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/*
* Routine to provide information about the other side of a FD.
*
* Copyright (C) 2015 Peter Wu <peter@lekensteyn.nl>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*
*/
#define _GNU_SOURCE /* for struct ucred on Linux */
#include "scope.h"
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h> /* for pid_t */
static pid_t
GetPidFromFd(FD fd)
{
#ifdef SO_PEERCRED
struct ucred cred;
socklen_t cred_len = sizeof(cred);
if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cred, &cred_len) == 0 &&
cred_len == sizeof(cred)) {
return cred.pid;
}
#endif
return 0;
}
static const char *
GetProcnameForPid(pid_t pid)
{
/* comm is no longer than TASK_COMM_LEN (16) */
static char comm[17];
char comm_path[32];
char comm_fd;
unsigned comm_len = 0;
snprintf(comm_path, sizeof(comm_path), "/proc/%d/comm", pid);
comm_fd = open(comm_path, O_RDONLY);
if (comm_fd != -1) {
comm_len = read(comm_fd, comm, sizeof(comm) - 1);
if (comm_len < 0)
comm_len = 0;
close(comm_fd);
}
if (comm_len > 0 && comm[comm_len - 1] == '\n')
comm_len--;
comm[comm_len] = '\0';
return comm;
}
/*
Retrieves additional information about the other side of the fd.
For Unix domain sockets, this results in the process ID and name.
*/
char *
ReadPeerInfo(FD fd)
{
/* should hold enough for "PID <number> <command name>" */
char peer_info[40];
unsigned pos;
pid_t pid;
const char *comm;
pid = GetPidFromFd(fd);
/* Use the fact that pid_t is the first field of struct ucred. */
if (pid) {
pos = snprintf(peer_info, sizeof(peer_info), "pid %d", pid);
comm = GetProcnameForPid(pid);
if (comm)
pos += snprintf(peer_info + pos, sizeof(peer_info) - pos,
" %s", comm);
return strdup(peer_info);
}
/* (Could add port number here for AF_INET if it helps.) */
return NULL;
}
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