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Gleb Smirnoff 69c05f4287 udp: make sendto(2) on unconnected UDP socket use public inpcb KPIs 
UDP allows to sendto(2) on unconnected socket.  The original BSD devise
was that such action would create a temporary (for the duration of the
syscall) connection between our inpcb and remote addr:port specified in
sockaddr 'to' of the syscall.  This devise was broken in 2002 in
90162a4e87.  For more motivation on the removal of the temporary
connection see email [1].

Since the removal of the true temporary connection the sendto(2) on
unconnected socket has the following side effects:

1) After first sendto(2) the "unconnected" socket will receive datagrams
   destined to the selected port.
2) All subsequent sendto(2) calls will use the same source port.

Effectively, such sendto(2) acts like a bind(2) to INADDR_ANY:0.  Indeed,
if you do this:

	s1 = socket(PF_INET, SOCK_DGRAM, 0);
	s2 = socket(PF_INET, SOCK_DGRAM, 0);
	sendto(s1, ..., &somedestination, ...);
	bind(s2, &{ .sin_addr = INADDR_ANY, sin_port = 0 });

And then look into kgdb at resulting inpcbs, you would find them equal in
all means modulo bound to different anonymous ports.

What is even more interesting is that Linux kernel had picked up same
behavior, including that "unconnected" socket will receive datagrams.  So
it seems that such behavior is now an undocumented standard, thus I
covered it in recently added tests/sys/netinet/udp_bindings.

Now, with the above knowledge at hand, why are we using
in_pcbconnect_setup() and in_pcbinshash(), which are supposed to be
private to in_pcb.c, to achieve the binding?  Let's use public KPI
in_pcbbind() on the first sendto(2) and use in_pcbladdr() on all
sendto(2)s.  Apart from finally hiding these two should be private
functions, we no longer acquire global INP_HASH_WLOCK() for every
sendto(2) on unconnected socket as well as remove a couple workarounds.

[1] https://mail-archive.FreeBSD.org/cgi/mid.cgi?200210141935.aa83883

Reviewed by:		markj
Differential Revision:	https://reviews.freebsd.org/D49043
2025-02-21 18:11:17 -08:00
..
amd64
arm sys: Empty hints files 2025-02-21 17:25:32 -07:00
arm64 sys: Empty hints files 2025-02-21 17:25:32 -07:00
bsm
cam
cddl
compat
conf
contrib
crypto
ddb
dev qcom_ess_edma: Add the IPQ4018/IPQ4019 ethernet MAC/MDIO driver. 2025-02-20 18:48:12 -08:00
dts
fs vm_page: define partial page invalidate 2025-02-21 19:22:47 -06:00
gdb
geom
gnu
i386
isa
kern umtx: Fix a bug in do_lock_pp() 2025-02-22 01:26:38 +00:00
kgssapi
libkern
modules
net pf: make log(matches) more useful 2025-02-21 09:11:03 +01:00
net80211 net80211: crypto: ccmp: simplify and style(9) 2025-02-20 18:05:00 +00:00
netgraph
netinet udp: make sendto(2) on unconnected UDP socket use public inpcb KPIs 2025-02-21 18:11:17 -08:00
netinet6
netipsec
netlink
netpfil pf: Cut down on if statements around pf_icmp_state_lookup 2025-02-21 11:52:26 +01:00
netsmb
nfs
nfsclient
nfsserver
nlm
ofed
opencrypto
powerpc
riscv sys: Empty hints files 2025-02-21 17:25:32 -07:00
rpc
security
sys
teken
tests
tools
ufs
vm vm_page: define partial page invalidate 2025-02-21 19:22:47 -06:00
x86
xdr
xen
Makefile
README.md

README.md

FreeBSD Kernel Source:

This directory contains the source files and build glue that make up the FreeBSD kernel and its modules, including both original and contributed software.

Kernel configuration files are located in the conf/ subdirectory of each architecture. GENERIC is the configuration used in release builds. NOTES contains documentation of all possible entries. LINT is a compile-only configuration used to maximize build coverage and detect regressions.

Documentation:

Source code documentation is maintained in a set of man pages, under section 9. These pages are located in share/man/man9, from the top-level of the src tree. Consult intro(9) for an overview of existing pages.

Some additional high-level documentation of the kernel is maintained in the Architecture Handbook.

Source Roadmap:

Directory Description
amd64 AMD64 (64-bit x86) architecture support
arm 32-bit ARM architecture support
arm64 64-bit ARM (AArch64) architecture support
cam Common Access Method storage subsystem - cam(4) and ctl(4)
cddl CDDL-licensed optional sources such as DTrace
conf kernel build glue
compat Linux compatibility layer, FreeBSD 32-bit compatibility
contrib 3rd-party imported software such as OpenZFS
crypto crypto drivers
ddb interactive kernel debugger - ddb(4)
fs most filesystems, excluding UFS, NFS, and ZFS
dev device drivers and other arch independent code
gdb kernel remote GDB stub - gdb(4)
geom GEOM framework - geom(4)
i386 i386 (32-bit x86) architecture support
kern main part of the kernel
libkern libc-like and other support functions for kernel use
modules kernel module infrastructure
net core networking code
net80211 wireless networking (IEEE 802.11) - net80211(4)
netgraph graph-based networking subsystem - netgraph(4)
netinet IPv4 protocol implementation - inet(4)
netinet6 IPv6 protocol implementation - inet6(4)
netipsec IPsec protocol implementation - ipsec(4)
netpfil packet filters - ipfw(4), pf(4), and ipfilter(4)
opencrypto OpenCrypto framework - crypto(7)
powerpc PowerPC/POWER (32 and 64-bit) architecture support
riscv 64-bit RISC-V architecture support
security security facilities - audit(4) and mac(4)
sys kernel headers
tests kernel unit tests
ufs Unix File System - ffs(4)
vm virtual memory system
x86 code shared by AMD64 and i386 architectures