File util-linux-agetty-netlink.patch of Package util-linux
From 1ddc84875c150ca7c142adba9bfcd4bf4323a3c4 Mon Sep 17 00:00:00 2001
From: Stanislav Brabec <sbrabec@suse.cz>
Date: Wed, 9 Jul 2025 14:35:28 +0200
Subject: [PATCH 2/2] agetty: Implement netlink based IP processing
References: https://github.com/util-linux/util-linux/pull/3649
The current \4 and \6 issue file escapes implementation is inferior. It
uses get getifaddrs() to get a list of IP addresses. This function does not
provide enough information to discriminate between stable IP addresses and
ephemeral addresses. As a result, especially \6 often gives unreliable
results.
The code is actually unable to get list of all interfaces, so a proper out
of the box IP address reporting depends on external tools that generate
issue file with the interfaces list.
The netlink messages are already used, but only as a change notifier. The
contents is not used, even if it contains exact information about the
change. As a result, change processing is triggered even for unrelated
network changes like IPv6 router advertisement.
The new implementation uses the new netaddrq library. It reports more
reliable results especially for IPv6.
Additionally, two new escapes are implemented:
\a Report all interfaces and assigned addresses that are considered as
reliable.
\A Report all interfaces and all assigned addresses.
TODO:
To prevent overflooding of the console, the list is currently limited to 12
interfaces. It would be nice to make it configurable.
Two pass processing of issue files. First pass just collects IP protocols
and list of interfaces (in future interface patterns). Now it always
processes both IPv4 and IPv6 on all interfaces. Not so bad, as \a is smart
enough to display just the useful part.
Maybe implement more options and formatting support for \a and \A.
Maybe implement interface filter globs or regexps for \a and \A. Still not
so bad, as \a automatically skips interfaces without reliable addresses
(e. g. lo or TUN).
Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
---
term-utils/agetty.8.adoc | 6 +
term-utils/agetty.c | 414 ++++++++++++++++++++++-----------------
2 files changed, 244 insertions(+), 176 deletions(-)
diff --git a/term-utils/agetty.8.adoc b/term-utils/agetty.8.adoc
index a33f12a3f..6670498f5 100644
--- a/term-utils/agetty.8.adoc
+++ b/term-utils/agetty.8.adoc
@@ -253,6 +253,12 @@ Insert the IPv4 address of the specified network interface (for example: \4\{eth
6 or 6{_interface_}::
The same as \4 but for IPv6.
+a::
+Insert list of "good" IP addresses for all interfaces. It prints best candidates for remote login IP addresses: global and site addresses; if not available, temporary address with the longest lifetime, if not available, link address. Note that link addresses are printed with local interface name, but they has to be done with the interface name on the machine where they will be used.
+
+A::
+Insert list of all IP addresses for all interfaces.
+
b::
Insert the baudrate of the current line.
diff --git a/term-utils/agetty.c b/term-utils/agetty.c
index f65e511ca..1f5d937e4 100644
--- a/term-utils/agetty.c
+++ b/term-utils/agetty.c
@@ -32,10 +32,7 @@
#include <langinfo.h>
#include <grp.h>
#include <pwd.h>
-#include <arpa/inet.h>
#include <netdb.h>
-#include <ifaddrs.h>
-#include <net/if.h>
#include <sys/utsname.h>
#include "strutils.h"
@@ -50,6 +47,9 @@
#include "env.h"
#include "path.h"
#include "fileutils.h"
+#ifdef AGETTY_RELOAD
+#include "netaddrq.h"
+#endif
#include "logindefs.h"
@@ -144,7 +144,6 @@
# define AGETTY_RELOAD_FILENAME "/run/agetty.reload" /* trigger file */
# define AGETTY_RELOAD_FDNONE -2 /* uninitialized fd */
static int inotify_fd = AGETTY_RELOAD_FDNONE;
-static int netlink_fd = AGETTY_RELOAD_FDNONE;
static uint32_t netlink_groups;
#endif
@@ -154,6 +153,7 @@ struct issue {
size_t mem_sz;
#ifdef AGETTY_RELOAD
+ struct ul_nl_data nl;
char *mem_old;
#endif
unsigned int do_tcsetattr : 1,
@@ -1603,81 +1603,7 @@ done:
}
#ifdef AGETTY_RELOAD
-static void open_netlink(void)
-{
- struct sockaddr_nl addr = { 0, };
- int sock;
-
- if (netlink_fd != AGETTY_RELOAD_FDNONE)
- return;
-
- sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
- if (sock >= 0) {
- addr.nl_family = AF_NETLINK;
- addr.nl_pid = getpid();
- addr.nl_groups = netlink_groups;
- if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0)
- close(sock);
- else
- netlink_fd = sock;
- }
-}
-
-static int process_netlink_msg(int *triggered)
-{
- char buf[4096];
- struct sockaddr_nl snl;
- struct nlmsghdr *h;
- int rc;
-
- struct iovec iov = {
- .iov_base = buf,
- .iov_len = sizeof(buf)
- };
- struct msghdr msg = {
- .msg_name = &snl,
- .msg_namelen = sizeof(snl),
- .msg_iov = &iov,
- .msg_iovlen = 1,
- .msg_control = NULL,
- .msg_controllen = 0,
- .msg_flags = 0
- };
-
- rc = recvmsg(netlink_fd, &msg, MSG_DONTWAIT);
- if (rc < 0) {
- if (errno == EWOULDBLOCK || errno == EAGAIN)
- return 0;
-
- /* Failure, just stop listening for changes */
- close(netlink_fd);
- netlink_fd = AGETTY_RELOAD_FDNONE;
- return 0;
- }
-
- for (h = (struct nlmsghdr *)buf; NLMSG_OK(h, (unsigned int)rc); h = NLMSG_NEXT(h, rc)) {
- if (h->nlmsg_type == NLMSG_DONE ||
- h->nlmsg_type == NLMSG_ERROR) {
- close(netlink_fd);
- netlink_fd = AGETTY_RELOAD_FDNONE;
- return 0;
- }
-
- *triggered = 1;
- break;
- }
-
- return 1;
-}
-
-static int process_netlink(void)
-{
- int triggered = 0;
- while (process_netlink_msg(&triggered));
- return triggered;
-}
-
-static int wait_for_term_input(int fd)
+static int wait_for_term_input(struct issue *ie, int fd)
{
char buffer[sizeof(struct inotify_event) + NAME_MAX + 1];
fd_set rfds;
@@ -1711,9 +1637,9 @@ static int wait_for_term_input(int fd)
FD_SET(inotify_fd, &rfds);
nfds = max(nfds, inotify_fd);
}
- if (netlink_fd >= 0) {
- FD_SET(netlink_fd, &rfds);
- nfds = max(nfds, netlink_fd);
+ if (ie->nl.fd >= 0) {
+ FD_SET(ie->nl.fd, &rfds);
+ nfds = max(nfds, ie->nl.fd);
}
/* If waiting fails, just fall through, presumably reading input will fail */
@@ -1725,9 +1651,10 @@ static int wait_for_term_input(int fd)
}
- if (netlink_fd >= 0 && FD_ISSET(netlink_fd, &rfds)) {
- if (!process_netlink())
- continue;
+ if (ie->nl.fd >= 0 && FD_ISSET(ie->nl.fd, &rfds)) {
+ /* We are ignoring errors here to prevent unability of
+ * further processing. */
+ ul_nl_process(&(ie->nl), UL_NL_ASYNC, UL_NL_ONESHOT);
/* Just drain the inotify buffer */
} else if (inotify_fd >= 0 && FD_ISSET(inotify_fd, &rfds)) {
@@ -1937,11 +1864,44 @@ static void eval_issue_file(struct issue *ie,
struct options *op,
struct termios *tp)
{
-#ifdef AGETTY_RELOAD
- netlink_groups = 0;
-#endif
if (!(op->flags & F_ISSUE))
goto done;
+
+#ifdef AGETTY_RELOAD
+/* TODO:
+ * Two pass processing for eval_issue_file()
+ * Implement pass 1: Just evaluate list of netlink_groups (IP protocols) and
+ * intefaces to monitor.
+ * That is why again label is here: netlink_groups will be re-evaluated and
+ * dump will be performed again.
+ */
+ /* netlink_groups = 0; */
+ netlink_groups = RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR;
+
+ /* Already initialized? */
+ if (ie->nl.fd)
+ goto skip;
+ /* Prepare netlink. */
+ ul_nl_init(&(ie->nl));
+ if ((ul_netaddrq_init(&(ie->nl), NULL, NULL, (void *)ie)))
+ goto skip;
+
+ /* Open netlink and create address list. */
+ if (ul_nl_open(&(ie->nl),
+ RTMGRP_LINK | netlink_groups))
+ goto skip;
+ if (ul_nl_request_dump(&(ie->nl), RTM_GETADDR))
+ goto error;
+ if (ul_nl_process(&(ie->nl), UL_NL_SYNC, UL_NL_LOOP) != UL_NL_DONE)
+ goto error;
+ goto skip;
+error:
+ /* In case of any error, the addrq list is just empty, and we can use
+ * the code without any error checking. */
+ ul_nl_close(&(ie->nl));
+ ie->nl.fd = 0;
+skip:
+#endif
/*
* The custom issue file or directory list specified by:
* agetty --issue-file <path[:path]...>
@@ -1986,11 +1946,6 @@ static void eval_issue_file(struct issue *ie,
issuedir_read(ie, _PATH_SYSCONFSTATICDIR "/" _PATH_ISSUE_DIRNAME, op, tp);
done:
-
-#ifdef AGETTY_RELOAD
- if (netlink_groups != 0)
- open_netlink();
-#endif
if (ie->output) {
fclose(ie->output);
ie->output = NULL;
@@ -2032,13 +1987,19 @@ again:
puts(_("[press ENTER to login]"));
#ifdef AGETTY_RELOAD
/* reload issue */
- if (!wait_for_term_input(STDIN_FILENO)) {
+ if (!wait_for_term_input(ie, STDIN_FILENO)) {
eval_issue_file(ie, op, tp);
if (issue_is_changed(ie)) {
if ((op->flags & F_VCONSOLE)
&& (op->flags & F_NOCLEAR) == 0)
termio_clear(STDOUT_FILENO);
- goto again;
+ {
+ /* TODO: Close to set netlink_groups again using pass 1 */
+ /* if (ie->nl.fd) ul_nl_close(&(ie->nl));
+ * ie->nl.fd = NULL; */
+
+ goto again;
+ }
}
}
#endif
@@ -2168,7 +2129,7 @@ static char *get_logname(struct issue *ie, struct options *op, struct termios *t
no_reload:
#ifdef AGETTY_RELOAD
- if (!wait_for_term_input(STDIN_FILENO)) {
+ if (!wait_for_term_input(ie, STDIN_FILENO)) {
/* refresh prompt -- discard input data, clear terminal
* and call do_prompt() again
*/
@@ -2177,6 +2138,8 @@ static char *get_logname(struct issue *ie, struct options *op, struct termios *t
eval_issue_file(ie, op, tp);
if (!issue_is_changed(ie))
goto no_reload;
+ /* if (ie->nl.fd) ul_nl_close(&(ie->nl));
+ * ie->nl.fd = NULL; */
tcflush(STDIN_FILENO, TCIFLUSH);
if ((op->flags & F_VCONSOLE)
&& (op->flags & F_NOCLEAR) == 0)
@@ -2576,92 +2539,170 @@ static void log_warn(const char *fmt, ...)
va_end(ap);
}
-static void print_addr(struct issue *ie, sa_family_t family, void *addr)
+static void print_iface_best(struct issue *ie,
+ const char *ifname,
+ uint8_t ifa_family)
{
- char buff[INET6_ADDRSTRLEN + 1];
+ struct ul_netaddrq_ip *best[__ULNETLINK_RATING_MAX];
+ struct ul_netaddrq_iface *ifaceq;
+ struct list_head *l;
+ enum ul_netaddrq_ip_rating threshold;
- inet_ntop(family, addr, buff, sizeof(buff));
- fprintf(ie->output, "%s", buff);
-}
+ if (!ie->nl.data_addr)
+ return; /* error: init failed */
-/*
- * Prints IP for the specified interface (@iface), if the interface is not
- * specified then prints the "best" one (UP, RUNNING, non-LOOPBACK). If not
- * found the "best" interface then prints at least host IP.
- */
-static void output_iface_ip(struct issue *ie,
- struct ifaddrs *addrs,
- const char *iface,
- sa_family_t family)
-{
- struct ifaddrs *p;
- struct addrinfo hints, *info = NULL;
- char *host = NULL;
- void *addr = NULL;
+ if ((ifaceq = ul_netaddrq_iface_by_name(&(ie->nl), ifname)))
+ {
+ memset(best, 0, sizeof(best));
+ if (ifa_family == AF_INET)
+ l = &(ifaceq->ip_quality_list_4);
+ else
+ /* if (ifa_family == AF_INET6) */
+ l = &(ifaceq->ip_quality_list_6);
- if (!addrs)
- return;
+ threshold =
+ ul_netaddrq_iface_bestaddr(l, &best);
+ if (best[threshold])
+ fputs(ul_nl_addr_ntop_address(best[threshold]->addr),
+ ie->output);
+ }
+}
- for (p = addrs; p; p = p->ifa_next) {
+static void print_addrq_bestofall(struct issue *ie,
+ uint8_t ifa_family)
+{
+ struct ul_netaddrq_iface *best_ifaceq;
+ enum ul_netaddrq_ip_rating threshold;
+ const char *best_ipp;
- if (!p->ifa_name ||
- !p->ifa_addr ||
- p->ifa_addr->sa_family != family)
- continue;
+ if (!ie->nl.data_addr)
+ return; /* error: init failed */
- if (iface) {
- /* Filter out by interface name */
- if (strcmp(p->ifa_name, iface) != 0)
- continue;
- } else {
- /* Select the "best" interface */
- if ((p->ifa_flags & IFF_LOOPBACK) ||
- !(p->ifa_flags & IFF_UP) ||
- !(p->ifa_flags & IFF_RUNNING))
- continue;
- }
+ best_ipp = ul_netaddrq_get_best_ipp(&(ie->nl), ifa_family,
+ &threshold, &best_ifaceq);
+ if (best_ipp)
+ fputs(best_ipp, ie->output);
+}
- addr = NULL;
- switch (p->ifa_addr->sa_family) {
- case AF_INET:
- addr = &((struct sockaddr_in *) p->ifa_addr)->sin_addr;
- break;
- case AF_INET6:
- addr = &((struct sockaddr_in6 *) p->ifa_addr)->sin6_addr;
- break;
+static void dump_iface_good(struct issue *ie,
+ struct ul_netaddrq_iface *ifaceq)
+{
+ struct ul_netaddrq_ip *best4[__ULNETLINK_RATING_MAX];
+ struct ul_netaddrq_ip *best6[__ULNETLINK_RATING_MAX];
+ struct list_head *li;
+ enum ul_netaddrq_ip_rating threshold = __ULNETLINK_RATING_MAX - 1;
+ enum ul_netaddrq_ip_rating fthreshold; /* per family threshold */
+ bool first = true;
+
+ memset(best4, 0, sizeof(best4));
+ threshold = ul_netaddrq_iface_bestaddr(&(ifaceq->ip_quality_list_4),
+ &best4);
+ memset(best6, 0, sizeof(best6));
+ fthreshold = ul_netaddrq_iface_bestaddr(&(ifaceq->ip_quality_list_6),
+ &best6);
+ if (fthreshold < threshold)
+ threshold = fthreshold;
+
+ list_for_each(li, &(ifaceq->ip_quality_list_4))
+ {
+ struct ul_netaddrq_ip *ipq;
+
+ ipq = list_entry(li, struct ul_netaddrq_ip, entry);
+ if (threshold <= ULNETLINK_RATING_SCOPE_LINK &&
+ ( ipq->quality <= threshold ||
+ /* Consider site addresses equally good as global */
+ ipq->quality == ULNETLINK_RATING_SCOPE_SITE) &&
+ best4[threshold])
+ {
+ if (first)
+ {
+ fprintf(ie->output, "%s: ", ifaceq->ifname);
+ first = false;
+ }
+ else
+ fprintf(ie->output, " ");
+ /* Write only the longest living temporary address */
+ if (threshold == ULNETLINK_RATING_F_TEMPORARY)
+ {
+ fputs(ul_nl_addr_ntop_address(best4[ULNETLINK_RATING_F_TEMPORARY]->addr),
+ ie->output);
+ goto temp_cont4;
+ }
+ else
+ fputs(ul_nl_addr_ntop_address(ipq->addr),
+ ie->output);
}
+ temp_cont4:;
+ }
- if (addr) {
- print_addr(ie, family, addr);
- return;
+ list_for_each(li, &(ifaceq->ip_quality_list_6))
+ {
+ struct ul_netaddrq_ip *ipq;
+
+ ipq = list_entry(li, struct ul_netaddrq_ip, entry);
+ if (threshold <= ULNETLINK_RATING_SCOPE_LINK &&
+ ( ipq->quality <= threshold ||
+ /* Consider site addresses equally good as global */
+ ipq->quality == ULNETLINK_RATING_SCOPE_SITE) &&
+ best6[threshold])
+ {
+ if (first)
+ {
+ fprintf(ie->output, "%s: ", ifaceq->ifname);
+ first = false;
+ }
+ else
+ fprintf(ie->output, " ");
+ /* Write only the longest living temporary address */
+ if (threshold == ULNETLINK_RATING_F_TEMPORARY)
+ {
+ fputs(ul_nl_addr_ntop_address(best6[ULNETLINK_RATING_F_TEMPORARY]->addr),
+ ie->output);
+ goto temp_cont6;
+ }
+ else
+ fputs(ul_nl_addr_ntop_address(ipq->addr),
+ ie->output);
}
+ temp_cont6:;
}
+ if (!first)
+ fputs("\n", ie->output);
+}
- if (iface)
- return;
+static void dump_iface_all(struct issue *ie,
+ struct ul_netaddrq_iface *ifaceq)
+{
+ struct list_head *li;
+ struct ul_netaddrq_ip *ipq;
+ bool first = true;
- /* Hmm.. not found the best interface, print host IP at least */
- memset(&hints, 0, sizeof(hints));
- hints.ai_family = family;
- if (family == AF_INET6)
- hints.ai_flags = AI_V4MAPPED;
-
- host = xgethostname();
- if (host && getaddrinfo(host, NULL, &hints, &info) == 0 && info) {
- switch (info->ai_family) {
- case AF_INET:
- addr = &((struct sockaddr_in *) info->ai_addr)->sin_addr;
- break;
- case AF_INET6:
- addr = &((struct sockaddr_in6 *) info->ai_addr)->sin6_addr;
- break;
+ list_for_each(li, &(ifaceq->ip_quality_list_4))
+ {
+ ipq = list_entry(li, struct ul_netaddrq_ip, entry);
+ if (first)
+ {
+ fprintf(ie->output, "%s: ", ifaceq->ifname);
+ first = false;
}
- if (addr)
- print_addr(ie, family, addr);
-
- freeaddrinfo(info);
+ else
+ fprintf(ie->output, " ");
+ fputs(ul_nl_addr_ntop_address(ipq->addr), ie->output);
+ }
+ list_for_each(li, &(ifaceq->ip_quality_list_6))
+ {
+ ipq = list_entry(li, struct ul_netaddrq_ip, entry);
+ if (first)
+ {
+ fprintf(ie->output, "%s: ", ifaceq->ifname);
+ first = false;
+ }
+ else
+ fprintf(ie->output, " ");
+ fputs(ul_nl_addr_ntop_address(ipq->addr), ie->output);
}
- free(host);
+ if (!first)
+ fputs("\n", ie->output);
}
/*
@@ -2860,26 +2901,47 @@ static void output_special_char(struct issue *ie,
case '4':
case '6':
{
- sa_family_t family = c == '4' ? AF_INET : AF_INET6;
- struct ifaddrs *addrs = NULL;
- char iface[128];
-
- if (getifaddrs(&addrs))
- break;
+ char iface[IF_NAMESIZE];
+ uint8_t ifa_family = c == '4' ? AF_INET : AF_INET6;
if (get_escape_argument(fp, iface, sizeof(iface)))
- output_iface_ip(ie, addrs, iface, family);
+ print_iface_best(ie, iface, ifa_family);
else
- output_iface_ip(ie, addrs, NULL, family);
-
- freeifaddrs(addrs);
+ print_addrq_bestofall(ie, ifa_family);
+ /* TODO: Move to pass 1 */
if (c == '4')
netlink_groups |= RTMGRP_IPV4_IFADDR;
else
netlink_groups |= RTMGRP_IPV6_IFADDR;
break;
}
+ case 'a':
+ {
+ struct list_head *li;
+ struct ul_netaddrq_iface *ifaceq;
+
+ list_for_each_netaddrq_iface(li, &(ie->nl))
+ {
+ ifaceq = list_entry(li, struct ul_netaddrq_iface, entry);
+
+ dump_iface_good(ie, ifaceq);
+ }
+ }
+ break;
+ case 'A':
+ {
+ struct list_head *li;
+ struct ul_netaddrq_iface *ifaceq;
+
+ list_for_each_netaddrq_iface(li, &(ie->nl))
+ {
+ ifaceq = list_entry(li, struct ul_netaddrq_iface, entry);
+
+ dump_iface_all(ie, ifaceq);
+ }
+ }
+ break;
#endif
default:
putc(c, ie->output);
--
2.48.1
