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/*
* netlink_read_reply generic netlink response, for libreswan
*
* Copyright (C) 2012-2013 Kim B. Heino <b@bbbs.net>
* Copyright (C) 2024 Andrew Cagney
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <https://www.gnu.org/licenses/gpl2.txt>.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*/
#include <stdio.h>
#include <linux/rtnetlink.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include "linux_netlink.h"
#include "lsw_socket.h"
#include "lswalloc.h"
#include "lswlog.h"
/* ??? one caller thinks errno is meaningful after a failure */
static bool linux_netlink_process_response(const struct nlmsghdr *nlmsg, int sock,
linux_netlink_response_processor *processor,
struct linux_netlink_context *context,
struct verbose verbose)
{
for (;;) {
struct sockaddr_nl sa;
ssize_t readlen; /* signed */
union {
struct nlmsghdr nlhdr;
uint8_t raw[LINUX_NETLINK_BUFSIZE];
} buf;
/*
* Read netlink message, verifying kernel origin
* (in sa.nl_pid?)
*/
do {
socklen_t salen = sizeof(sa);
verbose("reading into %zu byte buffer", sizeof(buf));
errno = 0;
readlen = recvfrom(sock, &buf, sizeof(buf), 0,
(struct sockaddr *)&sa, &salen);
if (errno == EAGAIN) {
if (nlmsg->nlmsg_flags & NLM_F_ACK) {
continue; /* try again!?! */
}
return true;
}
if (readlen <= 0 || salen != sizeof(sa)) {
llog_errno(RC_LOG, verbose.logger, errno,
"read netlink socket failure: ");
return false;
}
} while (sa.nl_pid != 0);
verbose("processing %zu byte response", readlen);
/*
* Now process the contents.
*/
struct nlmsghdr *nlhdr = &buf.nlhdr;
verbose.level++;
do {
/*
* Check that READLEN is big enough to hold
* the current message.
*/
if (!NLMSG_OK(nlhdr, readlen)) {
verbose("TRUNCATED %zd", readlen);
return false;
}
if (nlhdr->nlmsg_type == NLMSG_ERROR) {
verbose("ERROR");
return false;
}
/*
* When there's a multi-part message, the last
* part has type NLMSG_DONE set.
*/
if (nlhdr->nlmsg_type == NLMSG_DONE) {
verbose("DONE");
return true;
}
/*
* Process this message (could be more).
* Processor is responsible for checking PID.
*/
if (nlhdr->nlmsg_seq == nlmsg->nlmsg_seq) {
if (!processor(nlhdr, context, verbose)) {
/* this means stop early; not
* a failure */
return true;
}
}
/*
* When NLM_F_MULTI is set there's another
* message following. It could be part of
* this read, but it could also be in the
* socket waiting for a read.
*/
if ((nlhdr->nlmsg_flags & NLM_F_MULTI) == 0) {
return true;
}
/*
* Advance to the next message in the buffer.
* If the buffer has been consumed, loop round
* the outer loop re-fill the buffer from the
* socket.
*/
nlhdr = NLMSG_NEXT(nlhdr, readlen);
} while (readlen > 0);
verbose.level--;
}
return true;
}
bool linux_netlink_query(const struct nlmsghdr *nlmsg, int netlink_protocol,
bool (*processor)(struct nlmsghdr *,
struct linux_netlink_context *,
struct verbose verbose),
struct linux_netlink_context *context,
struct verbose verbose)
{
/*
* When no ACK is required; open non-blocking so that read
* doesn't hang.
*/
unsigned flags = 0;
if (nlmsg->nlmsg_flags & NLM_F_ACK) {
verbose("opening blocking netlink socket");
} else {
verbose("opening non-blocking netlink socket");
flags |= SOCK_NONBLOCK;
}
int sock = cloexec_socket(PF_NETLINK, SOCK_DGRAM|flags, netlink_protocol);
if (sock < 0) {
llog_errno(RC_LOG, verbose.logger, errno,
"create netlink socket failure: ");
return false;
}
if (send(sock, nlmsg, nlmsg->nlmsg_len, 0) < 0) {
llog_errno(RC_LOG, verbose.logger, errno, "write netlink socket failure: ");
close(sock);
return false;
}
verbose("sent %d byte netlink message", (int)nlmsg->nlmsg_len);
bool ok = linux_netlink_process_response(nlmsg, sock,
processor, context,
verbose);
close(sock);
return ok;
}
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