quic upload improvements

[icing]

quic: various improvements

• set sockopt to receive ECN
• set socktop to dontfrag
• vquic: provide ECN on receive to callbacks
• ngtcp2: manage sendbuf more carefully, do not add more than QUIC can keep in flight

[icing]

@vszakats I need some help with cmake detecting <netinet/ip.h>. I tried to add the magic incantations to CMakeLists.txt, but it seems to have been a miss.

Update: found it!

[Copilot]

Pull request overview

Improves QUIC packet metadata handling and ngtcp2 upload buffering.

Changes:

• Enables ECN reception and IP fragmentation controls.
• Propagates ECN metadata through QUIC receive callbacks.
• Adds adaptive ngtcp2 in-flight upload limits.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
CMakeLists.txt	Detects netinet/ip.h.
configure.ac	Adds Autoconf header detection.
lib/curl_config-cmake.h.in	Exposes the header feature macro.
lib/cf-socket.c	Configures ECN and fragmentation socket options.
lib/vquic/vquic.c	Extracts and forwards received ECN metadata.
lib/vquic/vquic_int.h	Updates the receive callback ECN type.
lib/vquic/cf-quiche.c	Adopts the callback signature.
lib/vquic/cf-ngtcp2.c	Adds adaptive upload buffering.
lib/vquic/cf-ngtcp2-proxy.c	Renames in-flight tracking fields.
lib/vquic/cf-ngtcp2-cmn.h	Defines upload-buffer state and defaults.
lib/vquic/cf-ngtcp2-cmn.c	Initializes state and forwards ECN to ngtcp2.

Suppressed comments (1)

lib/vquic/vquic.c:905

• This receive path has the same ancillary-buffer regression as recvmmsg: with both IP_RECVTOS and UDP_GRO enabled, msg_ctrl has room for only one cmsg. Losing the GRO cmsg causes an aggregated datagram to be passed as a single QUIC packet. Allocate space for both the TOS and GRO control messages before extracting them here.

    ecn = vquic_msghdr_get_ecn(&msg, remote_addr.ss_family);

---

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[vszakats]

Suggested change

	#ifdef HAVE_NETINET_IP_H
	#include <netinet/ip.h>
	#endif

Since this isn't needed by other detections, we can drop this I think.

[icing]

I try if you think it's worth it. A bit stressed for time right now.

[vszakats]

We can prefill it for Windows and Unix (for CI) to save configure time:

--- a/CMake/unix-cache.cmake
+++ b/CMake/unix-cache.cmake
@@ -202,6 +202,7 @@ else()
   set(HAVE_NETINET_IN6_H 0)
 endif()
 set(HAVE_NETINET_IN_H 1)
+set(HAVE_NETINET_IP_H 1)
 set(HAVE_NETINET_TCP_H 1)
 set(HAVE_NETINET_UDP_H 1)
 set(HAVE_NET_IF_H 1)
--- a/CMake/win32-cache.cmake
+++ b/CMake/win32-cache.cmake
@@ -112,6 +112,7 @@ set(HAVE_MEMRCHR 0)
 set(HAVE_NETDB_H 0)
 set(HAVE_NETINET_IN6_H 0)
 set(HAVE_NETINET_IN_H 0)
+set(HAVE_NETINET_IP_H 0)
 set(HAVE_NETINET_TCP_H 0)
 set(HAVE_NETINET_UDP_H 0)
 set(HAVE_NET_IF_H 0)