From 81143813a6b3ec297c31d234bbdc6000ed8c7052 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Thu, 24 Oct 2024 15:59:21 +1100 Subject: tcp: Generalise probing for tcpi_snd_wnd field In order to use the tcpi_snd_wnd field from the TCP_INFO getsockopt() we need the field to be supported in the runtime kernel (snd_wnd_cap). In fact we should check that for for every tcp_info field we want to use, beyond the very old ones shared with BSD. Prepare to do that, by generalising the probing from setting a single bool to instead record the size of the returned TCP_INFO structure. We can then use that recorded value to check for the presence of any field we need. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- tcp.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-) (limited to 'tcp.c') diff --git a/tcp.c b/tcp.c index 2a0b272..998e56d 100644 --- a/tcp.c +++ b/tcp.c @@ -361,10 +361,15 @@ char tcp_buf_discard [MAX_WINDOW]; /* Does the kernel support TCP_PEEK_OFF? */ bool peek_offset_cap; -/* Does the kernel report sending window in TCP_INFO (kernel commit - * 8f7baad7f035) - */ -bool snd_wnd_cap; +/* Size of data returned by TCP_INFO getsockopt() */ +socklen_t tcp_info_size; + +#define tcp_info_cap(f_) \ + ((offsetof(struct tcp_info_linux, tcpi_##f_) + \ + sizeof(((struct tcp_info_linux *)NULL)->tcpi_##f_)) <= tcp_info_size) + +/* Kernel reports sending window in TCP_INFO (kernel commit 8f7baad7f035) */ +#define snd_wnd_cap tcp_info_cap(snd_wnd) /* sendmsg() to socket */ static struct iovec tcp_iov [UIO_MAXIOV]; @@ -2571,11 +2576,11 @@ static bool tcp_probe_peek_offset_cap(sa_family_t af) } /** - * tcp_probe_snd_wnd_cap() - Check if TCP_INFO reports tcpi_snd_wnd + * tcp_probe_tcp_info() - Check what data TCP_INFO reports * - * Return: true if supported, false otherwise + * Return: Number of bytes returned by TCP_INFO getsockopt() */ -static bool tcp_probe_snd_wnd_cap(void) +static socklen_t tcp_probe_tcp_info(void) { struct tcp_info_linux tinfo; socklen_t sl = sizeof(tinfo); @@ -2595,11 +2600,7 @@ static bool tcp_probe_snd_wnd_cap(void) close(s); - if (sl < (offsetof(struct tcp_info_linux, tcpi_snd_wnd) + - sizeof(tinfo.tcpi_snd_wnd))) - return false; - - return true; + return sl; } /** @@ -2635,9 +2636,12 @@ int tcp_init(struct ctx *c) (!c->ifi6 || tcp_probe_peek_offset_cap(AF_INET6)); debug("SO_PEEK_OFF%ssupported", peek_offset_cap ? " " : " not "); - snd_wnd_cap = tcp_probe_snd_wnd_cap(); - debug("TCP_INFO tcpi_snd_wnd field%ssupported", - snd_wnd_cap ? " " : " not "); + tcp_info_size = tcp_probe_tcp_info(); + +#define dbg_tcpi(f_) debug("TCP_INFO tcpi_%s field%s supported", \ + STRINGIFY(f_), tcp_info_cap(f_) ? " " : " not ") + dbg_tcpi(snd_wnd); +#undef dbg_tcpi return 0; } -- cgit v1.2.3