  41                 if (pair[0] && pair[0]->len && pair[1]) {
  42                         /* the last "status=<foo>" line wins */
  43                         if (!strcmp(pair[0]->buf, "status=")) {
  44                                 strbuf_reset(status);
  45                                 strbuf_addbuf(status, pair[1]);
  46                         }
  47                 }
  48                 strbuf_list_free(pair);
  49         }
  50
  51         return (len < 0) ? len : 0;
  52 }
  53
  54 void subprocess_stop(struct hashmap *hashmap, struct subprocess_entry *entry)
  55 {
  56         if (!entry)
  57                 return;
  58
  59         entry->process.clean_on_exit = 0;
  60         kill(entry->process.pid, SIGTERM);
  61         finish_command(&entry->process);
  62
  63         hashmap_remove(hashmap, &entry->ent, NULL);
  64 }
  65
  66 static void subprocess_exit_handler(struct child_process *process)
  67 {
  68         sigchain_push(SIGPIPE, SIG_IGN);
  69         /* Closing the pipe signals the subprocess to initiate a shutdown. */
  70         close(process->in);
  71         close(process->out);
  72         sigchain_pop(SIGPIPE);
  73         /* Finish command will wait until the shutdown is complete. */
  74         finish_command(process);
  75 }
  76
  77 int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, const char *cmd,
  78         subprocess_start_fn startfn)
  79 {
  80         int err;
  81         struct child_process *process;
  82
  83         entry->cmd = cmd;
  84         process = &entry->process;
  85
  86         child_process_init(process);
  87         strvec_push(&process->args, cmd);
  88         process->use_shell = 1;
  89         process->in = -1;
  90         process->out = -1;
  91         process->clean_on_exit = 1;
  92         process->clean_on_exit_handler = subprocess_exit_handler;
  93         process->trace2_child_class = "subprocess";
  94
  95         err = start_command(process);
  96         if (err) {
  97                 error("cannot fork to run subprocess '%s'", cmd);
  98                 return err;
  99         }
 100
 101         hashmap_entry_init(&entry->ent, strhash(cmd));
 102
 103         err = startfn(entry);
 104         if (err) {
 105                 error("initialization for subprocess '%s' failed", cmd);
 106                 subprocess_stop(hashmap, entry);
 107                 return err;
 108         }
 109
 110         hashmap_add(hashmap, &entry->ent);
 111         return 0;
 112 }
 113
 114 static int handshake_version(struct child_process *process,
 115                              const char *welcome_prefix, int *versions,
 116                              int *chosen_version)
 117 {
 118         int version_scratch;
 119         int i;
 120         char *line;
 121         const char *p;
 122
 123         if (!chosen_version)
 124                 chosen_version = &version_scratch;
 125
 126         if (packet_write_fmt_gently(process->in, "%s-client\n",
 127                                     welcome_prefix))
 128                 return error("Could not write client identification");
 129         for (i = 0; versions[i]; i++) {
 130                 if (packet_write_fmt_gently(process->in, "version=%d\n",
 131                                             versions[i]))
 132                         return error("Could not write requested version");
 133         }
 134         if (packet_flush_gently(process->in))
 135                 return error("Could not write flush packet");
 136
 137         if (!(line = packet_read_line(process->out, NULL)) ||
 138             !skip_prefix(line, welcome_prefix, &p) ||
 139             strcmp(p, "-server"))
 140                 return error("Unexpected line '%s', expected %s-server",
 141                              line ? line : "<flush packet>", welcome_prefix);
 142         if (!(line = packet_read_line(process->out, NULL)) ||
 143             !skip_prefix(line, "version=", &p) ||
 144             strtol_i(p, 10, chosen_version))
 145                 return error("Unexpected line '%s', expected version",
 146                              line ? line : "<flush packet>");
 147         if ((line = packet_read_line(process->out, NULL)))
 148                 return error("Unexpected line '%s', expected flush", line);
 149
 150         /* Check to make sure that the version received is supported */
 151         for (i = 0; versions[i]; i++) {
 152                 if (versions[i] == *chosen_version)
 153                         break;
 154         }
 155         if (!versions[i])
 156                 return error("Version %d not supported", *chosen_version);
 157
 158         return 0;
 159 }
 160
 161 static int handshake_capabilities(struct child_process *process,
 162                                   struct subprocess_capability *capabilities,
 163                                   unsigned int *supported_capabilities)
 164 {
 165         int i;
 166         char *line;
 167
 168         for (i = 0; capabilities[i].name; i++) {
 169                 if (packet_write_fmt_gently(process->in, "capability=%s\n",
 170                                             capabilities[i].name))
 171                         return error("Could not write requested capability");
 172         }
 173         if (packet_flush_gently(process->in))
 174                 return error("Could not write flush packet");
 175
 176         while ((line = packet_read_line(process->out, NULL))) {
 177                 const char *p;
 178                 if (!skip_prefix(line, "capability=", &p))
 179                         continue;
 180
 181                 for (i = 0;
 182                      capabilities[i].name && strcmp(p, capabilities[i].name);
 183                      i++)
 184                         ;
 185                 if (capabilities[i].name) {
 186                         if (supported_capabilities)
 187                                 *supported_capabilities |= capabilities[i].flag;
 188                 } else {
 189                         die("subprocess '%s' requested unsupported capability '%s'",
 190                             process->argv[0], p);
 191                 }
 192         }
 193
 194         return 0;
 195 }
 196
 197 int subprocess_handshake(struct subprocess_entry *entry,
 198                          const char *welcome_prefix,
 199                          int *versions,
 200                          int *chosen_version,
 201                          struct subprocess_capability *capabilities,
 202                          unsigned int *supported_capabilities)
 203 {
 204         int retval;
 205         struct child_process *process = &entry->process;
 206
 207         sigchain_push(SIGPIPE, SIG_IGN);
 208
 209         retval = handshake_version(process, welcome_prefix, versions,
 210                                    chosen_version) ||
 211                  handshake_capabilities(process, capabilities,
 212                                         supported_capabilities);
 213
 214         sigchain_pop(SIGPIPE);
 215         return retval;
 216 }