Message-ID: <ejhphmjh74ebtk4br3id66f27a4yoh4aukrcz7m6dp7acsu6zr@crtueyadqzmp>
Date: Sun, 17 Mar 2024 09:55:50 -0400
From: Oliver Crumrine <ozlinuxc@...il.com>
To: alx@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-man@...r.kernel.org
Subject: [PATCH] ip.7: Add not supported by SOCK_STREAM to socket options

It was not made clear in several socket options that they were not
supported by SOCK_STREAM; this patch fixes that.

Socket options not supported by SOCK_STREAM are handled in the
ip_cmsg_recv_offset function in net/ipv4/ip_sockglue.c. The function is
called for udp sockets, and indirectly by ping and raw sockets, but not
for STREAM sockets, as they don't support these options.

Signed-off-by: Oliver Crumrine <ozlinuxc@...il.com>

v1->v2: Add IP_RETOPTS to the socket options without support on
SOCK_STREAM

Alex, I have attached the two test programs below, updated for support
with IP_RETOPTS.

I couldn't get an ip option out of netcat, so I'm attaching the client
programs, also updated with support for IP_OPTIONS, so they put an ip
option onto the packet for the server program to recieve.

Here is the diff between the two servers:
--- testDgramSocketServer.c     2024-03-17 08:32:27.623451419 -0400
+++ testStreamSocketServer.c    2024-03-17 08:21:11.860109033 -0400
@@ -23,7 +23,7 @@
        struct sockaddr_in local_addr;
        int s;

-       s = socket(AF_INET, SOCK_DGRAM, 0);
+       s = socket(AF_INET, SOCK_STREAM, 0);
        if (s == -1){
                err(1, "error creating socket");
        }
@@ -43,8 +43,20 @@
        if(bind(s, (struct sockaddr*)&local_addr, sizeof(local_addr) ) == -1){
                err(1, "error binding to port. try changing it or running as root");
        }
+
+       if(listen(s, 10) == -1){ //10 is the backlog of un-accepted connections. its just an arbitrary number
+               err(1, "error listening on port");
+       }

        while(1){
+               int connfd = accept(s, (struct sockaddr*)NULL, NULL);
+               if(connfd == -1){
+                       err(1, "error accepting connection");
+               }
+               if(setsockopt(s, IPPROTO_IP, SOCKOPT, &yes, sizeof(yes)) == -1){ //stream sockets should have this set on the connected socket as well. I left it above for uniformity between the two programs.
+                       err(1, "error setting socket option");
+               }
+
                struct msghdr mhdr;
                struct iovec iov[1];
                struct cmsghdr *cmhdr;
@@ -63,7 +75,7 @@
                memset(databuf, 0, sizeof(databuf));

                //this is blocking
-               int msglen = recvmsg(s, &mhdr, 0);
+               int msglen = recvmsg(connfd, &mhdr, 0);
                if (msglen == -1){
                        err(1, "recvmsg");
                }
@@ -78,6 +90,7 @@
                }
                //print out the first byte of data recieved in hex. You can verify this in wireshark if you like.
                printf("data read: %sbyte = %02X\n", databuf, tos);
+               close(connfd);
        }

        close(s);

And the clients in case you're interested:
--- testDgramSocketClient.c     2024-03-17 08:24:07.640111430 -0400
+++ testStreamSocketClient.c    2024-03-17 08:23:02.883443865 -0400
@@ -15,7 +15,7 @@

        char buf[] = "testing 1 2 3\n";

-       s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+       s = socket(AF_INET, SOCK_STREAM, 0);
        if(s == -1){
                err(1, "error creating socket");
        }
@@ -34,7 +34,10 @@
                err(1, "error converting network address");
        }

-       if(sendto(s, buf, strlen(buf), 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1){
+       if(connect(s, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1){
+               err(1, "error connecting");
+       }
+       if(send(s, buf, strlen(buf), 0) == -1){
                err(1, "error sending data");
        }

---
 man7/ip.7 | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/man7/ip.7 b/man7/ip.7
index 2b4b06324..39055d3cf 100644
--- a/man7/ip.7
+++ b/man7/ip.7
@@ -828,6 +828,9 @@ is not zero, the primary local address of the interface specified by the
 index overwrites
 .I ipi_spec_dst
 for the routing table lookup.
+Not supported for
+.B SOCK_STREAM
+sockets.
 .TP
 .BR IP_RECVERR " (since Linux 2.2)"
 .\" Precisely: since Linux 2.1.15
@@ -989,6 +992,9 @@ in which the kernel returns the original destination address
 of the datagram being received.
 The ancillary message contains a
 .IR "struct sockaddr_in" .
+Not supported for
+.B SOCK_STREAM
+sockets.
 .TP
 .BR IP_RECVTOS " (since Linux 2.2)"
 .\" Precisely: since Linux 2.1.68
@@ -998,6 +1004,9 @@ ancillary message is passed with incoming packets.
 It contains a byte which specifies the Type of Service/Precedence
 field of the packet header.
 Expects a boolean integer flag.
+Not supported for
+.B SOCK_STREAM
+sockets.
 .TP
 .BR IP_RECVTTL " (since Linux 2.2)"
 .\" Precisely: since Linux 2.1.68
@@ -1015,6 +1024,9 @@ Identical to
 .BR IP_RECVOPTS ,
 but returns raw unprocessed options with timestamp and route record
 options not filled in for this hop.
+Not supported for
+.B SOCK_STREAM
+sockets.
 .TP
 .BR IP_ROUTER_ALERT " (since Linux 2.2)"
 .\" Precisely: since Linux 2.1.68
-- 
2.44.0


View attachment "testDgramSocketClient.c" of type "text/plain" (1119 bytes)

View attachment "testDgramSocketServer.c" of type "text/plain" (2462 bytes)

View attachment "testStreamSocketClient.c" of type "text/plain" (1164 bytes)

View attachment "testStreamSocketServer.c" of type "text/plain" (2995 bytes)

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