Re: fix: recvfrom() error handling

[Peter Radisson <radisson97@web.de>]

V2:
* removed 1 empty line
* and changed wording to "content of" to make clear *addrlen is used.

To replicate the problem:

// intended use
struct sockaddr_in  sock_out;
int slen=sizeof(sock_out); //socklen_t
recv_len = recvfrom(s, buf, BUFLEN, 0, (struct sockaddr *) &sock_out,
&slen);

// error case
struct sockaddr_in  sock_out;
int slen=1;
recv_len = recvfrom(s, buf, BUFLEN, 0, (struct sockaddr *) &sock_out,
&slen);

funfact: this escapes the error handling in the linux kernel (no crash)
set slen=-1 and you get EINVAL.

hope that helps.

 From 056b50b50dca9f08d203d1d56fdcb6e84d228dba Mon Sep 17 00:00:00 2001
From: Peter Radisson <--show-origin>
Date: Thu, 27 Mar 2025 17:05:51 +0100
Subject: [PATCH] Be more verbose about recvfrom(2) error handling

Signed-off-by: Peter Radisson <--show-origin>
---
  man2/recv.2 | 16 ++++++++++++++++
  1 file changed, 16 insertions(+)

diff --git a/man2/recv.2 b/man2/recv.2
index 2659957a6..413c42271 100644
--- a/man2/recv.2
+++ b/man2/recv.2
@@ -293,6 +293,22 @@ The returned address is truncated if the buffer
provided is too small;
  in this case,
  .I addrlen
  will return a value greater than was supplied to the call.
+If
+.I src_addr
+is NULL
+.I addrlen
+will be ignored.
+If
+.I src_addr
+is not NULL and the content of
+.I addrlen
+is less than null the call will return with
+.IR EINVAL .
+If
+.I addrlen
+is less than sizeof struct sockaddr_in the src_addr will
+not be modified.
+
  .PP
  If the caller is not interested in the source address,
  .I src_addr
--
2.35.3