The SYN flood message prints the listening port number, but with many
processes bound to the same port on different IPs, it's impossible to
tell which socket is the problem.
Add the listen IP address to the SYN flood message in the "IP.port"
format like most other tools (eg: tcpdump).
Each protcol's "any" address and a host address now look like:
Possible SYN flooding on port 0.0.0.0.9001.
Possible SYN flooding on port 127.0.0.1.9001.
Possible SYN flooding on port ::.9001.
Possible SYN flooding on port fc00::1.9001.
Signed-off-by: Jamie Bainbridge <[email protected]>
---
v2: Place IS_ENABLED() inside if condition c/o Andrew Lunn.
Change port printf to unsigned c/o Stephen Hemminger.
Remove long and unhelpful "Check SNMP counters" c/o Stephen.
Use IP.port format c/o Eric Dumazet.
---
net/ipv4/tcp_input.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0640453fce54b6daae0861d948f3db075830daf6..5b156dfc13b3d45c20e4fe6a45af7c42f39b2c66 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6831,9 +6831,17 @@ static bool tcp_syn_flood_action(const struct sock *sk, const char *proto)
__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
if (!queue->synflood_warned && syncookies != 2 &&
- xchg(&queue->synflood_warned, 1) == 0)
- net_info_ratelimited("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
- proto, sk->sk_num, msg);
+ xchg(&queue->synflood_warned, 1) == 0) {
+ if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
+ net_info_ratelimited("%s: Possible SYN flooding on port %pI6c.%u. %s.\n",
+ proto, &sk->sk_v6_rcv_saddr,
+ sk->sk_num, msg);
+ } else {
+ net_info_ratelimited("%s: Possible SYN flooding on port %pI4.%u. %s.\n",
+ proto, &sk->sk_rcv_saddr,
+ sk->sk_num, msg);
+ }
+ }
return want_cookie;
}
--
2.38.1
On Fri, 11 Nov 2022 14:59:32 +1100
Jamie Bainbridge <[email protected]> wrote:
> + xchg(&queue->synflood_warned, 1) == 0) {
> + if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> + net_info_ratelimited("%s: Possible SYN flooding on port %pI6c.%u. %s.\n",
> + proto, &sk->sk_v6_rcv_saddr,
> + sk->sk_num, msg);
> + } else {
> + net_info_ratelimited("%s: Possible SYN flooding on port %pI4.%u. %s.\n",
> + proto, &sk->sk_rcv_saddr,
> + sk->sk_num, msg);
Minor nit, the standard format for printing addresses would be to use colon seperator before port
if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
net_info_ratelimited("%s: Possible SYN flooding on [%pI6c]:%u. %s.\n",
proto, &sk->sk_v6_rcv_saddr, sk->sk_num, msg);
} else {
net_info_ratelimited("%s: Possible SYN flooding on %pI4:%u. %s.\n",
proto, &sk->sk_rcv_saddr, sk->sk_num, msg);
On Fri, Nov 11, 2022 at 4:11 PM Stephen Hemminger
<[email protected]> wrote:
>
> On Sat, 12 Nov 2022 10:59:52 +1100
> Jamie Bainbridge <[email protected]> wrote:
>
> > On Sat, 12 Nov 2022 at 04:20, Stephen Hemminger
> > <[email protected]> wrote:
> > >
> > > On Fri, 11 Nov 2022 14:59:32 +1100
> > > Jamie Bainbridge <[email protected]> wrote:
> > >
> > > > + xchg(&queue->synflood_warned, 1) == 0) {
> > > > + if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > > > + net_info_ratelimited("%s: Possible SYN flooding on port %pI6c.%u. %s.\n",
> > > > + proto, &sk->sk_v6_rcv_saddr,
> > > > + sk->sk_num, msg);
> > > > + } else {
> > > > + net_info_ratelimited("%s: Possible SYN flooding on port %pI4.%u. %s.\n",
> > > > + proto, &sk->sk_rcv_saddr,
> > > > + sk->sk_num, msg);
> > >
> > > Minor nit, the standard format for printing addresses would be to use colon seperator before port
> > >
> > > if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > > net_info_ratelimited("%s: Possible SYN flooding on [%pI6c]:%u. %s.\n",
> > > proto, &sk->sk_v6_rcv_saddr, sk->sk_num, msg);
> > > } else {
> > > net_info_ratelimited("%s: Possible SYN flooding on %pI4:%u. %s.\n",
> > > proto, &sk->sk_rcv_saddr, sk->sk_num, msg);
> >
> > I considered this too, though Eric suggested "IP.port" to match tcpdump.
>
> That works, if it happens I doubt it matters.
Note that "ss dst" really needs the [] notation for IPv6
ss -t dst "[::1]"
State Recv-Q Send-Q
Local Address:Port Peer Address:Port
Process
CLOSE-WAIT 1 0
[::1]:50584 [::1]:ipp
So we have inconsistency anyway...
As you said, no strong opinion.
On Sat, 12 Nov 2022 10:59:52 +1100
Jamie Bainbridge <[email protected]> wrote:
> On Sat, 12 Nov 2022 at 04:20, Stephen Hemminger
> <[email protected]> wrote:
> >
> > On Fri, 11 Nov 2022 14:59:32 +1100
> > Jamie Bainbridge <[email protected]> wrote:
> >
> > > + xchg(&queue->synflood_warned, 1) == 0) {
> > > + if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > > + net_info_ratelimited("%s: Possible SYN flooding on port %pI6c.%u. %s.\n",
> > > + proto, &sk->sk_v6_rcv_saddr,
> > > + sk->sk_num, msg);
> > > + } else {
> > > + net_info_ratelimited("%s: Possible SYN flooding on port %pI4.%u. %s.\n",
> > > + proto, &sk->sk_rcv_saddr,
> > > + sk->sk_num, msg);
> >
> > Minor nit, the standard format for printing addresses would be to use colon seperator before port
> >
> > if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > net_info_ratelimited("%s: Possible SYN flooding on [%pI6c]:%u. %s.\n",
> > proto, &sk->sk_v6_rcv_saddr, sk->sk_num, msg);
> > } else {
> > net_info_ratelimited("%s: Possible SYN flooding on %pI4:%u. %s.\n",
> > proto, &sk->sk_rcv_saddr, sk->sk_num, msg);
>
> I considered this too, though Eric suggested "IP.port" to match tcpdump.
That works, if it happens I doubt it matters.
On Fri, Nov 11, 2022 at 4:00 PM Jamie Bainbridge
<[email protected]> wrote:
>
> On Sat, 12 Nov 2022 at 04:20, Stephen Hemminger
> <[email protected]> wrote:
> >
> > On Fri, 11 Nov 2022 14:59:32 +1100
> > Jamie Bainbridge <[email protected]> wrote:
> >
> > > + xchg(&queue->synflood_warned, 1) == 0) {
> > > + if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > > + net_info_ratelimited("%s: Possible SYN flooding on port %pI6c.%u. %s.\n",
> > > + proto, &sk->sk_v6_rcv_saddr,
> > > + sk->sk_num, msg);
> > > + } else {
> > > + net_info_ratelimited("%s: Possible SYN flooding on port %pI4.%u. %s.\n",
> > > + proto, &sk->sk_rcv_saddr,
> > > + sk->sk_num, msg);
> >
> > Minor nit, the standard format for printing addresses would be to use colon seperator before port
> >
> > if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > net_info_ratelimited("%s: Possible SYN flooding on [%pI6c]:%u. %s.\n",
> > proto, &sk->sk_v6_rcv_saddr, sk->sk_num, msg);
> > } else {
> > net_info_ratelimited("%s: Possible SYN flooding on %pI4:%u. %s.\n",
> > proto, &sk->sk_rcv_saddr, sk->sk_num, msg);
>
> I considered this too, though Eric suggested "IP.port" to match tcpdump.
>
> Please let me know which advice to follow?
IPv6 [address]:port is also a standard (and unambiguous) way.
https://www.rfc-editor.org/rfc/rfc5952#page-11
On Sat, 12 Nov 2022 at 04:20, Stephen Hemminger
<[email protected]> wrote:
>
> On Fri, 11 Nov 2022 14:59:32 +1100
> Jamie Bainbridge <[email protected]> wrote:
>
> > + xchg(&queue->synflood_warned, 1) == 0) {
> > + if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > + net_info_ratelimited("%s: Possible SYN flooding on port %pI6c.%u. %s.\n",
> > + proto, &sk->sk_v6_rcv_saddr,
> > + sk->sk_num, msg);
> > + } else {
> > + net_info_ratelimited("%s: Possible SYN flooding on port %pI4.%u. %s.\n",
> > + proto, &sk->sk_rcv_saddr,
> > + sk->sk_num, msg);
>
> Minor nit, the standard format for printing addresses would be to use colon seperator before port
>
> if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> net_info_ratelimited("%s: Possible SYN flooding on [%pI6c]:%u. %s.\n",
> proto, &sk->sk_v6_rcv_saddr, sk->sk_num, msg);
> } else {
> net_info_ratelimited("%s: Possible SYN flooding on %pI4:%u. %s.\n",
> proto, &sk->sk_rcv_saddr, sk->sk_num, msg);
I considered this too, though Eric suggested "IP.port" to match tcpdump.
Please let me know which advice to follow?
Jamie
On Sat, 12 Nov 2022 at 10:14, Eric Dumazet <[email protected]> wrote:
>
> On Fri, Nov 11, 2022 at 4:11 PM Stephen Hemminger
> <[email protected]> wrote:
> >
> > On Sat, 12 Nov 2022 10:59:52 +1100
> > Jamie Bainbridge <[email protected]> wrote:
> >
> > > On Sat, 12 Nov 2022 at 04:20, Stephen Hemminger
> > > <[email protected]> wrote:
> > > >
> > > > On Fri, 11 Nov 2022 14:59:32 +1100
> > > > Jamie Bainbridge <[email protected]> wrote:
> > > >
> > > > > + xchg(&queue->synflood_warned, 1) == 0) {
> > > > > + if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > > > > + net_info_ratelimited("%s: Possible SYN flooding on port %pI6c.%u. %s.\n",
> > > > > + proto, &sk->sk_v6_rcv_saddr,
> > > > > + sk->sk_num, msg);
> > > > > + } else {
> > > > > + net_info_ratelimited("%s: Possible SYN flooding on port %pI4.%u. %s.\n",
> > > > > + proto, &sk->sk_rcv_saddr,
> > > > > + sk->sk_num, msg);
> > > >
> > > > Minor nit, the standard format for printing addresses would be to use colon seperator before port
> > > >
> > > > if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
> > > > net_info_ratelimited("%s: Possible SYN flooding on [%pI6c]:%u. %s.\n",
> > > > proto, &sk->sk_v6_rcv_saddr, sk->sk_num, msg);
> > > > } else {
> > > > net_info_ratelimited("%s: Possible SYN flooding on %pI4:%u. %s.\n",
> > > > proto, &sk->sk_rcv_saddr, sk->sk_num, msg);
> > >
> > > I considered this too, though Eric suggested "IP.port" to match tcpdump.
> >
> > That works, if it happens I doubt it matters.
>
> Note that "ss dst" really needs the [] notation for IPv6
>
> ss -t dst "[::1]"
> State Recv-Q Send-Q
> Local Address:Port Peer Address:Port
> Process
> CLOSE-WAIT 1 0
> [::1]:50584 [::1]:ipp
>
> So we have inconsistency anyway...
>
> As you said, no strong opinion.
Following an RFC and ss filter paste is a good reason, I'll do a v3.
Jamie