23 lines
940 B
C++
23 lines
940 B
C++
#pragma once
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#include <linux/rtnetlink.h>
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template<class Request>
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inline void addRouterAttribute(Request& r,
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int type,
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const void* data,
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size_t size) {
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// Calculate the offset into the character buffer where the RTA data lives
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// We use offsetof on the buffer to get it. This avoids undefined behavior
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// by casting the buffer (which is safe because it's char) instead of the
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// Request struct.(which is undefined because of aliasing)
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size_t offset = NLMSG_ALIGN(r.hdr.nlmsg_len) - offsetof(Request, buf);
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auto attr = reinterpret_cast<struct rtattr*>(r.buf + offset);
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attr->rta_type = type;
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attr->rta_len = RTA_LENGTH(size);
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memcpy(RTA_DATA(attr), data, size);
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// Update the message length to include the router attribute.
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r.hdr.nlmsg_len = NLMSG_ALIGN(r.hdr.nlmsg_len) + RTA_ALIGN(attr->rta_len);
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}
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