[PATCH 1/6] tcp: support writing to a socket in listening state
From: Jeremy Harris <hidden>
Date: 2025-05-16 15:56:04
Also in:
netdev
Subsystem:
networking [general], networking [sockets], networking [tcp], performance events subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Neal Cardwell, Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Linus Torvalds
In the tcp sendmsg handler, permit a write in LISTENING state if a MSG_PRELOAD flag is used. Copy from iovec to a linear sk_buff for placement on the socket write queue. Signed-off-by: Jeremy Harris <redacted> --- include/linux/socket.h | 1 + net/ipv4/tcp.c | 17 +++++++++++++---- tools/perf/trace/beauty/include/linux/socket.h | 1 + tools/perf/trace/beauty/msg_flags.c | 3 +++ 4 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 3b262487ec06..b41f4cd4dc97 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h@@ -330,6 +330,7 @@ struct ucred { #define MSG_SOCK_DEVMEM 0x2000000 /* Receive devmem skbs as cmsg */ #define MSG_ZEROCOPY 0x4000000 /* Use user data in kernel path */ #define MSG_SPLICE_PAGES 0x8000000 /* Splice the pages from the iterator in sendmsg() */ +#define MSG_PRELOAD 0x10000000 /* Preload tx data while listening */ #define MSG_FASTOPEN 0x20000000 /* Send data in TCP SYN */ #define MSG_CMSG_CLOEXEC 0x40000000 /* Set close_on_exec for file descriptor received through
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b7b6ab41b496..72b5d7cad351 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c@@ -1136,12 +1136,13 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) tcp_rate_check_app_limited(sk); /* is sending application-limited? */ - /* Wait for a connection to finish. One exception is TCP Fast Open + /* Wait for a connection to finish. Exceptions are TCP Fast Open * (passive side) where data is allowed to be sent before a connection - * is fully established. + * is fully established, and a message marked as preload which is + * allowed to be placed in the send queue of a listening socket. */ if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) && - !tcp_passive_fastopen(sk)) { + !tcp_passive_fastopen(sk) && !(flags & MSG_PRELOAD)) { err = sk_stream_wait_connect(sk, &timeo); if (err != 0) goto do_error;
@@ -1226,7 +1227,13 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) if (copy > msg_data_left(msg)) copy = msg_data_left(msg); - if (zc == 0) { + if (unlikely(flags & MSG_PRELOAD)) { + copy = min_t(int, copy, skb_tailroom(skb)); + err = skb_add_data_nocache(sk, skb, &msg->msg_iter, + copy); + if (err) + goto do_error; + } else if (zc == 0) { bool merge = true; int i = skb_shinfo(skb)->nr_frags; struct page_frag *pfrag = sk_page_frag(sk);
@@ -1330,6 +1337,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) if (!msg_data_left(msg)) { if (unlikely(flags & MSG_EOR)) TCP_SKB_CB(skb)->eor = 1; + if (unlikely(flags & MSG_PRELOAD)) + goto out_nopush; goto out; }
diff --git a/tools/perf/trace/beauty/include/linux/socket.h b/tools/perf/trace/beauty/include/linux/socket.h
index c3322eb3d686..e9ea498169f3 100644
--- a/tools/perf/trace/beauty/include/linux/socket.h
+++ b/tools/perf/trace/beauty/include/linux/socket.h@@ -330,6 +330,7 @@ struct ucred { #define MSG_SOCK_DEVMEM 0x2000000 /* Receive devmem skbs as cmsg */ #define MSG_ZEROCOPY 0x4000000 /* Use user data in kernel path */ #define MSG_SPLICE_PAGES 0x8000000 /* Splice the pages from the iterator in sendmsg() */ +#define MSG_PRELOAD 0x10000000 /* Preload tx data while listening */ #define MSG_FASTOPEN 0x20000000 /* Send data in TCP SYN */ #define MSG_CMSG_CLOEXEC 0x40000000 /* Set close_on_exec for file descriptor received through
diff --git a/tools/perf/trace/beauty/msg_flags.c b/tools/perf/trace/beauty/msg_flags.c
index 2da581ff0c80..27e40da9b02d 100644
--- a/tools/perf/trace/beauty/msg_flags.c
+++ b/tools/perf/trace/beauty/msg_flags.c@@ -20,6 +20,9 @@ #ifndef MSG_SPLICE_PAGES #define MSG_SPLICE_PAGES 0x8000000 #endif +#ifndef MSG_PRELOAD +#define MSG_PRELOAD 0x10000000 +#endif #ifndef MSG_FASTOPEN #define MSG_FASTOPEN 0x20000000 #endif
--
2.49.0