From 5699e4c2d470a12c922c4b7c86a8987837911626 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 7 Oct 2024 13:03:51 +0200
Subject: [PATCH 1/2] resolved: fix fastopen fallback

We should not invalidate the socket address size before we use it.

Fixes: #34579
---
 src/resolve/resolved-dns-stream.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/resolve/resolved-dns-stream.c b/src/resolve/resolved-dns-stream.c
index 8c1512006a..c3e825abf4 100644
--- a/src/resolve/resolved-dns-stream.c
+++ b/src/resolve/resolved-dns-stream.c
@@ -205,6 +205,7 @@ static int dns_stream_identify(DnsStream *s) {
 
 ssize_t dns_stream_writev(DnsStream *s, const struct iovec *iov, size_t iovcnt, int flags) {
         ssize_t m;
+        int r;
 
         assert(s);
         assert(iov);
@@ -224,12 +225,14 @@ ssize_t dns_stream_writev(DnsStream *s, const struct iovec *iov, size_t iovcnt,
 
                 m = sendmsg(s->fd, &hdr, MSG_FASTOPEN);
                 if (m < 0) {
-                        if (errno == EOPNOTSUPP) {
-                                s->tfo_salen = 0;
-                                if (connect(s->fd, &s->tfo_address.sa, s->tfo_salen) < 0)
-                                        return -errno;
+                        if (ERRNO_IS_NOT_SUPPORTED(errno)) {
+                                /* MSG_FASTOPEN not supported? Then try to connect() traditionally */
+                                r = RET_NERRNO(connect(s->fd, &s->tfo_address.sa, s->tfo_salen));
+                                s->tfo_salen = 0; /* connection is made */
+                                if (r < 0 && r != -EINPROGRESS)
+                                        return r;
 
-                                return -EAGAIN;
+                                return -EAGAIN; /* In case of EINPROGRESS, EAGAIN or success: return EAGAIN, so that caller calls us again */
                         }
                         if (errno == EINPROGRESS)
                                 return -EAGAIN;

From 86eb9b4f3837f96dd59abbc39e62979ede489f5a Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 7 Oct 2024 13:04:29 +0200
Subject: [PATCH 2/2] resolved: use SOCKADDR_LEN() where appropriate

---
 src/resolve/resolved-dns-stream.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/resolve/resolved-dns-stream.c b/src/resolve/resolved-dns-stream.c
index c3e825abf4..e57af66221 100644
--- a/src/resolve/resolved-dns-stream.c
+++ b/src/resolve/resolved-dns-stream.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <linux/if_arp.h>
 #include <netinet/tcp.h>
 #include <unistd.h>
 
@@ -568,7 +569,7 @@ int dns_stream_new(
 
         if (tfo_address) {
                 s->tfo_address = *tfo_address;
-                s->tfo_salen = tfo_address->sa.sa_family == AF_INET6 ? sizeof(tfo_address->in6) : sizeof(tfo_address->in);
+                s->tfo_salen = SOCKADDR_LEN(*tfo_address);
         }
 
         *ret = TAKE_PTR(s);